Elizabeth A. Sornsin

Multispectral infrared Stokes imaging polarimeter

We describe the design and development of an imaging polarimeter that will simultaneously measure Stokes vector images in the mid-wave IR and long-wave IR wavebands. We present an analysis of the expected errors that arise due to spectral variations in the polarization elements of the instrument across each waveband. FInally, instrument calibration and polarization images acquired in the MWIR waveband are presented.

Polarization signatures of spherical and conical targets measured by Mueller matrix imaging polarimetry

The polarization and depolarization properties of two types of targets have been derived from the experimental determination of their Mueller matrix image. Each polarization signature is deduced from the polar decomposition of the Mueller matrix into images of retardance, diattenuation, polarizance, and depolarization. Different correlations between the polarization parameters and synthesized angle of incidence and angle of scatter images have been developed to determine an approximation of the angle of incidence from the polarization signatures.

Visible Mueller matrix spectropolarimetry

A Mueller matrix spectropolarimeter operating between 400- 900nm has been developed for optical element characterization at The University of Alabama in Huntsville. Mueller matrices are measured as a function of wavelength and the spectral behavior of the polarization properties can be determined. Measurements of an achromatic retarder in transmission, a reflective beamsplitter, and the electro- optic dispersion of a spatial light modulator will be presented.

Alignment and calibration of an infrared achromatic retarder using FTIR Mueller matrix spectropolarimetry

An IR achromatic retarder was aligned and characterized using the University of Alabama in Huntsvilles Fourier transform IR spectropolarimeter. The FTIR spectropolarimeter produces a full polarization description of a sample over wavelengths 3-14 micrometers . Mueller matrices were measured for different relative alignments between the complementary plates of the achromat until the retardance orientation variation was reduced to within +/- 1 degree and the retardance magnitude varied smoothly with a peak-to-valley difference of 24 degrees from 4-14 micrometers . The results presented here include the progression of retardance magnitudes and retardance orientations as the plates alignment varied as well as the final Mueller matrix and retardance components of the achromat element.

Mueller matrix imaging of GaAs/AlGaAs self-imaging beamsplitting waveguides

Imaging polarimetry is a novel method of characterizing the polarization effects of optoelectronic devices. From the Mueller matrix image, any polarization property of a device can be determined. High resolution polarization images of the outcoupling faces of several self-imaging GaAs/AlGaAs waveguide beamsplitters were made in the Mueller matrix imaging polarimeter at the University of Alabama in Huntsville. Interesting polarization states of the device modes (TE and TM), the magnitude of linear retardance varied significantly across a device. Polarization losses were also observed to vary across the faces of the devices. These effects could not have been observed by simply measuring the crosstalk between the TE and TM modes. The results of this study could lead to the detection of defect mechanisms in optoelectronic devices through Mueller matrix measurements.

Electro-optic spatial light modulator characterization using Mueller matrix imaging

A series of electro-optic spatial light modulators have been measured with the Mueller matrix imaging polarimeter (MMIP). The MMIP is a dual rotating-retarder polarimeter which illuminates a sample with calibrated polarized states and analytes the existing polarized state over a spatially resolved image of the sample. Images of the retardance magnitude and retardance fast axis orientation reveal the relative electric field strengths in a device with lead- lanthanum-zirconate-titanate modulating material. By measuring Mueller matrix images of the device at several different applied voltages, a quadratic electro-optic coefficient of 2 X 10-16 (m/V)2 was determined in the modulator active regions.

HN22 sheet polarizer, an inexpensive infrared retarder

The popular sheet polarizer, Polaroid HN22, has been measured to be a nearly half-wave retarder in the 3.6-5.4-microm spectral band with a transmittance of approximately 20%. Tuning of the retardance value between 60 degrees and 260 degrees has been demonstrated by tilting of the HN22 sheet with respect to the incident beam. The materials availability, relatively large aperture, large field of view, and low cost make it an excellent candidate for use as an infrared retarder for systems operating in this wave band. Thus HN22 may be employed as an inexpensive half-wave linear retarder and used for rotating the plane of polarization as well as for conversion between circular polarization states.

Near-achromatic retardance behavior of HN22 Polaroid 3.6 to 5.4 μm

Polaroid HN22, a popular sheet polarizer, has been measured to be a nearly half wave retarder in the 3.6 to 5.4 micrometers spectral band with a transmittance of approximately 20 percent. The exact retardance value may be tuned to the range of 60 degrees - 260 degrees by tilting the HN22 with respect to the incident beam. The materials polarizing effects have been shown to be minimal in this waveband. Its availability, relatively large available aperture, large filed of view, and low cost make HN22 an excellent candidate for use as an IR retarder for systems operating from 3.6 to 5.4 micrometers . As such, HN22 may be used for rotating the plane of polarization of an incident linearly polarized beam as well as to convert between circular polarization states.

High-resolution Mueller matrix polarimetry of thin film PLZT electro-optic modulators

A thin-film lead-lanthanum-zirconate-titanate (PLZT) electro-optic spatial light modulator has been characterized with the Mueller matrix imaging polarimeter (MMIP). The MMIP is a dual rotating-retarder polarimeter which illuminates a sample with calibrated polarized states and analyzes the existing polarized state over a spatially-resolved image of the sample images of the retardance magnitude and retardance fast axis orientation reveal the relative electric field strengths in the PLZT 9/65/35 material. By measuring Mueller matrix images of the device at several different applied voltages, a quadratic electro-optic coefficient of 2 X 10-16 (m/V)2 was determined in the modulator active regions.

Mueller matrix polarimetry of electro-optic PLZT spatial light modulators

Mueller matrix polarimetry has been used to determine operational efficiency and material quality in lead- lanthanum-zirconium-titanate (PLZT) electro-optic modulators. PLZT is a transparent, quadratic electro-optic ceramic which is a candidate for the next generation of electro-optic interconnects and modulating devices. The Polarimetry group at the University of Alabama in Huntsville has measured Mueller matrices for several sample devices. The purpose of this study was to evaluate the optical quality of the transmissive PLZT devices, determine the uniformity of the modulation across the active area, and calculate the quadratic electro-optic coefficients. High- resolution imaging polarimetry has demonstrated the uniformity of the polarizing and polarization-scrambling properties of a bulk PLZT spatial light modulator array. The Mueller Matrix Imaging Polarimeter was used to produce magnified maps of device regions; this data provides insight to the material uniformity, proper contact of drive electrodes, distribution of the applied electric fields, and quality of the surface. Light scattering from ceramic grain boundaries was also observed to result in some depolarization of light exiting the device. A single-channel Mueller matrix polarimeter measured spatially-averaged device performance for a range of applied operating voltages. This information easily determined the electro- optic coefficients for the modulating material. Several chemical vapor deposited thin-film PLZT devices were studied, and the quadratic electro-optic coefficients compared favorably to that for bulk PLZT.