of stimulated raman scattering in different materials

CHARACTERIZATION OF STIMULATED

RAMAN SCATTERING IN DIFFERENT MATERIALS

Submitted by

GEORGE P MATHEW

Reg No: 95713003

A dissertion presented in partial fulfilment of the academic requirements for the award of the degree of

MASTER OF TECHNOLOGY

In OPTOELECTRONICS AND LASER TECHNOLOGY

INTERNATIONAL SCHOOL OF PHOTONICS COCHIN UNIVERSITY OF SCIENCE AND TECHNOLOGY

COCHIN - 682022

Under the guidance of

DR.V P N NAMPOORI EMERITUS PROFESSOR

INTERNATIONAL SCHOOL OF PHOTONICS

JUNE -2015

ACKNOWLEDGEMENT

I Thank ALMIGHTY GOD

With deep sense of gratitude, I express my heartfelt thanks to Dr.V P N Nampoori, Emeritus

Professor, International school of photonics, CUSAT for the guidance, motivation, support

and encouragement given throughout my project work.

I am thanking Dr M. Kailasnath, Director, International School of Photonics, CUSAT for

giving all facilities that helped me to complete this mission.

I extend my sincere thanks to Dr P. Radhakrishnan, Professor, International School of

Photonics, CUSAT for his motivation and support during my work

I am thankful to the research scholar of ISP Mr. Mathew S for his support and help.

I am thankful to my friends Mr. Sreejith S L, Mr. Faisal Khan, Ms. smrithi V and Ms.

Divya narayanan for their support and help.

I extend my sincere thanks to the teaching and non- teaching staff of ISP for all the help and

assistance.

I would like to express our gratitude and appreciation to all those who gave me the possibility

to complete this report.

I am extremely grateful to my family who were a constant source of encouragement.

GEORGE P MATHEW

ABSTRACT

Stimulated Raman scattering (SRS) has been well investigated in a variety of materials. It offers

a simple and inexpensive way of tuning the wavelength of a laser system. Addition of lasing dye

particularly for liquids that fluoresce at the Raman lines of the medium are used to reduce the

threshold of stimulated Raman process. In this paper we investigated backward SRS of Acetone,

Methanol, Xylene, Methyl Acetate and Demineralised Water. We examined the changes of SRS

when a dye (RHODAMINE 6G, Rhodamine B, Methylene Blue) added to this solvent. We also

examined the spectral evolution of the backward Raman emission at various pump intensities..

For SRS both emission wavelength and amplitudes are changing at threshold pump power and

amplitude is increasing for higher value of pump power. Optical phase conjugation has got

variety of application in now days. Optical phase conjugation can be created by forward mixing

and stimulated scattering. If the phase conjugation is created by the stimulated scattering the

properties of phase conjugation can be controlled by the medium properties since it is active

process and it has got an energy transfer between medium and the photon.

TABLE OF CONTENTS

SL NO. TOPIC PAGE NO

1 INTRODUCTION 1

2 RAMAN SCATTERING 6

3 APPLICATIONS OF STIMULATED RAMAN SCATTERING 10

4 CHARACTERIZATION OF SRS FOR DIFFERENT MATERIALS 11

5 RESEARCH MATERIALS 14

6 EXPERIMENT SET UP 23

7 OBSERVATIONS 34

8 RESULT AND ANALYSIS 65

9 CONCLUSION AND FUTURE WORK 73

10 REFERENCES 74

Characterization of stimulated Raman scattering in different materials

International school of Photonics, CUSAT 1

1. INTRODUCTION

Scattering is a general physical process where some forms of radiation, such as light,

sound, or moving particles, are forced to deviate from a straight trajectory by one or more paths

due to localized non-uniformities in the medium through which they pass. In conventional use,

this also includes deviation of reflected radiation from the angle predicted by the law of

reflection. Reflections that undergo scattering are often called diffuse reflections and unscattered

reflections are called specular (mirror-like) reflections.

Scattering may also refer to particle-particle collisions between molecules, atoms,

electrons, photons and other particles. Examples are: cosmic rays scattering by the Earth's upper

atmosphere; particle collisions inside particle accelerators; electron scattering by gas atoms in

fluorescent lamps; and neutron scattering inside nuclear reactors.

The types of non-uniformities which can cause scattering, sometimes known as scatterers

or scattering centers, are too numerous to list, but a small sample includes particles, bubbles,

droplets, density fluctuations in fluids, crystallites in polycrystalline solids, defects in

monocrystalline solids, surface roughness, cells in organisms, and textile fibers in clothing. The

effects of such features on the path of almost any type of propagating wave or moving particle

can be described in the framework of scattering theory.

Some areas where scattering and scattering theory are significant include radar sensing,

medical ultrasound, semiconductor wafer inspection, polymerization process monitoring,

acoustic tiling, free-space communications and computer-generated imagery. Particle-particle

scattering theory is important in areas such as particle physics, atomic, molecular, and optical

physics, nuclear physics and astrophysics.

SINGLE AND MULTIPLE SCATTERING

When radiation is only scattered by one localized scattering center, this is called single

scattering. It is very common that scattering centers are grouped together, and in those cases the



Radiation may scatter many times, which is known as multiple scattering. The main difference

between the effects of single and multiple scattering is that single scattering can usually be

treated as a random phenomenon and multiple scattering is usually more stochastic. Because the

location of a single scattering center is not usually well known relative to the path of the

radiation, the outcome, which tends to depend strongly on the exact incoming trajectory, appears

random to an observer. This type of scattering would be exemplified by an electron being fired at

an atomic nucleus. In that case, the atom's exact position relative to the path of the electron is

unknown and would be immeasurable, so the exact direction of the electron after the collision is

unknown, plus the quantum-mechanical nature of this particular interaction also makes the

interaction random. Single scattering is therefore often described by probability distributions.

With multiple scattering, the randomness of the interaction tends to be averaged out by

the large number of scattering events, so that the final path of the radiation appears to be a

deterministic distribution of intensity. This is exemplified by a light beam passing through thick

fog. Multiple scattering is highly analogous to diffusion, and the terms multiple scattering and

diffusion are interchangeable in many contexts. Optical elements designed to produce multiple

scattering are thus known as diffusers. Coherent backscattering, an enhancement of

backscattering that occurs when coherent radiation is multiply scattered by a random medium, is

usually attributed to weak localization.

Not all single scattering is random, however. A well-controlled laser beam can be exactly

positioned to scatter off a microscopic particle with a deterministic outcome, for instance. Such

situations are encountered in radar scattering as well, where the targets tend to be macroscopic

objects such as people or aircraft.

Similarly, multiple scattering can sometimes have somewhat random outcomes,

particularly with coherent radiation. The random fluctuations in the multiply scattered intensity

of coherent radiation are called speckles. Speckle also occurs if multiple parts of a coherent wave

scatter from different centers. In certain rare circumstances, multiple scattering may only involve



a small number of interactions such that the randomness is not completely averaged out. These

systems are considered to be some of the most difficult to model accurately.

ELECTROMAGNETIC SCATTERING

Electromagnetic waves are one of the best known and most commonly encountered forms

of radiation that undergo scattering. Scattering of light and radio waves (especially in radar) is

particularly important. Several different aspects of electromagnetic scattering are distinct enough

to have conventional names. Major forms of elastic light scattering (involving negligible energy

transfer) are Rayleigh scattering and Mie scattering. Inelastic scattering includes Brillouin

scattering, Raman scattering, inelastic X-ray scattering and Compton scattering.

Light scattering is one of the two major physical processes that contribute to the visible

appearance of most objects, the other being absorption. Surfaces described as white owe their

appearance to multiple scattering of light by internal or surface inhomogenities in the object, for

example by the boundaries of transparent microscopic crystals that make up a stone or by the

microscopic fibers in a sheet of paper. More generally, the gloss (or lustre or sheen) of the

surface is determined by scattering. Highly scattering surfaces are described as being dull or

having a matte finish, while the absence of surface scattering leads to a glossy appearance, as

with polished metal or stone.

Spectral absorption, the selective absorption of certain colours, determines the color of most

objects with some modification by elastic scattering. The apparent blue color of veins in skin is a

common example where both spectral absorption and scattering play important and complex

roles in the coloration. Light scattering can also create color without absorption, often shades of

blue, as with the sky (Rayleigh scattering), the human blue iris, and the feathers of some birds.



