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AxoScanTM System Options and Measurement Solutions

AxoScan Mueller matrix polarimeters represent the most advanced polarization measurement systems available. This brochure describes standard system configurations, and a wide variety of measurements that can be made with the system.

Don’t see the system or solution that you need? Contact an Axometrics application engineer today to discuss your application.

Axometrics, Inc. 515 Sparkman Drive Huntsville, AL 35816 U.S.A. tel: 1-256-704-3332 fax: 1-256-704-6003 email: info@axometrics.com web: www.axometrics.com

All statements and technical information related to Axometrics products are believed to be accurate. However, the accuracy or completeness of this information is not guaranteed, and no responsibility is assumed for any inaccuracies. Axometrics assumes no responsibility for any damages whatsoever associated with the use or application of this product. Axometrics reserves the right to change the design, specifications, functions, or availability for sale of its products, at any time without notice. AxoScan, AxoView, Axometrics, and the Axometrics logo are trademarks of Axometrics, Inc. ©2004 Axometrics, Inc. all rights reserved.

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Standard AxoScanTM Systems

The Polarimeter Engine

All standard systems are based around the AxoScan Polarimeter Engine, the fastest and most accurate complete polarization measurement system available.

• Calibrated systems for the visible spectrum, near-infrared, and telecom wavelengths

• Extremely rugged – Ideal for laboratory or production use

• Can be held in any orientation

• Not sensitive to slight misalignments or vibration

• Variety of mounting options

• Tightly-integrated automation solutions available

• Turn-key operation

Mounting Fixtures

Several standard mounting fixtures are available to suit the needs of users in a wide range of different industries

• Light-weight extruded aluminum frame for stand-alone operation

• Mounts for horizontal operation on a standard optics table

• Brackets for vertical mounting on 1.5-inch pillar

Light Sources

Every application has a different light-source requirement. Axometrics offers several standard solutions, as well as systems that let you use your own light source.

• Temperature stabilized laser provides long-life at a single wavelength.

• Xenon Arc-lamp with scanning monochromator for spectral measurements across the visible wavelength range

• Connectors and integrated collimator for SMA- or FC-connectorized fibers lets the user supply nearly any light source

The AxoScan Polarimeter Engine

A variety of AxoScan mounting fixtures are available for different industries

Stabilized Laser

Filtered arc-lamp delivered through an optical fiber

FC-connectorized fiber for use with telecom wavelengths

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AxoViewTM Software Interface

All AxoScan polarimeters ship with the AxoView software interface pre-installed and ready to use.

• Simple control of the polarimeter hardware

• Powerful and intuitive data visualization

• System can be controlled remotely over RS-232 for integration into your automated test setup

SpectroPolarimeter Option

Tunable Visible Light Source

• Long-life Xenon arc lamp and grating monochromator

• Tune to any wavelength from 400 to 800 nm

• 5 nm spectral bandwidth

• Turn-key operation and seamless integration with the AxoView software interface

• Measure polarization properties across the visible spectrum in under five seconds

Advanced Spectral Analysis

• Visualization tools for analyzing polarization properties vs. wavelength

• Analyze any polarization property

• Includes routines for determining the true order of retarders

• Export data to spreadsheet files

• Export graphics to JPEG files for inclusion in reports and presentations

• Viewer software can be installed on multiple computers allowing exported data to be shared between technicians, engineers, and managers

AxoScan SpectroPolarimeter integrates a Xenon arc lamp

and scanning monochromator for measurements across the visible spectrum

Advanced visualization tools for interpreting polarization spectra. Here we see a measurement of a retarder with more than one

wave of retardance.

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Automated XY Table Option

• Generate easy-to-understand maps of parameters such as retardance, fast-axis orientation, polarizer axis, depolarization, percent transmission, etc.

