Nonlinear optics: Moving from the laboratory to applications

October 8, 2012

Peter Moulton Q-Peak, Inc.

Outline

• A few personal notes

• Harmonic generation

• Optical parametric oscillators

• Highly nonlinear optics

This is not an academic review by any means!

Harvard connection

First brush with nonlinear optics (1965) Physics meets the Beatles

Harvard connection - renewed

Ruby lasers enabled demonstrations of NLO

Pictures of first ruby laser at Hughes

My pursuits in linear optics bore fruit in 1982

Materials technology does matter!

Outline

• A few personal notes

• Harmonic generation

• Optical parametric oscillators

• Highly nonlinear optics

The parade of nonlinear crystals

• KDP (KH2PO4) family (inherited from acoustic transducers)

• Niobates - LiNbO3, KNbO3, Ba2NaNb5O12

• KTP (KTiOPO4) family

• Borates - BBO (β-BaB2O4), LBO (LiB3O5), BiBO (BiB3O6)

• Quasi phase-matched – Periodically poled (PPLN, PPSLT, PPKTP) – Orientation patterned (OP-GaAs)

12

Not always this easy to grow these big crystals

KDP (thanks to Cleveland Crystals, LLNL)

Uses for big crystals

Key to practical laser fusion?

Going Bananas – and then reality hit

16

KTP (and isomorphs)

• Features – High damage threshold – CPM for Nd SHG has large

acceptance angle – Relatively temperature

insensitive – Large apertures available for

high-energy systems – Isomorphs available for

special applications • Bugs

– Induced absorption limits average power in green

– High n2, self focusing – Damage centers (gray

tracking) form in bulk with green generation

– Explodes when absorbing energy too quickly

(KTA)

17

BBO

• Features – Large birefringence, allowing

phase-matching over a wide range

– Moderate nonlinearity – High damage threshold – Good UV transparency – Temperature insensitivity

• Bugs – Large birefringence, leading

to large walkoff and small angular acceptance

– Tendency to form damage centers with UV generation

18

BBO extends operation into the UV

19

Phase-matching angle vs. wavelength

400 600 800 1000 12000

10

20

30

40

50

60

70

80

90

FUNDAMENTAL WAVELENGTH (nm)

INTE

RN

AL

PHA

SE-M

ATC

HIN

G A

NG

LE (d

eg.)

BBO

LBO

KDP

TYPE I SHGd = 0

20

BAWS system uses UV-generating uchip laser

Thanks to NG Component Technologies

Bad things happen in the UV

Coping with bad things

Walk-off in birefringent phase-matching

Theory shows low walk-off focusing is better

Results with BBO 262-nm generation

Low-walkoff 3 W maximum power

High-walkoff 5.3 W maximum power

26

LBO

• Features – Very high damage threshold – Ability to operate with NCPM – Excellent UV transparency – Negligible bulk optical

absorption – No bulk damage ever

observed • Bugs

– Tricky to grow – Funky thermal expansion

makes coating difficult – Not enough birefringence to

generate 4th harmonic

27

Chen (on the right) credited with inventing LBO at Fujian (who is that other guy?)

28

LBO can be temperature tuned into NCPM

29

LBO NCPM SHG conversion approaches 70%

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

0 100 200 300 400 500 600 700 800

Intensity (MW/cm2)

Effic

ienc

y

Note: Intensity is peak in space and timeAverage spatial intensity is half the value shown

Data pointsTheory for 1.8-cm crystal

LBO-based systems can generate multi-100-W powers

The new MambaTM Green from Coherent Inc. is a frequency doubled, diode-pumped solid-state laser that offers an exceptional combination of high output power, outstanding reliability and low cost of ownership for a wide range of materials processing tasks. The Mamba Green delivers over 325 Watts of output at 532 nm (at 10 kHz), yet its integrated doubling crystal shifter and field replaceable gain modules provide an expected operating lifetime of over 25,000 hours.