However, resonant light scattering in nanoparticles can produce many different highly saturated

and vibrant hues, especially when surface plasmon resonance is involved.

Models of light scattering can be divided into three domains based on a dimensionless size

parameter, α which is defined as

Where π Dp is the circumference of a particle and λ is the wavelength of incident radiation.

Based on the value of α, these domains are:

: Rayleigh scattering (small particle compared to wavelength of light)

: Mie scattering (particle about the same size as wavelength of light, valid only for

spheres)

: Geometric scattering (particle much larger than wavelength of light)

Rayleigh scattering is a process in which electromagnetic radiation (including light) is

scattered by a small spherical volume of variant refractive index, such as a particle, bubble,

droplet, or even a density fluctuation. This effect was first modelled successfully by Lord

Rayleigh, from whom it gets its name. In order for Rayleigh's model to apply, the sphere must be

much smaller in diameter than the wavelength (λ) of the scattered wave; typically the upper limit

is taken to be about 1/10 the wavelength. In this size regime, the exact shape of the scattering

center is usually not very significant and can often be treated as a sphere of equivalent volume.

The inherent scattering that radiation undergoes passing through a pure gas is due to microscopic

density fluctuations as the gas molecules move around, which are normally small enough in scale

for Rayleigh's model to apply. This scattering mechanism is the primary cause of the blue color

of the Earth's sky on a clear day, as the shorter blue wavelengths of sunlight passing overhead

are more strongly scattered than the longer red wavelengths according to Rayleigh's famous 1/λ4

relation. Along with absorption, such scattering is a major cause of the attenuation of radiation

by the atmosphere. The degree of scattering varies as a function of the ratio of the particle



diameter to the wavelength of the radiation, along with many other factors including

polarization, angle, and coherence.

For larger diameters, the problem of electromagnetic scattering by spheres was first

solved by Gustav Mie, and scattering by spheres larger than the Rayleigh range is therefore

usually known as Mie scattering. In the Mie regime, the shape of the scattering center becomes

much more significant and the theory only applies well to spheres and, with some modification,

spheroids and ellipsoids. Closed-form solutions for scattering by certain other simple shapes

exist, but no general closed-form solution is known for arbitrary shapes.

Both Mie and Rayleigh scattering are considered elastic scattering processes, in which

the energy (and thus wavelength and frequency) of the light is not substantially changed.

However, electromagnetic radiation scattered by moving scattering centers does undergo a

Doppler shift, which can be detected and used to measure the velocity of the scattering center/s

in forms of techniques such as lidar and radar. This shift involves a slight change in energy.

Fig: Rayleigh scattering and Mie scattering

At values of the ratio of particle diameter to wavelength more than about 10, the laws of

geometric optics are mostly sufficient to describe the interaction of light with the particle, and at

this point the interaction is not usually described as scattering.



For modeling of scattering in cases where the Rayleigh and Mie models do not apply such as

irregularly shaped particles, there are many numerical methods that can be used. The most

common are finite-element methods which solve Maxwell's equations to find the distribution of

the scattered electromagnetic field. Sophisticated software packages exist which allow the user to

specify the refractive index or indices of the scattering feature in space, creating a 2- or

sometimes 3-dimensional model of the structure. For relatively large and complex structures,

these models usually require substantial execution times on a computer.

INELASTIC SCATTERING

In inelastic scattering part of the kinetic energy of the incident particle is lost inside the

target giving rise to some internal processes and only a fraction of it goes into moving the whole

target. For example if you take a spherical container and then fire a small ball onto it the

collision could be considered to be elastic (in an ideal world). If you were then to fill it with

some marbles and then fire another ball at it some of the kinetic energy would go into moving

the ball, but a fraction would also move around the marbles inside. In this sense we can say that

inelastic scattering will occur if the target consists of smaller components. One other difference

between inelastic and elastic scattering is that with elastic scattering the target will not change

form, whereas with inelastic scattering the target can break up into new forms. A proton may

make hadrons (particles built from quarks) by inelastic collisions. We now see that if we can

show that the target (say a proton) scatters inelastically then we can presume that there must be

some internal process occuring, which should not happen if the particle is fundamental, because

this suggests there is something smaller inside to cause this process. This is just what happened

at SLAC with deep inelastic scattering, by probing the nucleon it was found to scatter

inelastically, just as though there were smaller particles inside.



2. RAMAN SCATTERING

When photons are scattered from an atom or molecule, most photons are elastically

scattered (Rayleigh scattering), such that the scattered photons have the same energy (frequency

and wavelength) as the incident photons. A small fraction of the scattered photons

(approximately 1 in 10 million) are scattered by an excitation, with the scattered photons having

a frequency different from, and usually lower than, that of the incident photons. In a gas, Raman

scattering can occur with a change in energy of a molecule due to a transition. Typically, in

Raman spectroscopy high intensity laser radiation with wavelengths in either the visible or near-

infrared regions of the spectrum is passed through a sample. Photons from the laser beam

produce an oscillating polarization in the molecules, exciting them to a virtual energy state. The

oscillating polarization of the molecule can couple with other possible polarizations of the

molecule, including vibrational and electronic excitations. If the polarization in the molecule

does not couple to these other possible polarization, then it will not change the vibrational state

that the molecule started in and the scattered photon will have the same energy as the original

photon. This type of scattering is known as Rayleigh scattering. When the polarization in the

molecules couples to a vibrational state that is higher in energy than the state they started in, then

the original photon and the scattered photon differ in energy by the amount required to

vibrationally excite the molecule. In perturbation theory, the Raman effect corresponds to the

absorption and subsequent emission of a photon via an intermediate quantum state of a material.

The intermediate state can be either a "real", i.e., stationary state or a virtual state.

The Raman interaction leads to two possible outcomes: 1) The material absorbs energy

and the emitted photon has a lower energy than the absorbed photon. This outcome is labelled

Stokes Raman scattering. 2) The material loses energy and the emitted photon has a higher

energy than the absorbed photon. This outcome is labelled anti-Stokes Raman scattering.

The energy difference between the absorbed and emitted photon corresponds to the

energy difference between two resonant states of the material and is independent of the absolute

energy of the photon.



The spectrum of the scattered photons is termed the Raman spectrum. It shows the

intensity of the scattered light as a function of its frequency difference Δν to the incident

photons. The locations of corresponding Stokes and anti-Stokes peaks form a symmetric pattern

around Δν=0. The frequency shifts are symmetric because they correspond to the energy

difference between the same upper and lower resonant states. The intensities of the pairs of

features will typically differ, though. They depend on the populations of the initial states of the

material, which in turn depend on the temperature. In thermodynamic equilibrium, the upper

state will be less populated than the lower state. Therefore, the rate of transitions from the lower

to the upper state (Stokes transitions) will be higher than in the opposite direction (anti-Stokes

transitions). Correspondingly, Stokes scattering peaks are stronger than anti-Stokes scattering

peaks. Their ratio depends on the temperature (which can practically be exploited for the

measurement of temperature).

Fig: Different types of light scattering

The Raman-scattering process as described above takes place spontaneously; i.e., in

random time intervals, one of the many incoming photons is scattered by the material. This

process is thus called spontaneous Raman scattering.



On the other hand, stimulated Raman scattering can take place when some Stokes

photons have previously been generated by spontaneous Raman scattering (and somehow forced

to remain in the material), or when deliberately injecting Stokes photons ("signal light") together

with the original light ("pump light"). In that case, the total Raman-scattering rate is increased

beyond that of spontaneous Raman scattering: pump photons are converted more rapidly into

additional Stokes photons. The more Stokes photons are already present, the faster more of them

are added. Effectively, this amplifies the Stokes light in the presence of the pump light, which is

exploited in Raman amplifiers and Raman lasers. Stimulated Raman scattering is a nonlinear-

optical effect. It can be described using a third-order nonlinear susceptibility.