• Flexible software for setting up scan parameters

• Measure up to 3 sites per second

• Standard system handles samples up to 6” square. Larger scan areas available upon request

Automated Tip-Tilt Table Option

• Automated, high-speed filed-of-view testing for all polarization optics

• Automatically locate and tilt about both fast- and slow-axes

• Out-of-plane retardance measurements

• LCD pre-tilt measurements

LCOS Retro-Reflection Fixture Option

• Directly measure retardance magnitude and orientation in retro-reflection

• XY scan table for mapping cell gap variations

• Measure retardance vs. voltage characteristics

• Advanced data reduction techniques remove the effect of the non-polarizing beamsplitter used for the measurement

XY scan table option for the AxoScan Polarimeter

Tip-Tilt table option for the AxoScan Polarimeter

LCOS retro-reflection fixture for the AxoScan polarimeter

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Measured retardance of a 10 nm trim plate

If the two plates of a compound zero-order waveplate are not perfectly aligned during manufacture, the orientation of the fast-axis can vary significantly, as shown in the measurement above.

Measured retardance map of a quarter-wave plate. The retardance is 90° in the center of the plate, but t here is a 15°

variation in retardance across the clear aperture.

Measuring Retarders and Waveplates

Films and Simple Waveplates

• Measure extremely low retardance, extremely large retardance, and everything in between

o Minimum measurable retardance about values as low as 0.25 nm (0.15° at 550 nm)

o Maximum measurable retardance >6,000 nm

• Measure retardance versus wavelength to determine dispersion relation of material

• Distinguish between fast- and slow-axes

• Measure axis orientation to within 0.1°

• Maps of spatial variation

• Off-axis / Field-of-view variations

Form-Birefringent Waveplates

• Measure retardance vs. wavelength characteristic

• Identify unexpected polarization-dependent transmission (diattenuation)

Compound Zero-Order and Achromatic Waveplates

• Measure optical rotation and elliptical fast-axes due to misaligned plates

• Fast-axis orientation variations with wavelength

• Measure retardance vs. wavelength characteristics

• Determine the true retardance order

• Actively align plates during assembly

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Measured maximum transmittance (for polarization state launched along transmission axis) for three different brands of linear

polarizers.

Measured output polarization state from the high-quality circular

polarizer (left-handed). The polarization state is shown graphically on the Poincaré sphere.

Measuring Polarizers

Crystal Polarizers

• Measure misaligned input and output polarizer axes due to improper construction

• Measure strong field-of-view variations as a function of wavelength

Dichroic Polarizers

• Performance vs. wavelength

o Max and Min transmittance

o Contrast ratio

o Polarizer Efficiency

• Field-of-view testing

• Measure transmission axis orientation to within 0.1°

• Spatial variations in transmission axis orientation

Reflective Polarizers

• Difference in transmitted and reflected contrast ratio

• Polarization axis orientation

Circular Polarizers

• Distinguish between left-hand and right-hand polarizers

• Determine transmitted polarization state as a function of wavelength

• Actively align retarders to polarizers

• Measure the retardance and axis alignment of a retarder in a complete circular polarizer

Polarizing Beam Splitters

• Spatial maps of transmitted and reflected properties

• Measure variations in polarizer axis due to stain birefringence

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Mounting a BK7 window with a set-screw induces very large amounts of strain birefringence. In this XY map, we see

retardance values as large as 22° at the contact po int

A window that glued into a mount exhibited 1.4° of retardance due to strain birefringence. Heating the part with a heat gun quickly reduces the strain down to a retardance of less than 0.2°. The retardance returns to 1.4° as th e part cools down

over the course of an hour.

A PET film with more than 10 waves of retardance can partially depolarize a beam with a 5 nm FWHM spectral bandwidth.

AxoView provides tools for visualizing depolarization effects.

A z-cut LiNbO3 device should have no retardance on-axis. Here, we measured 20° of retardance. Tilting the sample by 0.5° causes

the beam to refract into the true optic axis of the sample.

