Optical phase modulation with a photoelastic modulator (PEM) and synchronous detection provides a convenient and versatile method of penetrating optically dense scattering media to yield information concerning (a) the chemical structure of the ambient medium, (b) the size and concentration of the suspended scattering particles, and (c) the presence and surface properties of embedded target objects. The salient experimental feature upon which the method is based is that only light which remains polarized contributes to output photocurrents at harmonics of the modulation frequency. Equivalently, polarimetric detection selects those photons which have undergone fewer depolarizing collisions than average. For the PEM configuration employed to delineate embedded objects, signals at (i) the modulation frequency f and (ii) first harmonic 2f respectively give nearly instantaneous measures of the difference in scattered intensities of (i) left and right circular polarizations and (ii) (sigma) and (pi) linear polarizations. Objects can be discerned, therefore, to the extent that (1) they scatter orthogonally polarized states of light differently and (2) the corresponding scattering from particles suspended in the surrounding medium cancels. Examination of different kinds of targets has shown that polarimetric imaging is sensitive to edges, surface texture, and absorption of the embedded object.

An imaging ellipsometer has been developed which employs phase shifting interferometry to characterize the ellipsometric parameters. Polarized light from a laser or incoherent source is collimated and reflected off of the surface under test. A modified Michelson interferometer is used in conjunction with a Wollaston prism to generate two interferograms with orthogonal polarization states. Subtraction of the phases in the two interferograms yields the ellipsometric parameter (Delta) . The fringe modulation of the two interferograms is used to calculate the ellipsometric parameter (Psi) . The instrument uses imaging optics to image the surface under test to a CCd, yielding a truly two dimensional ellipsometric measurement. The deign of the instrument and result of measurement will be presented.

A system for measurement of waveplate retardation using a photoelastic modulator will be described. The system is intended for incoming quality inspection of quarter-wave plates at 632.8 nm and 900 nm. Measurement of several polymer waveplates were in good agreement with the waveplate manufacturer's calibration data.

A method for measurement of low-level strain birefringence in optical elements and materials will be described. This method provides for the simultaneous measurement of magnitude and direction of the net retardation without the necessity of sample rotation. Good agreement was obtained between measured retardation and independent measurements of a polymer waveplate. Measurements were also made of uncalibrated samples with retardation magnitudes down to 1.5 nanometers.

An IR achromatic retarder was aligned and characterized using the University of Alabama in Huntsville's 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.

We examine the low light level performance of a four channel polarimeter with a single photon counting sensor associated with each channel. Specifically, we investigate how the detection noise propagates through the polarimeter calibration matrix and affects the estimation of each intensity and mutual phase retardance. The variance is derived for each of these quantities as a function of polarimeter design, detector read-out noise, and average detected photon-electron count. Based on these variances, a metric is defined which can be used to optimize the design of the polarimeter. A specific polarimeter design is examined for high and low light levels. Performance curves are shown for various polarization input parameters and light levels.

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.

Physics Innovations Inc. has developed polarization- sensitive thermal imaging sensors with high spatial resolution. In this paper we describe a method where video frames are captured and processed into images of the target's temperature distribution and the target's 3D shape and orientation. We demonstrate that the two angles of surface orientation can be determined for every point on a target. The geometric shape of a target can be determined simultaneously with the temperature distribution over the field-of-view. With high sped signal processing, high- resolution polarimetric data can be captured and displayed in real time and at frequency.

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.

A polarimeter system has been developed to investigate the reflected light of very rough non-specular surfaces. One special application is the polarimetric analysis of road surfaces to find features for the classifications relating to type and surface condition. The reflected light of such a surface varies very much depending on the inhomogeneous surface structures. The aim was to build a measurement system which is relatively insensitive to the positioning of the surface sample, is easy to calibrate and offers a high scanning rate. These demands lead us to a polarimeter setup using a combination of a four-detector-polarimeter and a retarder-polarimeter with liquid-crystal cells as retarding elements. With the help of this laboratory system it is possible to find all polarization depended features. In a further step the setup will be simplified to measure only selected values but with higher speed. The software of the system allows the complete control of the polarization generator and of both polarimeters including the calibration,the operation in different modes, the evaluation and graphical visualization of the measuring data.