Goodbye (and good riddance) to argon-ion lasers

Spectra-Physics Millenia (up to 15 W cw)

Coherent Verdi (up to 18 W cw)

Finally delivers the promise of cw green from 1968

Outline

• A few personal notes

• Harmonic generation

• Optical parametric oscillators

• Highly nonlinear optics

33

Time reversal of interactions is allowed

Nonlinear interaction ω1

ω2

ω3 = ω1 + ω2

Nonlinear interaction ω1

ω2

ω3 = ω1 + ω2

34

BBO OPO widely used in research lasers

Spectra-Physics OPO product

36

KTA OPO tuning curves, 1053-nm pump

1.4

1.6

1.8

2

2.2

2.4

2.6

2.8

3

3.2

3.4

3.6

45 50 55 60 65 70 75 80 85 90

Angle (deg.)

Wav

elen

gth

(um

)

Signal, x-cutIdler, x-cutSignal, y-cutIdler, y-cut

37

OPO resonator designs

pump

signal RING

pump signal

HT pump HR signal

PR signal HR pump

20 mm KTP STANDING-WAVE M1

pump

450 mJ, 10 Hz 41% conversion Limits: M1 damage Pump feedback

TIR prism

4, 10-mm KTP

240 mJ, 30 Hz 34% conversion No feedback No damage at full power

38

Photo and schematic of KTP ring OPO

39

Highest-energy OPO, NCPM KTP

0

100

200

300

400

500 15

71-nm

OPO

Outp

ut

0.2 0.4 0.6 0.8 1 1.2 1064-nm Pump Energy (J)

4.5 W average power

40

Plot of KTP and KTA IR transmission

3000 3200 3400 3600 3800 40000

20

40

60

80

100T = 75% @ 3297nm

T = 23% @ 3297nm

KTA 2cm KTP 2cm

Wavelength (nm)

%T

41

High-average-power eyesafe OPO uses KTA

0 20 40 60 80 100 1200

5

10

15

20

25

30

35

Pump Power (Watts)

Sign

al P

ower

(Wat

ts)

M.S. Webb et al. Opt.Lett. 23, 1161 (1998)

42

Biological standoff detection system used high-power KTA OPO

43

Lithium Niobate

• Features – Large nonlinearity – Large crystal sizes possible

• Bugs – Color centers form with

visible light generation, destroying phase-matching

– Relatively low surface damage threshold

– Surface acts as dust magnet due to pyroelectricity

• Rescued by QPM for OPO

applications

3” diameter stoichiometric crystals

44

Quasi-phase-matched materials operate by periodically changing sign of nonlinearity

J. A. Armstrong, N. Bloembergen, J. Ducuing, and P. S. Pershan, “Interactions between light waves in a nonlinear dielectric,” Phys. Rev. 127, 1918 (1962).

Periodic reversal possible in ferro-electrics

46

Marty Fejer (on the left) led development of PPLN. Who is the other guy?

47

PPLN material (HC Photonics)

Standard Lengths* 10, 20, 30, 40 and 50 + 0.05 mm

Thickness 0.5 / 1.0 mm(+ 0.05 mm) typical

Width* 5 mm (+ 0.05 mm)typical

Single grating period > 4 mm

Multi-grating periods 6.5 ~32 mm

Damage Threshold 300 MW/cm2 (10ns, 1064nm)

48

QPM of PPLN OPO allows mid-IR generation

VIPER system protects aircraft against heat-seeking missiles (MANPADs)

Fundamentals of color displays

• In order to display a full range of colors, electronic displays that project images on a screen must combine red, green and blue light

• Conventional projectors with lamps as light sources take the white light from the lamp and separate out the red, green and blue colors with filters

• Lasers can be used as light sources, and in prior systems three lasers were needed for each color

51

High-power RGB source uses LBO in all nonlinear stages

Pump Laser SHG

1047 nm 523 nm

OPO

SHG

SHG

898 nm

1256 nm

449 nm

628 nm

Blue

Green

Red

Pump LaserPump Laser SHG

1047 nm 523 nm

OPO

SHGSHG

SHGSHG

898 nm

1256 nm

449 nm

628 nm

Blue

Green

Red

A temperature-tuned NCPM LBO OPO is the key element in the system

600700800900

1000110012001300140015001600170018001900

100 110 120 130 140 150 160 170 180

Temperature (C)