Measuring Optical Components

Windows

• Measure strain birefringence in optics before or after mounting

• Dynamic variations with temperature and adhesive curing

Depolarizers

• Measure which polarization states are depolarized and which are not

• Max, min, and average degree of polarization

• Identify causes of depolarization

C-Plates

• Measure the on-axis retardance of c-plates due to misalignment of the optic axis

• Identify the true orientation of the optic axis

• Locate the optic axis in z-cut LiNbO3 devices

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Circular retardance and optical rotation are two names for

the same effect. Here, we measured the optical rotation (in degrees) of an organic sample (approx. 17 mm or corn

syrup) as a function of optical wavelength.

Non-polarizing beamsplitter cubes frequently exhibit

retardance in transmission. Here we show an XY map of retardance, exhibiting significant variations in retardance.

A mounted 636 nm bandpass exhibits significant retardance

at normal incidence., likely due to strain birefringence. Notice that the retardance vs. wavelength curve is

significantly more complex than the 1/λ characteristic typical of strain birefringence in homogenous materials.

Optical Rotation / Optical Activity

• Measure optical activity / optical rotation

• Characterize magneto-optical devices

• Calculate sugar or alcohol concentrations

Beamsplitters and prisms

• Measure retardance resulting from total-internal-reflection within prisms

• Measure s– and p–reflectances and transmittances

• Characterize retardance due to propagation through thin-films at non-normal incidence

Bandpass Filters

• Measure retardance and polarization dependent loss of filters used an non-normal incidence

• Retardance due to strain birefringence

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Measured retardance variation of an LCOS device at 0V. The 41° of retardance variation is due to variation s in cell gap

across the device.

Measured eigenmodes (top) and retardance (bottom) of an

STN LCD cell. From these measurements, an inversion algorithm is used to calculate cell gap = 5.8 µm and

twist angle = 120°.

High speed measurements of all critical parameters of biaxial films and other

field-of-view enhancing technologies.

Measuring Display Components

LCOS Panels

• Make measurements in direct retro-reflection

• Measure strain birefringence in unfilled cells

• Directly measure cell retardance

• Measure retardance vs. voltage characteristics

• Map spatial variation in cell gap

o variation in retardance

o variation in fast-axis orientation

LCD Panels

• Complete characterization of any cell mode

• Direct retardance and eigenmode measurement

• Calculate cell-gap, twist angle and pretilt

Biaxial Films

• Characterize field-of-view enhancing films

• Accurate fast-axis orientation measurement

• Measure R0, Rth, and β

• 3D refractive index ellipse

• Automatically tilt about fast- and slow-axis

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An FC receptacle and collimator lets you use your

existing optical source. The AxoScan is compatible with a wide range of sources, including lasers, TLS, SLD,

ASE sources, etc.

Using a free-space AxoScan to characterize a waveguide

device. The output beam from the polarization state generator has been launched into the DUT, and the output has been

collimated for measurement by the polarization state analyzer.

Using a fiber-coupled AxoScan to characterize a WDM filter

Measurement of second-order PMD. In this case the

DGD remains nearly constant with wavelength while the PSP’s trace out an arc on the Poincaré sphere.

Measuring Fiber-Optic Components and Waveguides

Optical Source Options

• Axometrics-supplied single wavelength laser

• User-supplied source delivered to the polarimeter via FC-connectorized fiber

o tunable laser source

o super-luminescent diode

o broadband

Applications

• Characterize polarization controllers

• Measure PMD and PDL

o differential group delay

o principal state of polarization

• Full Mueller matrix measurement allows determination of high-order PMD

• Depolarization effects

• PM fiber alignment

Free Space Measurements

• Exceptional flexibility for the R&D environments

• Measure crystals prior to integration into fiber devices

• Launch a free-space beam into a waveguide or fiber device

Fiber-Coupled Measurements

• Adapters are available for directly coupling the AxoScan heads to fiber-coupled devices

o FC ports with integrated collimators