In spontaneous Raman scattering, only one laser beam at a frequency ωp illuminates the

sample and the signal is generated at the Stokes and anti-Stokes frequencies, ωs and ωas,

respectively, due to inelastic scattering. In SRS, however, two laser beams at ωp and ωS coincide

on the sample. When the difference frequency Δω=ωp-ωS (also called the Raman shift), matches

a particular molecular vibrational frequency Ω, amplification of the Raman signal is achieved by

virtue of stimulated excitation of molecular transition rate r. r ~ σRaman· np· (nS +1) σRaman is

the (Raman-shift dependent) Raman scattering cross-section of the molecule and np and nS are

the number of photons per mode in the pump and Stokes fields, respectively. In the absence of

the Stokes-beam (nS=0), the unity in the equation above accounts for spontaneous Raman

scattering. Under our typical excitation condition nS is, however, bigger than 10^7; hence,

stimulated Raman scattering provides amplification at the vibrational transition rate. As a

consequence of the amplified energy transition rate, the intensity of the Stokes beam, IS,

experiences a gain, ΔIS, (stimulated Raman gain, SRG) and the intensity of the pump beam, Ip,

experiences a loss, ΔIp, (stimulated Raman loss, SRL). Either ΔIS or ΔIp can be used as

vibrational contrast for SRG and SRL microscopy, respectively.SRS cannot occur when Δω does

not match any vibrational resonance that absorbs the difference energy from the fields. Thus,

SRS does not have a nonresonant background signal. -point three-dimensional imaging of thick

specimens.



3. APPLICATIONS OF STIMULATED RAMAN

SCATTERING

Raman spectroscopy employs the Raman Effect for substances analysis. The spectrum of

the Raman-scattered light depends on the molecular constituents present and their state, allowing

the spectrum to be used for material identification and analysis. Raman spectroscopy is used to

analyze a wide range of materials, including gases, liquids, and solids. Highly complex materials

such as biological organisms and human tissue can also be analyzed by Raman spectroscopy.

For solid materials, Raman scattering is used as a tool to detect high-frequency phonon

and magnon excitations. Raman lidar is used in atmospheric physics to measure the atmospheric

extinction coefficient and the water vapour vertical distribution. Stimulated Raman transitions

are also widely used for manipulating a trapped ion's energy levels, and thus basis qubit states.

Raman spectroscopy can be used to determine the force constant and bond length for

molecules that do not have an infrared absorption spectrum. Raman amplification is used in

optical amplifiers.

For high-intensity continuous wave (CW) lasers, SRS can be used to produce broad

bandwidth spectra. This process can also be seen as a special case of four-wave mixing, wherein

the frequencies of the two incident photons are equal and the emitted spectra are found in two

bands separated from the incident light by the phonon energies. The initial Raman spectrum is

built up with spontaneous emission and is amplified later on. At high pumping levels in long

fibers, higher-order Raman spectra can be generated by using the Raman spectrum as a new

starting point, thereby building a chain of new spectra with decreasing amplitude. The

disadvantage of intrinsic noise due to the initial spontaneous process can be overcome by seeding

a spectrum at the beginning, or even using a feedback loop as in a resonator to stabilize the

process.



4. CHARACTERIZATION OF SRS FOR DIFFERENT

MATERIALS

Stimulated Raman scattering was first discovered by an accident, when a cell with

nitrobenzene was introduced inside a ruby laser cavity. On the output, Woodbury and Ng

observed a rather strong emission at the wavelength other than the fundamental wavelength of

ruby laser, 694.3 nm. While initial explanation suggested the presence of some sort of

fluorescence/luminescence emission, later it was realized that it is a two-photon process, which

can be fully described by quantum mechanical calculations. Later, Garmier and Bloembergen

and Shen introduced the coupled-wave formalism to describe the stimulated Raman effect. The

very first experimental observation of stimulated Raman scattering (SRS) has clearly

demonstrated the great potential of this technique (i) to generate new colors of light and (ii) to

dramatically enhance the efficiency of weak Raman transition.

Stimulated Raman scattering (SRS) has been well investigated in a variety of materials. It

offers a simple and inexpensive way of tuning the wavelength of a laser system. The stimulated

Raman process originates from spontaneous Raman scattering and requires high pump

intensities, reducing the conversion efficiency of the process. Further, at sufficiently high

intensities, other non-linear optical effects such as stimulated Brillouin scattering start appearing.

In ultra-short pulse interactions, SRS has to compete with continuum generation. Methods such

as external seeding, either by way of injection of radiation into the Raman medium at a Stokes

shifted wavelength, or by addition of lasing dye particularly for liquids that fluoresce at the

Raman lines of the medium are used to reduce the threshold of stimulated Raman process. The

addition of lasing dye into a neat solvent leads to interesting competition between SRS from the

solvent and amplified spontaneous emission (ASE) from the dye, provided there is spectral

overlap between the two processes. Under such conditions, SRS, fluorescence and ASE cannot



be treated independently and SRS builds up mostly from the dye fluorescence. In addition, if

there is sufficient stimulated emission from the dye, the Raman gain can be boosted

substantially. Another important feature of SRS is the shortening of the Stokes pulse width from

that of the input laser pulse. Pulse compression factors as high as 40 have been observed in

backward SRS. Such a large compression is possible due to the fact that backscattered pulse

continuously encounters an undepleted pump light giving rise to high amplification and

sharpening. On the other hand a forward traveling Stokes pulse has access only to the pump

energy stored in the traveling volume region occupied. In addition, saturation due to pump

depletion limits the forward Stokes emission. However, Forward SRS has some intrinsic

advantages over its backward counterpart in terms of simplicity of set up, ease of design of the

optics, separation from pump beam etc. There is, therefore, a pressing need to find methods that

can enhance forward SRS. The addition of a dye whose fluorescence acts as a seed for SRS is

one such option. The availability of population inversion in the dye can further enhance the

forward Raman gain dramatically. Intense SRS, though in the backward geometry, has been

reported using highly fluorescent dyes such as Rhodamine-6G and DCM. Recently, one of the

authors has reported highly efficient mirrorless lasing using single and multi-photon absorption

in weakly fluorescent stibazolium salt styryl pyridinium cyanine dye (SPCD) or 4¢-

dimethylamino-N-methyl-4-stilbazolium methylsulfate (DMSM) [13,14]. These belong to a new

class of molecules that are weak in florescence but surprisingly have ASE. The high ASE

efficiency (40%) has been attributed to large dipole moments associated with the charge transfer

transition in the organic molecular salts. It is therefore interesting to explore if the strong ASE

from these molecules can enhance SRS (particularly the forward process) efficiencies.

In this paper we investigate backward SRS of Acetone, Methanol, Xylene, Methyl

Acetate and Demineralised Water. We examine the changes of SRS when a dye (RHODAMINE

6G, Rhodamine B, Methylene Blue) added to this solvent. We also examine the spectral

evolution of the backward Raman emission at various pump intensities.



5. RESEARCH MATERIALS

ACETONE

Acetone is a colourless and highly flammable manufactured liquid. It has a distinctive

fruity or mint-like odor and a pungent taste. It is also found naturally in plants, trees, volcanic

gases, and forest fires, and as a by-product of the breakdown of body fat. It is found in vehicle

exhaust, tobacco smoke, and landfill sites. The chemical formula for acetone is C3H6O. Acetone

is used as a solvent to dissolve other substances, such as paints, varnishes, lacquers, fats, oils,

waxes, resins, printing inks, plastics, and glues. It is used to make plastics, fibres, drugs, rayon,

photographic film, smokeless powder, and other chemicals. It is also used for cleaning and

drying precision parts. Household and consumer products that contain acetone include fingernail

polish remover, particle board, paint remover, liquid or paste waxes and polishes, detergent,

cleaning products, and rubber cement. Acetone is produced and disposed of in the human body

through normal metabolic processes. It is normally present in blood and urine. People with

diabetes produce it in larger amounts. Reproductive toxicity tests show that it has low potential

to cause reproductive problems. Pregnant women, nursing mothers and children have higher

levels of acetone. Ketogenic diets that increase acetone in the body are used to reduce epileptic

attacks in infants and children who suffer from recalcitrant refractory epilepsy.



Fig: Structure of Acetone

Acetone is produced directly or indirectly from propylene. Approximately 83% of

acetone is produced via the cumene process; as a result, acetone production is tied to phenol

production. In the cumene process, benzene is alkylated with propylene to produce cumene,

which is oxidized by air to produce phenol and acetone. Other processes involve the direct

oxidation of propylene (Wacker-Hoechst process), or the hydration of propylene to give 2-

propanol, which is oxidized to acetone.

METHANOL

Methanol, also known as methyl alcohol, is a chemical with the formula CH3OH(often

abbreviated MeOH). Methanol acquired the name "wood alcohol" because it was once produced

chiefly as a by-product of the destructive of wood. Modern-day methanol production occurs in a

catalytic industrial process directly from carbon monoxide, carbon dioxide, and hydrogen.