Sign

al, i

dler

wav

elen

gth

(nm

)

IdlerSignal

523.5-nm pump

First projection attempts lacked color balance

Successful spin-out

Salem, N.H. -- Laser Light Engines (LLE), a Salem-based developer of laser illumination technology for high-brightness digital projection, announced it has raised $9 million in venture funding, with an additional $6 million anticipated from new investors, bringing the company’s total new funding to $15 million. Founded in 2008, LLE manufactures laser-driven color modules and illumination engines for high-brightness performance projection, signage and lighting applications. The company said the new investment funds will be used to support product rollouts, and strengthen its engineering, sales and manufacturing operations. LLE has now raised $27 million in private funding since its founding. http://www.laserlightengines.com

Outline

• A few personal notes

• Harmonic generation

• Optical parametric oscillators

• Highly nonlinear optics

Kerr-lens modelocking (KLM) provides a fast switch to enable femtosecond generation

AO-MODULATOR

GVD COMPENSATINGPRISMS

Ti:SAPPHIRECRYSTAL

BRF

PUMPAO-MODULATOR

GVD COMPENSATINGPRISMS

GVD COMPENSATINGPRISMS

Ti:SAPPHIRECRYSTAL

Ti:SAPPHIRECRYSTAL

BRF

PUMP

Femtosecond OPOs based on Ti:sapphire

Tunable, high-repetition-rate, femtosecond pulse

generation in the ultraviolet M. Ghotbi, A. Esteban-Martin, and

M. Ebrahim-Zadeh,*

ICFO-Institut de Ciencies Fotoniques, Mediterranean Technology Park, 08860 Castelldefels, Barcelona, Spain

Institucio Catalana de Recerca i Estudis Avancats,

Passeig Lluis Companys 23, Barcelona 08010, Spain *Corresponding author: majid.ebrahim@icfo.es

Counting optical cycles (KLM + SESAM)

Seriously- nonlinear optics (O(20))

Lucent Technologies

R. Windeler J.K Ranka, R. S. Windeler, A. Stenz, Opt. Lett. 25, 25 (Jan. 2000)

Microstructured fiber dispersion zero at ~800 nm pulses do not spread continuum generation via self-phase modulation

-70

-60

-50

-40

-30

Det

ecte

d Po

wer

(dB

m)

1200 1000 800 600 400 Wavelength (nm)

Pre-fiber (Ti:Sapph)

After fiber

• How can we control the absolute frequencies (and hence the group-phase velocities)? Self-referencing

460 480 500 520 540

Fundamental-Second Harmonic

Beats

Repetition Rate

RF P

ower

(10

dB/d

iv)Frequency (MHz)

D. J. Jones et al, Science 288 p 635 28 April 2000

J. Reichert et al., Opt. Comm. 172 pp 59–68 15 Dec 1999

H. Telle et al., Appl. Phys. B 69, 327–332 8 Sept 1999

Locking via Self-ReferencingTechnique

Beat frequency at overlap = δ

Stockholm December 10, 2005

Hansch and Hall win Nobel Prize for Optical Combs

Photonic crystal fiber and microchip laser enable low-cost supercontinuum source

The supercontinuum source shown is built from a NL-1040 PCF pumped by a nanosecond 1064 nm microchip laser.

http://www.crystal-fibre.com/support/Supercontinuum%20-%20General.pdf

microchip laser

Chirped pulse amplification (CPA) avoids NL effects

Courtesy: Wikipedia 1985 (G.Mourou & D.Strikland)

Filaments

This type of propagation is called filamentation or self-guided propagation. filamentation of femtosecond laser pulses was shown to occur over more than 50m in Laboratoire d’Optique Appliquee, (see Fig. 1) and then over several hundreds of meters. Experiments in Spring 2003 at Ecole Polytechnique have revealed an horizontal filamentation over a distance larger than 2 km.

Experiments of vertical propagation suggest even larger filamentation distances.

Mechanism for filament formation in air

Photograph of Ti:sapphire-generated filament

Attosecond pulses, high-harmonic generation

CPA pushes to a Zettawatt (courtesy Mourou)