J. Larry Pezzaniti

Mueller matrix imaging polarimetry

The design and operation of a Mueller matrix imaging polarimeter is presented. The instrument is configurable to make a wide variety of polarimetric measurements of optical systems and samples. In one configuration, it measures the polarization properties of a set of ray paths through a sample. The sample may comprise a single element, such as a lens, polarizer, retarder, spatial light modulator, or beamsplitter, or an entire optical system containing many elements. In a second configuration, it measures an optical systems point spread matrix, a Mueller matrix relating the polarization state of a point object to the distribution of intensity and polarization across the image. The instrument is described and a number of example measurements are provided that demonstrate the Mueller matrix imaging polarimeters unique measurement capability.

Mueller matrix algorithms

A method for the correction of systematic errors generated by large orientational and retardance errors in the polarization optics in the dual rotating retarder polarimeter is presented. Small orientational and retardance errors (<1 degree(s)) can lead to large errors in the measured Mueller matrix (> 10% in some matrix elements). We incorporate correction terms for large orientation and retardance errors into the dual rotating retarder data reduction algorithm. Using these data reduction algorithms and a calibration step, the associated systematic errors are calculated and removed from the measured Mueller matrix. This procedure is especially useful for spectral and multi-wavelength systems in which the retardance and often the orientation of the retarders are wavelength dependent. The equations, the procedure to calculate the orientations of the polarization elements and the retardances of the retardation elements, and the method to correct for any errors are presented here. The effect of these errors on the calculated Mueller matrix elements and their correction is shown analytically and through experimental data taken on an infrared spectropolarimeter.

Angular dependence of polarizing beam-splitter cubes

The field-of-view dependence of polarizing beam-splitter cubes has been studied to characterize their behavior in imaging systems such as optical computers and optical correlators and in other applications that involve noncollimated light. Significant polarization aberration is present in polarizing beamsplitter cubes for two reasons: (1) the s- and p-component orientations, which define the polarizing axes, at the beam-splitting interface vary with the direction of propagation, and (2) the performance of the coating is a function of the angle of incidence. We describe the polarization aberration of a polarizing beam-splitter cube in terms of its diattenuation (polarizing efficiency). We use an imaging polarimeter to measure six figures of merit for three polarizing beam-splitter cubes demonstrating typical polarization aberrations. Finally, we derive the Mueller matrix for a polarizing beam-splitter cube in terms of the s and p transmittance and reflectance and the phase retardances, the parameters generally calculated with thin-film analysis programs.

Mueller matrix scatter polarimetry of a diamond-turned mirror

A novel technique for measuring the polarization light scattering function of surfaces using a Mueller matrix imaging scatter polarimeter is presented. This technique measures the near-specular scatter of reflective surfaces as Mueller matrix images, enabling the diattenuation, retardance, and depolarization of the scattered light to be determined. An example of measurements of a diamond-turned aluminum mirror with an rms roughness of 11.4 nm is presented and interpreted. The most surprising result in our data was that this scattering process created partially elliptical polarized light from unpolarized incident light, where we had expected essentially partially linearly polarized light.

Imaging polarimeters for optical metrology

Two configurations of imaging polarimeters are described that are designed for polaimetric optical metrology. The first is a Stokes imaging polarimeter which measures the polarization response of optical systems to spherical or planar waves of known polarization. The output is images of the degree of polarization, orientation, and eccentricity of polarization ellipses, or Stokes parameters displayed as a function of either the exit pupil or image coordinate of the optical system. The second configuration is a Mueller imaging polarimeter which measures the Mueller matrix of an optical system on a ray-by-ray basis. Calibration issues involved in building the instruments are addressed along with a brief discussion on polarization aberration mechanisms.

Depolarization measurements of an integrating sphere

Mueller-matrix polarimetry performed in the visible and near IR indicates that an integrating sphere acts as an ideal depolarizer to the 0.5% accuracy of the polarimeter. The integrating sphere emits unpolarized light regardless of the incident polarization state.

Linear polarization uniformity measurements taken with an imaging polarimeter

Four types of polarizers are experimentally evaluated and compared for the uniformity of their transmission axis orientations and the contrast ratio and their spatial variation. Representative samples of calcite Glan-Thompson polarizers, polarizing beamsplitters, silver glass polarizers, and stretched polymer polarizers are characterized at 850 nm using a rotating polarizer imaging polarimeter. The sample Glan-Thompson polarizers show the highest contrast ratios and greatest uniformity of transmission axis. Silver glass polarizers and stretched polymer polarizers show intermediate contrast ratios, but all samples of both show a systematic variation of the transmission axis orientation with a magnitude of several tenths of a degree. The polarizing beamsplitter cube samples have very good uniformity of transmission axis but the smallest contrast ratios with noticeable spatial variations of contrast.

High-resolution Mueller matrix imaging polarimetry for understanding high-resolution optoelectronic modulators

A high resolution Mueller matrix imaging polarimetry test bed has been constructed and calibrated that has unique capabilities for characterizing optoelectronic devices, such as liquid crystal modulators, PLZT modulators, quantum well modulators, and surface emitting lasers. Similarly, the instrument can perform end-to-end measurements on optoelectronic systems including optical computers, interconnects, and correlators. It addresses, at the systems level, the need for incorporating polarimetric analysis and measurement techniques into the design, alignment, and testing of photonics technologies. The polarimeter maps the polarization altering characteristics of optical devices and optical systems, producing means of the retardance, the diattenuation, and the depolarization. The polarization mappings may be obtained across individual pixels or across large pixel arrays. The data sets provide a wealth of information not otherwise accessible for characterizing device uniformity, operating parameters, angular bandwidth, as well as identifying non-ideal polarization characteristics.

Real-time total integrated scattering measurements on the Mir spacecraft to evaluate sample degradation in space

An instrument to measure total integrated scattering (TIS) in space was built as part of the Optical Properties Monitor instrument package and flown on the Russian Mir Space Station in a low Earth orbit. TIS at two wavelengths was measured in space at approximately weekly intervals from 29 April to 26 December 1997 and telemetered to Earth during the mission. Of the 20 TIS samples, 13 are described here to illustrate the performance of the TIS instrument. These include ten optical samples and three thermal control samples. Two optical samples and one thermal control sample were severely degraded by atomic oxygen. All samples received a light dusting of particles during the mission and an additional heavier layer after the samples returned to Earth. The initial brassboard instrument and the validation tests of the flight instrument are also described.

Total integrated scatter instrument for in-space monitoring of surface degradation

A Total Integrated Scatter (TIS) system was built to test the viability of a TIS instrument to be used in space to monitor damage to optical and thermal control surfaces due to the low earth environment. The systems accuracy and repeatability in detecting changes in the surface quality of various space materials after exposure to atomic oxygen was tested. A method for distinguishing roughening of a surface from dust contamination is described.