Methanol is the simplest alcohol, and is a light, volatile, colorless, flammable liquid with a

distinctive odor very similar to that of ethanol (drinking alcohol). However, unlike ethanol,

methanol is highly toxic and unfit for consumption. At room temperature, it is a polar, and is

used as an antifreeze, solvent, fuel, and as a denaturant for ethanol. It is also used for

producing biodiesel via transesterification reaction.



Methanol is produced naturally in the anaerobic metabolism of many varieties of bacteria, and is

commonly present in small amounts in the environment. As a result, there is a small fraction of

methanol vapour in the atmosphere. Over the course of several days, atmospheric methanol

is oxidized with the help of sunlight to carbon dioxide and water. Methanol also forms in

abundant quantities in star forming regions of space, and is used in astronomy as a marker for

such regions. It is detected through its spectral emission lines.

Methanol burns in oxygen, including open air, forming carbon dioxide and water:

2 CH3OH + 3 O2 → 2 CO2 + 4 H2O

Methanol ingested in large quantities is metabolized to formic acid or formate salts, which is

poisonous to the central nervous system, and may cause blindness, coma, and death. Because of

these toxic properties, methanol is frequently used as a denaturant additive for ethanol

manufactured for industrial uses. This addition of methanol exempts industrial ethanol

(commonly known as "denatured alcohol" or "methylated spirit") from liquor excise taxation in

the US and some other countries.

Fig: Structure of Methanol



XYLENE

Xylene dimethyl benzene is a hydrocarbon mixture consisting of a benzene ring with

two methyl groups at various substituted positions. The three isomers of xylene have

the molecular formula C8H10, also represented by the semi-structural formula C6H4 (CH3)2.

Xylene is a major petrochemical produced by catalytic reforming and also by coal

carbonization in the manufacture of coke fuel. It represents about 0.5–1% of crude oil

(depending on the source), and is found in small quantities in gasoline and aircraft fuels. Xylenes

are mainly produced as part of the BTX aromatics (benzene, toluene and xylenes) extracted from

the product of catalytic reforming known as "reformate". The mixture is a slightly greasy,

colorless liquid commonly encountered as a solvent. Xylene was named in 1851, having been

discovered as a constituent of wood. Several million tons are produced annually. In 2011, a

global consortium began construction of one of the world’s largest xylene plants in Singapore.

Fig: Structure of Xylene



METHYL ACETATE

Methyl acetate, also known as acetic acid methyl ester or methyl ethanoate, is a

carboxylate ester with the formula CH3COOCH3. It is a flammable liquid with a

characteristically pleasant smell reminiscent of some glues and nail polish removers. Methyl

acetate is occasionally used as a solvent, being weakly polar and lipophilic, but its close

relative ethyl acetate is a more common solvent being less toxic and less soluble in water.

Methyl acetate has a solubility of 25% in water at room temperature. At elevated temperature its

solubility in water is much higher. Methyl acetate is not stable in the presence of strong

aqueous bases or aqueous acids. Methyl acetate is not considered as a VOC.

Fig: Structure of Methyl Acetate

DEMINERALISED WATER

Demineralised Water is water of an extremely high quality. It is produced by means of a physical

process, needs a specialist piece of equipment to produce it called a demineralisation plant or a

deionisation plant.The incoming water passes over a series of ‘resin beds’ which remove mineral

ions and other impurities from the water. This is why Demineralised Water is also known as

Deionised Water; the process removes minerals and ions leaving water which is de-mineralised

or de-ionised. Demineralised Water is also known as Demin Water, DI Water and DIW.



Demineralised water is water completely free (or almost) of dissolved minerals as a result of one

of the following processes:

distillation

deionization

membrane filtration (reverse osmosis or nanofiltration)

electrodyalisis

Or other technologies.

The amount of dissolved solids in water that has followed one of these processes could be as low

as 1 mg/l and is in any case always less than 10 mg/l. The electrical conductivity is generally less

than 2 mS/m and may be even lower (< 0,1 mS/cm).

RHODAMINE 6G

Rhodamine 6G is a highly fluorescent Rhodamine family dye. It is often used as a tracer

dye within water to determine the rate and direction of flow and transport. Rhodamine dyes

fluoresce and can thus be detected easily and inexpensively with instruments called fluorometers.

Rhodamine 6G is also used as a laser dye, or gain medium, in dye lasers, and is pumped by the

2nd (532 nm) harmonic from an Nd:YAG laser or nitrogen laser. The dye has a remarkably high

photo stability, high fluorescence quantum yield (0.95), low cost, and its lasing range has close

proximity to its absorption maximum (approximately 530 nm). The lasing range of the dye is 555

to 585 nm with a maximum at 566 nm. Rhodamine 6G usually comes in three different forms.



Rhodamine 6G chloride is a bronze/red powder with the chemical formula C27H29ClN2O3.

Although highly soluble, this formulation is very corrosive to all metals except stainless steel.

Other formulations are less soluble, but also less corrosive. Rhodamine 6G perchlorate

(C27H29ClN2O7) comes in the form of red crystals, while rhodamine 6G tetrafluoroborate

(C27H29BF4N2O3) appears as maroon crystals.

Fig: Structure of Rhodamine 6G

RHODAMINE B

Rhodamine B is a chemical compound and a dye. It is often used as a tracer dye within water to

determine the rate and direction of flow and transport. Rhodamine dyes fluoresce and can thus be

detected easily and inexpensively with instruments called fluorometers. Rhodamine dyes are

used extensively in biotechnology applications such as fluorescence microscopy, flow

cytometry, fluorescence correlation spectroscopy and ELISA.



Rhodamine B is tunable around 610 nm when used as a laser dye. Its luminescence quantum

yield is 0.65 in basic ethanol, 0.49 in ethanol 1.0 and 0.68 in 94% ethanol. The fluorescence

yield is temperature dependent. The solubility of Rhodamine B in water is ~15 g/L. However, the

solubility in acetic acid solution (30 vol.%) is ~400 g/L. Chlorinated tap water decomposes

rhodamine B. Rhodamine B solutions adsorb to plastics and should be kept in glass.

Fig: Structure of Rhodamine B

METHYLENE BLUE

Methylene blue (CI 52015) is a heterocyclic aromatic chemical compound with the molecular

formula C16H18N3SCl. It has many uses in a range of different fields, such

as biology and chemistry. At room temperature it appears as a solid, odorless, dark green



powder, that yields a blue solution when dissolved in water. The hydrated form has 3 molecules

of water per molecule of methylene blue. Methylene blue should not be confused with methyl

blue, another histology stain, new methylene blue, nor with the methyl violets often used as Ph

indicators.

Methylene blue was first prepared in 1876 by German chemist Heinrich Caro (1834-1910). It is

on the World Health Organization's List of Essential Medicines, a list of the most important

medication needed in a basic health system. Methylene blue is a potent cationic dye with

maximum absorption of light around 670 nm. The specifics of absorption depend on a number of

factors, including protonation, adsorption to other materials, and metachromasy - the formation

of dimers and higher-order aggregates depending on concentration and other interactions

Fig: Structure of Methylene Blue



6. EXPERIMENT SET UP

The experiment setup is shown in fig:

Fig: Experiment Setup

Laser

We were used Spectra- Physics Quanta-Ray high-pulse energy Nd: YAG laser with a

power of 1 joule for 1064 nano meter at 10 Hz. For 532 nano meter it have energies 500 milli

joule, 400 milli joule, 250 milli joule and 120 milli joule for 10Hz,30 Hz, 50Hz, 100Hz

respectively. Spectra-Physics® Quanta-Ray® high-pulse energy Nd:YAG lasers are recognized



Worldwide for their unsurpassed performance, reliability and quality. They incorporate

pioneering technologies such as dual-rod oscillators, gold-coated elliptical pump chambers,

internal sealed beam paths, and high-damage-threshold optics from Spectra-Physics’ advanced

coatings lab—all combine to create the best beam quality and highest energies in the industry.

The heart of the Quanta-Ray laser is its unique pump chamber. The chamber strikes the

perfect balance between efficiency and beam mode quality by employing elliptical goldcoated

reflectors to couple the lamps into the Nd:YAG rod. The gold surfaces provide high reflectivity

at pump wavelengths while attenuating UV wavelengths. Proprietary diffusion techniques ensure

uniform illumination of the Nd:YAG rod Quanta-Ray lasers are also the only lasers on the

market to feature completely sealed internal beam paths through the use of nitrogen-purged beam

tubes.

Sealed beam paths greatly extend the longevity of optical coatings by shielding all optical

components from harmful contaminants in even the harshest of environments Sol-Gel coated

pockels cells coating greatly enhances the lifetime of the cells and improves the performance of

the laser system. BBO FHGs give highest energies, best beam quality and highest damage

thresholds.

Lens

We have used a lens with a focal length of 10 cm. It is helping us to focus the laser beam into the

middle of the cell.

Cell

We have used a cell with 10 centi meter length and 4 cm diameter. The length of the cell makes

more interaction length between acetone and laser beam. It is helped us to get better SBS and

SRS.



BEAM SPLITTER

A beam splitter is an optical device that splits a beam of light in two. It is the crucial part

of most interferometers.

In its most common form, a cube, it is made from two triangular glass prisms which are

glued together at their base using polyester, epoxy, or urethane-based adhesives. The thickness of

the resin layer is adjusted such that (for a certain wavelength) half of the light incident through

one "port" (i.e., face of the cube) is reflected and the other half is transmitted due to frustrated

total internal reflection. Polarizing beam splitters, such as the Wollaston prism,

use birefringent materials, splitting light into beams of differing polarization.

Another design is the use of a half-silvered mirror, a sheet of glass or plastic with a

transparently thin coating of metal, now usually aluminium deposited from aluminium vapor.

The thickness of the deposit is controlled so that part (typically half) of the light which is

incident at a 45-degree angle and not absorbed by the coating is transmitted, and the remainder is

reflected. A very thin half-silvered mirror used in photography is often called a pellicle mirror.

To reduce loss of light due to absorption by the reflective coating, so-called "swiss cheese" beam

splitter mirrors have been used. Originally, these were sheets of highly polished metal perforated

with holes to obtain the desired ratio of reflection to transmission. Later, metal was sputtered



On to glass so as to form a discontinuous coating, or small areas of a continuous coating were

removed by chemical or mechanical action to produce a very literally "half-silvered" surface.

Instead of a metallic coating, a dichroic optical coating may be used. Depending on its

characteristics, the ratio of reflection to transmission will vary as a function of the wavelength of

the incident light. Dichroic mirrors are used in some ellipsoidal reflector spotlights to split off

unwanted infrared (heat) radiation, and as output couplers in laser construction.

A third version of the beam splitter is a dichroic mirrored prism assembly which

uses dichroic optical to divide an incoming light beam into a number of spectrally distinct output

beams. Such a device was used in three-pickup-tube color television cameras and the three-

strip Technicolor movie camera. It is currently used in modern three-CCD cameras. An Optically

similar system is used in reverse as a beam-combiner in three-LCD projectors, in which light

from three separate monochrome LCD displays is combined into a single full-color image for

projection.

In our experiment the beam splitter is used to split the backward stimulated brillouin

scattering. One part is going to the detector and the other part is return to the filter. The beam

filter is kept in such a way that it will make 450 to the plane of laser beam.

OCEAN OPTICS HR4000

The spectrometer used is the ocean optics HR4000 High-Resolution Miniature Fiber Optic

Spectrometer. The HR4000 High-Resolution Miniature Fiber Optic Spectrometer provides

optical resolution as good as 0.025 nm (FWHM). The HR4000 is responsive from 200-1100 nm,

but the specific range and resolution depends on your grating and entrance slit selections.

The HR4000 is perfect for applications where high resolution is necessary, such as absorbance

of gases or atomic emission lines (for solution chemistry or for color measurements, the USB4000

is more appropriate).

Data programmed into a memory chip on each HR4000 includes wavelength calibration

coefficients, linearity coefficients, and the serial number unique to each spectrometer. Our



spectrometer operating software simply reads these values from the spectrometer — a feature that

enables hot swapping of spectrometers among computers.

Fig: Ocean Optics HR4000 High-Resolution Fiber Optic Spectrometer

The HR4000 Spectrometer connects to a notebook or desktop computer via USB port or serial

port. When connected to the USB port of a computer, the HR4000 draws power from the host

computer, eliminating the need for an external power supply.

SPECIFICATIONS

Fig: HR4000 Spectrometer with Components



Item Name Description

1 SMA Connector

Secures the input fiber to the spectrometer. Light from the input fiber enters the optical bench through this connector.

2 Slit

A dark piece of material containing a rectangular aperture, which is mounted directly behind the SMA Connector. The size of the aperture regulates the amount of light that enters the optical bench and controls spectral resolution.

You can also use the HR4000 without a Slit. In this configuration, the diameter of the fiber connected to the HR4000 determines the size of the entrance aperture.

Only Ocean Optics technicians can change the Slit.

3 Filter

Restricts optical radiation to pre-determined wavelength regions. Light passes through the Filter before entering the optical bench. Both bandpass and longpass filters are available to restrict radiation to certain wavelength regions.

Only Ocean Optics technicians can change the Filter.

4 Collimating Mirror Focuses light entering the optical bench towards the



Grating of the spectrometer.

Light enters the spectrometer, passes through the SMA Connector, Slit, and Filter, and then reflects off the Collimating Mirror onto the Grating.

5 Grating

Diffracts light from the Collimating Mirror and directs the diffracted light onto the Focusing Mirror. Gratings are available in different groove densities, allowing you to specify wavelength coverage and resolution in the spectrometer.

Only Ocean Optics technicians can change the Grating.

6 Focusing Mirror

Receives light reflected from the Grating and focuses the light onto the CCD Detector or L2 Detector Collection Lens (depending on the spectrometer configuration).

7 L2 Detector Collection Lens

An optional component that attaches to the CCD Detector. It focuses light from a tall slit onto the shorter CCD Detector elements.

The L2 Detector Collection Lens should be used with large diameter slits or in applications with low light levels. It also improves efficiency by reducing the



effects of stray light.

Only Ocean Optics technicians can add or remove the L2 Detection Collection Lens.

8 CCD Detector (UV or VIS)

Collects the light received from the Focusing Mirror and converts the optical signal to a digital signal.

CCD Detector Specifications Specification

Value

Detector Toshiba TCD1304AP linear CCD array

No. of elements 3648 pixels

Sensitivity 100 photons per count at 800 nm

Pixel size 8 μm x 200 μm

Pixel well depth -100,000 electrons

Signal-to-noise ratio 300:1 (at full signal)

A/D resolution 14 bit

Dark noise 8 RMS counts

Corrected linearity >99.8%

Maximum pixel rate Rate at which pixels are digitized is 1 MHz

Stray light <0.05% at 600 nm; <0.10% at 435 nm

Dynamic range 2 x 109 (system); 2000:1 for a single acquisition

Fiber optic connector SMA 905 to single-strand optical fiber (0.22 NA)

Data transfer rate Full scans into memory every 4 milliseconds with USB 2.0 port, every 600 milliseconds with the serial port



Integration time 3.8 ms to 10 seconds

Interfaces USB 2.0, 480 Mbps (USB 1.1 compatible); RS-232 (2-wire); SPI (3-wire); I2C Inter-Integrated Circuit 2-wire serial bus

Operating systems

Windows 98/Me/2000/XP, Mac OS X, and Linux when using the USB port Any 32-bit Windows operating system when using the serial port

Onboard GPIO 10 user-programmable digital I/Os

Analog channels One 13-bit analog input and one 9-bit analog output

HR4000 Spectrometer Specification Value

Dimensions 148.6 mm x 104.8 mm x 45.1 mm

Weight 570 g

Power consumption 450 mA @ 5 VDC

Detector 3648-element linear silicon CCD array

Detector range 200-1100 nm

Gratings 14 gratings available

Specification Value Entrance aperture 5, 10, 25, 50, 100 or 200 μm wide slits

Order-sorting filters Installed longpass and bandpass filters

Focal length f/4, 101 mm

Optical resolution Depends on grating and size of entrance aperture

Stray light <0.05% at 600 nm; <0.10% at 435 nm

Dynamic range 2 x 109 (system); 2000:1 for a single acquisition

Fiber optic connector SMA 905 to single-strand optical fiber (0.22 NA)



Data transfer rate Full scans into memory every 4 milliseconds with USB 2.0 port, every 600 milliseconds with the serial port

Integration time 3.8 ms to 10 seconds

Interfaces USB 2.0, 480 Mbps (USB 1.1 compatible); RS-232 (2-wire); SPI (3-wire); I2C Inter-Integrated Circuit 2-wire serial bus

Operating systems

Windows 98/Me/2000/XP, Mac OS X, and Linux when using the USB port Any 32-bit Windows operating system when using the serial port

Onboard GPIO 10 user-programmable digital I/Os

Analog channels One 13-bit analog input and one 9-bit analog output

OCEAN OPTICS SOFTWARE – SPECTRASUITE

SpectraSuite is the latest generation of operating software for all Ocean Optics spectrometers.

It is a completely modular, Java-based spectroscopy software platform that operates on Windows,

Macintosh and Linux operating systems. The software can control any Ocean Optics USB

spectrometer and device, as well as any other manufacturer’s USB instrumentation using the

appropriate drivers.

SpectraSuite is a user-customizable, advanced acquisition and display program that provides a

real-time interface to a variety of signal-processing functions. With SpectraSuite, you have the

ability to perform spectroscopic measurements (such as absorbance, reflectance, and emission),

control all system parameters, collect and display data in real time, and perform reference

monitoring and time acquisition experiments.



FILTERS

1064 nano meter filter has a centre wavelength of 1064 ± 2 nano meter, and full width

half max of 10 ± 2 nano meter. It is optimized to block X-ray to 1200 nano meter wavelengths.

Laser Line Filters are ideal for transmitting laser light while suppressing ambient light.

532 nano meter filter has a centre wavelength of 532 ± 2 nano meter, and full width half

max of 10 ± 2 nano meter. It is optimized to block X-ray to Far IR wavelengths. Laser Line

Filters are ideal for transmitting laser light while suppressing ambient light

Fig: Experiment set up



7. OBSERVATIONS

By irradiating the cell containing 100ml sample using 1 joule Nd-YAG laser and detected the

backward stimulated scattering using ocean optics. The peak amplitude and corresponding

wavelength at different laser power levels is given below

STIMULATED RAMAN SCATTERING FROM ACETONE

Pure

SL.No POWER(mW) AMPLITUDE WAVELENGTH (nm)

1 68 1363 629.6

2 195 3512 629.6

3 419 11088 629.6

4 658 11920 629.6

5 890 15535 629.6

6 1000 16333 629.6

In a molar solution of pure acetone, Stimulated Raman scattering starting at a threshold laser power of 68 mW. At 1000 mW laser power Stimulated Raman scattering occurring at a wavelength of 629.6 nano meter with a peak amplitude of 16333 Arb.unit.



The power versus amplitude graph for a molar solution of pure Acetone is given below



RHODAMINE6G IN ACETONE

Concentration 10-5 molar


1 195 1358 629.34

2 419 1358 629.34

3 658 2202 629.34

4 890 5728 629.6

5 1000 8360 629.6

In 10-5 molar solution of Rhodamine 6G in acetone, Stimulated Raman scattering starting at a threshold laser power of 195 mW. At 1000 mW laser power Stimulated Raman scattering occurring at a wavelength of 629.6 nano meter with a peak amplitude of 8360 Arb.unit.

The power versus amplitude graph for 10-5 molar solution of rhodamine 6G in acetone is given

below





1 195 981 629.6

2 419 2113 629.34

3 658 2355 629.34

4 890 2389 629.34

5 1000 4713 629.34



In 10-6 molar solution of Rhodamine 6G in acetone, Stimulated Raman scattering starting at a threshold laser power of 195 mW. At 1000 mW laser power Stimulated Raman scattering occurring at a wavelength of 629.34 nano meter with a peak amplitude of 4713 Arb.unit.

The power versus amplitude graph for 10-6 molar solution of rhodamine 6G in acetone is given

below



RHODAMINE B IN ACETONE

Concentration -10-5 molar

SL.No POWER (mW) AMPLITUDE WAVELENGTH (nm)

1 525 1318 629.82,629.08

2 658 1558 629.82,629.08

3 890 5035 629.82

4 1000 5035 629.82,629.08

In 10-5 molar solution of Rhodamine in acetone, Stimulated Raman scattering starting at a threshold laser power of 525 mW. At 1000 mW laser power Stimulated Raman scattering occurring at a wavelength of 629.682nano meter with a peak amplitude of 5035.

The power versus amplitude graph for 10-5 molar solution of rhodamineB in acetone is given

below





1 112 2508 629.82,629.08

2 195 4541 629.82

3 419 6086 629.82,629.08

4 658 10592 629.82

5 890 22895 629.82,629.08

6 1000 30155 629.82

In 10-6 molar solution of Rhodamine B in acetone, Stimulated Raman scattering starting at a threshold laser power of 112 mW. At 1000 mW laser power Stimulated Raman scattering occurring at a wavelength of 629.682nano meter with a peak amplitude of 30155 Arb.unit.

The power versus amplitude graph for 10-6 molar solution of rhodamineB in acetone is given

below





1 95 4455 629.08

2 195 3228 629.82,629.08

3 419 4407 629.82,629.08

4 658 10081 629.82,629.08

5 890 32520 629.82,629.08

6 1000 26400 629.82,629.08

In 10-7 molar solution of Rhodamine B in acetone, Stimulated Raman scattering starting at a

threshold laser power of 95 mW. At 890 mW laser power Stimulated Raman scattering occurring

at a wavelength of 629.682nano meter with a peak amplitude of 32250 Arb.unit. The power

versus amplitude graph for 10-7 molar solution of rhodamineB in acetone is given below



METHYLENE BLUE IN ACETONE



1 313 948 629.34

2 419 1152 629.34

3 658 2666 629.34

4 890 3571 629.34

5 1000 4069 629.34

In 10-5 molar solution of methylene blue in acetone, Stimulated Raman scattering starting at a threshold laser power of 313 mW. At 1000 mW laser power Stimulated Raman scattering occurring at a wavelength of 629.34 nano meter with a peak amplitude of 4069 Arb.unit.

The power versus amplitude graph for 10-5 molar solution of methylene blue in acetone is given below





1 313 1236 629.34

2 419 2540 629.34

3 658 2542 629.08

4 890 3335 629.08

5 1000 5496 629.34

In 10-6 molar solution of methylene blue in acetone, Stimulated Raman scattering starting at a threshold laser power of 313 mW. At 1000 mW laser power Stimulated Raman scattering occurring at a wavelength of 629.34 nano meter with a peak amplitude of 5496 Arb.unit.






1 195 1171 629.08

2 419 1550 629.08

3 658 3788 629.08

4 890 4712 629.08

5 1000 5224 629.08

In 10-7 molar solution of methylene blue acetone, Stimulated Raman scattering starting at a threshold laser power of 195 mW. At 1000 mW laser power Stimulated Raman scattering occurring at a wavelength of 629.08 nano meter with a peak amplitude of 5224 Arb.unit.




RHODAMINE 6G IN 0.5 MOLAR ACETONE



1 148 1939 629.34

2 195 3538 629.34

3 419 3426 629.34

4 658 12624 629.34

5 890 54887 629.34

6 1000 70993 629.34

In 10-5 molar solution of Rhodamine 6G in 0.5 molar acetone, Stimulated Raman scattering starting at a threshold laser power of 148 mW. At 1000 mW laser power Stimulated Raman scattering occurring at a wavelength of 629.34 nano meter with a peak amplitude of 70993 Arb.unit.

The power versus amplitude graph for 10-5 molar solution of rhodamine 6G in 0.5 molar acetone is given below





1 47 2348 629.34

2 68 2868 629.34

3 195 9225 629.34

4 419 13880 629.34

5 658 39312 629.34

6 890 116380 629.34

7 1000 145338 629.34

In 10-6 molar solution of Rhodamine 6G in 0.5 molar acetone, Stimulated Raman scattering starting at a threshold laser power of 47mW. At 1000 mW laser power Stimulated Raman scattering occurring at a wavelength of 629.34 nano meter with a peak amplitude of 145338 Arb.unit.

The power versus amplitude graph for 10-6 molar solution of rhodamine 6G in 0.5 molar acetone

is given below





1 68 1585 629.34

2 195 3233 629.34

3 419 12334 629.34

4 658 20508 629.34







1 68 2195 629.34

2 195 7769 629.34

3 419 32264 629.34

4 658 72535 629.34

5 890 111454 629.34

6 1000 113992 629.34





STIMULATED RAMAN SCATTERING FROM METHANOL

Pure


1 112 1376 625.72

2 195 1910 625.72

3 419 2747 625.72

4 658 2739 625.72

5 890 3185 625.72

6 1000 6808 625.72

In a molar solution of methanol, Stimulated Raman scattering starting at a threshold laser power of 112 mW. At 1000 mW laser power Stimulated Raman scattering occurring at a wavelength of 625.72 nano meter with a peak amplitude of 6808 Arb.unit.

The power versus amplitude graph for a molar solution of methanol is given below



RHODAMINE 6G IN METHANOL



1 313 1980 625.72

2 419 5338 625.72

In a 10-5 molar solution of Rhodamine 6G in methanol, Stimulated Raman scattering starting at a threshold laser power of 113 mW. At 419 mW laser power Stimulated Raman scattering occurring at a wavelength of 625.72 nano meter with a peak amplitude of 5338 Arb.unit.

The power versus amplitude graph for a 10 -5 molar solution of rhodamine 6G methanol is given below




SL.No POWER AMPLITUDE WAVELENGTH (nm)

1 195 1417 625.72

2 419 2870 625.72

3 658 2627 625.72

4 890 5365 625.72

5 1000 7305 625.72


The power versus amplitude graph for a 10 -6 molar solution of rhodamine 6G in methanol is given below





1 195 1325 625.72

2 419 1421 625.72

3 658 1983 625.72

4 890 4282 625.72

5 1000 3378 625.72







1 419 3110 625.72

2 658 6466 625.72

3 890 4874 625.72

4 1000 3769 625.72





RHODAMINE B IN METHANOL



1 365 1778 625.46

2 419 2183 625.46

3 658 2534 625.46

4 890 4929 625.46

5 1000 6726 625.46

In a 10-6 molar solution of Rhodamine B in methanol, Stimulated Raman scattering starting at a threshold laser power of 365 mW. At 1000 mW laser power Stimulated Raman scattering occurring at a wavelength of 625.46 nano meter with a peak amplitude of 6726 Arb.unit.

The power versus amplitude graph for a 10 -6 molar solution of rhodamine B in methanol is given below





1 365 1330 625.46

2 419 2214 625.46

3 658 2116 625.46

4 890 4929 625.46

5 1000 6876 625.46

In a 10-7 molar solution of Rhodamine B in methanol, Stimulated Raman scattering starting at a threshold laser power of 365 mW. At 1000 mW laser power Stimulated Raman scattering occurring at a wavelength of 625.46 nano meter with a peak amplitude of 6876 Arb.unit.

The power versus amplitude graph for a 10 -7 molar solution of rhodamine B in methanol is given below



METHYLENE BLUE IN METHANOL



1 365 1469 625.46

2 419 1381 625.46

3 658 2005 625.46

4 890 2373 625.46

5 1000 2388 625.46

In a 10-6 molar solution of methylene blue in methanol, Stimulated Raman scattering starting at a threshold laser power of 365 mW. At 1000 mW laser power Stimulated Raman scattering occurring at a wavelength of 625.46 nano meter with a peak amplitude of 2388 Arb.unit.

The power versus amplitude graph for a 10 -6 molar solution of methylene blue in methanol is given below





1 365 1019 625.2

2 419 2193 625.2

3 658 1785 625.2

4 890 2356 625.2

5 1000 3506 625.2

In a 10-7 molar solution of methylene blue in methanol, Stimulated Raman scattering starting at a threshold laser power of 365 mW. At 1000 mW laser power Stimulated Raman scattering occurring at a wavelength of 625.2 nano meter with a peak amplitude of 3506 Arb.unit.

The power versus amplitude graph for a 10-7 molar solution of methylene blue in methanol is given below



STIMULATED RAMAN SCATTERING FROM

METHYL ACETATE

Pure


1 18 1331 629.86

2 68 2684 629.86

3 195 3304 629.86

4 419 11843 629.86

5 658 14587 629.86

6 890 13653 629.86

7 1000 12567 629.86

In a molar solution of pure methyl acetate, Stimulated Raman scattering starting at a threshold laser power of 18 mW. At 658 mW laser power Stimulated Raman scattering occurring at a wavelength of 629.86 nano meter with a peak amplitude of 14587 Arb.unit.

The power versus amplitude graph for a molar solution of pure methyl acetate is given below



RHODAMINE 6G IN METHYL ACETATE



1 47 1034 629.86

2 68 1559 629.86

3 195 1897 629.86

4 419 3902 629.86

5 658 5164 629.86

6 890 7505 629.86

7 1000 6401 629.86

In a 10-5 molar solution of Rhodamine 6G in methyl acetate, Stimulated Raman scattering starting at a threshold laser power of 47 mW. At 890 mW laser power Stimulated Raman scattering occurring at a wavelength of 629.86 nano meter with a peak amplitude of 7505 Arb.unit.

The power versus amplitude graph for a 10 5 molar solution of rhodamine 6G in methyl acetate is given below





1 32 1149 629.86

2 68 1710 629.86

3 195 4753 629.86

4 419 10046 629.86

5 658 14095 629.86

6 890 16793 629.86

7 1000 19313 629.86

In a 10-6 molar solution of Rhodamine 6G in methyl acetate, Stimulated Raman scattering starting at a threshold laser power of 32 mW. At 890 mW laser power Stimulated Raman scattering occurring at a wavelength of 629.86 nano meter with a peak amplitude of 19313 Arb.unit.

The power versus amplitude graph for a 10 6 molar solution of rhodamine 6G in methyl acetate is given below



RHODAMINE B IN METHYL ACETATE



1 47 2206 629.86

2 68 2067 629.86

3 195 3145 629.86

4 419 5189 629.86

5 658 5679 629.86

6 890 6078 629.86

7 1000 6294 629.86

In a 10-5 molar solution of Rhodamine B in methyl acetate, Stimulated Raman scattering starting at a threshold laser power of 47 mW. At 1000 mW laser power Stimulated Raman scattering occurring at a wavelength of 629.86 nano meter with a peak amplitude of 6294 Arb.unit.

The power versus amplitude graph for a 10-5 molar solution of rhodamine B in methyl acetate is given below





1 32 1708 629.86

2 68 4170 629.86

3 195 7737 629.86

4 419 17815 629.86

5 658 21755 629.86

6 890 24930 629.86

7 1000 25860 629.86







1 18 1279 629.86

2 32 2757 629.86

3 68 3775 629.86

4 195 7047 629.86

5 419 11465 629.86

6 658 20688 629.86

7 890 19325 629.86

8 1000 22118 629.86





STIMULATED RAMAN SCATTERING FROM XYLENE

Stimulated Raman scattering from xylene is studied. But no SRS obtained from this solution.

STIMULATED RAMAN SCATTERING FROM

DEMINERALISED WATER

Stimulated Raman scattering from demineralized water is studied. SRS obtained from this

solution at highest laser power level (1000mw), but it is not able to detect using ocean optics.



8. RESULT AND ANALYSIS

Studied the Backward SRS of Acetone, Methanol, Xylene, Methyl Acetate and Demineralised

Water. Changes of SRS when a dye (RHODAMINE 6G, Rhodamine B, Methylene Blue) added

to this solvent are also examined. Examined the spectral evolution of the backward Raman

emission at various pump intensities.

ACETONE

From observations, it is seen that the amplitude of the stimulated Raman scattering emissions

from pure acetone increases with incident power. As the incident power increases, the scattered

molecules get more energy. Then the amplitude of the emission increases with power. The

stimulated Raman scattering from acetone does not follow the specific characteristics. The

Raman emissions from acetone can be improved by adding some specific dyes such as

Rhodamine 6G, Rhodamine B, and Methylene Blue to the solution.

When we add Rhodamine 6G to the acetone, it is seen that, the stimulated Raman scattering does

not occur at the higher concentrations. At the higher concentrations, the incident photons are

absorbed by the medium and no scattering takes place. We got SRS emissions from 10-5 molar

concentration onwards. The SRS emissions from this medium follow a specific characteristics.

As the concentration decreases, the amplitude of the Raman emission also decreases.

From observations it is observed that, when we add Rhodamine B to the acetone, the stimulated

Raman scattering does not occur at the higher concentrations. At the higher concentrations, the

incident photons are absorbed by the medium and no scattering takes place. We got SRS

emissions from 10-5 molar concentration onwards. As the concentration decreases, the amplitude

of the Raman emission also decreases. As the concentration decreases, the amplified stimulated

emission increases. This amplified stimulated emission inhibit the Raman scattering emissions.



RHODAMINE 6G IN ACETONE RHODAMINE B IN ACETONE

METHYLENE BLUE IN ACETONE RHODAMINE 6G IN 0.5 MOLAR

ACETONE



Therefore as the concentration decreases, the amplitude of the stimulated Raman emission also

decreases.

When we add methylene blue to acetone, the stimulated Raman scattering emission

observed from 10-5 concentration onwards. At the higher concentrations, the incident photons are

absorbed by the medium and no scattering takes place. As the concentration decreases, more

energy is transferred to the scattered photon. Therefore when the concentration decreases, the

amplitude of the Raman emission increases. But at a power level of 419 milli watt, as the

concentration decreases amplified stimulated emission also increases. It limits the SRS

emissions. So the amplitude of the the SRS emission also decreases.

When we add Rhodamine 6G to the 0.5 molar acetone, it is seen that, the stimulated Raman

scattering does not occur at the higher concentrations as in the case of 1 molar solution. At the

higher concentrations, the incident photons are absorbed by the medium and no scattering takes

place. We got SRS emissions from 10-5 molar concentration onwards. The amplitude of the

emission is large when compared to 1 molar solution. As the concentration decreases, the

amplitude of the Raman emission also decreases.



Fig: fluorescence spectrum of Rhodamine 6G

Fig: fluorescence spectrum of Rhodamine B

Fig: fluorescence spectrum of methylene blue



METHANOL

From observations, it is observed that the amplitude of the stimulated Raman scattering

emissions from pure methanol increases with incident power. As the incident power increases,

the scattered molecules get more energy. Then the amplitude of the emission increases with

power. At higher power levels, the Raman emission overcomes the amplified stimulated

emissions and the amplitude increases drastically.

When we add Rhodamine 6G to the methanol, it is seen that, the stimulated Raman scattering

does not occur at the higher concentrations. At the higher concentrations, the incident photons

are absorbed by the medium and no scattering takes place. We got SRS emissions from 10-5

molar concentration onwards. As the concentration decreases, the amplitude of the Raman

emission increases. When the concentration increases, the fluorescence emission and amplified

spontaneous emission inhibits the Raman emissions and the amplitude become decreases.

As we add Rhodamine B to the methanol, it is seen that, the stimulated Raman scattering does

not occur at the higher concentrations. At the higher concentrations, the incident photons are

absorbed by the medium and no scattering takes place as in the previous case. We got SRS

emissions from 10-5 molar concentration onwards. As the concentration increases, the amplitude

of the Raman emission almost constant.

Addition of methylene blue to the methanol, stimulated Raman scattering does not occur at the

higher concentrations because of the incident photons are absorbed by the medium and no

scattering takes place. We got SRS emissions from 10-6 molar concentration onwards. As the

concentration decreases, the amplitude of the Raman emission increases. When the concentration

increases, the fluorescence emission and amplified spontaneous emission inhibits the Raman

emissions and the amplitude become decreases. But in low power levels, when the concentration

decreases number molecules decreases and the scattering also decreases. It results in the

reduction of amplitude.



RHODAMINE 6G IN METHANOL RHODAMINE B IN METHANOL

METHYLENE BLUE IN METHANOL



METHYL ACETATE

From observations, it is observed that the amplitude of the stimulated Raman scattering

emissions from pure methyl acetate increases with incident power. As the incident power

increases, the scattered molecules get more energy. Then the amplitude of the emission increases

with power. At higher power levels, the Raman emission overcomes the amplified stimulated

emissions and the amplitude increases.

When we add Rhodamine 6G to the methyl acetate, it is observed that, the stimulated

Raman scattering does not occur at the higher concentrations. At the higher concentrations, the

incident photons are absorbed by the medium and no scattering takes place. We got SRS

emissions from 10-5 molar concentration onwards. As the concentration decreases, the amplitude

of the Raman emission increases. When the concentration increases, the fluorescence emission

and amplified spontaneous emission inhibits the Raman emissions and the amplitude become

decreases.

When we add Rhodamine B to the methanol, it is seen that, the stimulated Raman

scattering does not occur at the higher concentrations. At the higher concentrations, the incident

photons are absorbed by the medium and no scattering takes place. We got SRS emissions from

10-5 molar concentration onwards. As the concentration decreases, the amplitude of the Raman

emission slightly decreases because of low number of molecules. When the concentration

increases, the fluorescence emission and amplified spontaneous emission inhibits the Raman

emissions and the amplitude become decreases.

Methylene blue is not dissolved in methyl acetate. So characterization of stimulated

Raman scattering is not possible



RHODAMINE 6G IN METHYL

ACETATE

RHODAMINE B IN METHYL ACETATE

XYLENE

Xylene is not optically polarizable. So stimulated Raman emission does not occur in this

material. So characterization of SRS is not possible.

DEMINERALISED WATER

Stimulated Raman emission obtained in this material. But because of the very low amplitude at

very high power level, it can’t detect using ocean optics So characterization of SRS is not

possible.



9. CONCLUSION AND FUTURE WORK

Optical conjugation found wide application in optics field. One of the best method to attain

optical conjugation is stimulated Raman scattering. In this work, we studied stimulated Raman

scattering in different materials. Acetone, methanol, methyl acetate, xylene and demineralized

water are the research materials. We got stimulated Raman scattering from acetone, methanol

and methyl acetate because these are optically polarizable materials. It also observed the changes

in stimulated Raman scattering when we add dyes such as Rhodamine 6G, Rhodamine B and

methylene blue to the materials. It is found that the stimulated Raman scattering changes with

material, concentration and incident power level.

From the analysis we got, methyl acetate marked the lowest threshold for the stimulated

Raman scattering ie, 18 milli watt. It is found that the amplitude of the stimulated Raman

scattering emission varies with concentration. 419 milli watt is considered as the best power

level for this operation. All the three materials shows stimulated Raman emission in this power

level. Methyl Acetate found to be the best material for stimulated Raman scattering emission.

The quality of output can be increased by adding Rhodamine 6G to the methyl acetate solution.

One of the main application of this work is imaging. Stimulated Raman scattering also

used to analyze the properties of materials. In future we can develop a Raman laser where we can

use methyl acetate as the medium.



10. REFERENCES

http://www.rp-photonics.com/raman_scattering.html

Stimulated Raman scattering: old physics, new applications

Vladislav V. Yakovlev,1 Georgi I. Petrov,1 Hao F. Zhang,2 Gary D. Noojin,3 Michael L.

Denton,3 Robert J. Thomas,4 and Marlan O. Scully5,6

Stimulated Raman red-light generation by acetone as a perspective source for photodynamic

therapy applications

Author(s): Lorenzo Echevarria; L. Rodriguez; Vincent Piscitelli; O. Estrada; Aristides Alfredo

Marcano O.

Stimulated Stokes and anti-Stokes Raman scattering in liquid acetone with a Bessel beam

T. Manz *, U.T. Schwarz *, Max Maier ,Naturwissenschaftliche Fakult€at II, Universit€at

Regensburg, D-93040, Regensburg Germany

Stimulated resonance Raman scattering of Rhodamine 6G

Alfred S. Kwok and Richard K. Chang Department of Applied Physics and Center for Lasers

Diagnostics, Yale University, P.O. Box 208284 Yale Station, New Haven, Connecticut

Enhancement of stimulated Raman scattering of acetone and the generation of three-color laser

by using fluorescence dye RB

Juan Cheng1;2, Yinghong He1, Haoyi Zuo1, Jingguo Yang1

1Department of Physics, Sichuan University, Chengdu 6100642Research Center of Laser

Fusion, China Academy of Engineering Physics, Mianyang 621900



Nonlinear optical properties of selected laser dyes investigated using photo acoustics,

fluorescence and stimulated scattering

Reji Philip, department of physics, Cochin University of science and technology Cochin – 682022

Femtosecond stimulated Raman spectroscopy of methanol and acetone in a noncollinear

geometry using a super continuum probe

Mateusz Plewicki and Robert Levis, Department of Chemistry, Center for Advanced Photonics

Research, Temple University, Philadelphia, Pennsylvania 19122, USA

Efficient stimulated Raman scattering from picosecond pulses

M.J. Colles

Raman Spectroscopy and Microscopy: Solving Outstanding Problems in the Life Sciences

Dr. Marinella G. Sandros, University of North Carolina at Greensboro, and Dr. Fran Adar,

Horiba Scientific

of stimulated raman scattering in different materials

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