In this paper we consider the physical interpretation of eigenvalues and eigenvectors in the coherency matrix formulation of optical polarimetry. The coherency matrix formulation is relatively new in optics and so is first developed and compared with the classical Mueller matrix formulation. It is shown that by employing a special kind of averaging based on a Bernoulli multi-symbol model using the eigenvector decomposition, physical parameters of the medium may be related to matrix observables. To illustrate this approach, the problem of scattering by a cloud of anisotropic particles with variable stochastic properties is used. It is shown in particular that a 2D plane, the entropy/alpha plane, is important for the representation of scattering data. The technique has potential application in data inversion studies in optical scattering polarimetry.

Retroreflection by a rough surface is defined as a brightness increase of the surface as the source-surface- observer angle is decreased to exactly zero degrees. The retroreflectance peaking has been acknowledged to be caused in two ways: (1) geometrically, by interparticulate shadowing, or (2) by physical interference caused be weak field localization of temporally and spatially coherent incident radiation scattered by surface edges or asperities. The distinction between the two is suggested as occurring when the correlation widths of the surface edges and asperities are on the order of or less than the coherence length of the incident wavelength. Anomalous unexplained repeatable polarized multiple retro-peaking occurs for many surfaces, adjacent to the main retroreflection peak. To test the applicability of the two theories of retroreflectance, direct and cross polarization data are presented on 18 substances in various configurations at high and low spatial resolution using a HeNe laser at 0.6328 micrometers wavelength. Depolarization of the incident coherent radiation is a significant factor to characterize the retroreflection phenomenology.

A decomposition for Mueller matrices into three physically descriptive components was recently developed by Shih-Yau Lu. The effect of experimental error on this decomposition was studied. Both analytical and numerical methods were employed. Symbolic expression of the component matrices in terms of the original Mueller matrix elements shows how errors in the original matrix propagate through the decomposition. Complete symbolic decomposition was given for non-depolarizing Mueller matrices and their associated physical parameters; however, the depolarizing case produced unmanageably large expressions, so approximations were used. For the numerical results, Mathcad was used to randomly generate Mueller matrices, incorporate matrices is proportional to the original error within the measured Mueller matrix, and that the proportional constant increases with each subsequent step in the decomposition. In addition, Cloude's method for eliminating 'noise' in a Mueller matrix was employed, and its effect on error distribution was analyzed.

The Mueller matrix completely characterizes scattered electromagnetic waves. It relates the incident to the scattered Stokes vectors. The Mueller matrix which contains intensity and relative phase data is very useful for remote sensing. The Mueller matrix , characterizing scattering from uniformly coated 2D random rough surfaces are assumed to be homogeneous, and isotropic with a Gaussian surface height joint probability density function. The diffuse, incoherent and coherent contributions to the Mueller matrix elements are evaluated. The Mueller matrix elements are more sensitive to the changes in the rms slope than to changes in the rms height. The element M₃₄ equals M₄₃ is most sensitive to variations in the thickness of the coating layer. This result could be used to estimate the thickness of the coating material. The magnitudes of the Mueller matrix elements are considerably more sensitive to changes in dissipation in the coating material than to changes in dissipation of the substrate.

The full wave solution for scattering from 2D irregular layered structures is expressed a sum of the radiation fields, the lateral waves, and the surface waves. Only the radiation far fields are considered in this work, since excitations of plane waves are considered and the observation points are in the far field region. The like and cross polarized diffuse scattered fields are derived for three medium irregular structures with 2D rough interfaces. The thickness of the coating material or thin film between the two interfaces is assumed to be constant. Thus in this case both interfaces are rough and there are five different scattering processes identified in the full wave results. The full wave diffuse scatter solutions reduce to the perturbation solution when the surface rms heights and slopes are very small and of the same order of smallness. When the surface radii of curvature and rms heights ar very large the full wave scatter solutions reduce to the physical optics solutions. The polarimetric solutions can be applied to remote sensing of dielectric coating materials on rough surfaces.

TASAT is a detailed tracking and controls simulation developed for modeling electro-optic tracking and imaging scenarios. In our work, the polarization rendering capabilities of TASAT have been exploited to arrive at a methodology for modeling coherent polarized speckle backscatter from an illuminated object. For coherent illumination, we form a complex combination of the polarized rendered fields with random phase and propagate them to the far field to simulate polarized speckle. The speckle return is then analyzed using a four-channel polarimeter model to yield four Stokes parameter fields. We review the approach used in developing the TASAT polarization rendering model and its extension to obtain polarized speckle and Stokes parameter fields. We then show that the simulation provides results which agree with theory and which illustrate polarization measurement variations with object constituent material properties and different object models. Stokes parameter spatial statistics are used to analyze simulation results. Our results suggest that these statistics may be useful in characterizing the effective polarization properties of object materials and for providing a diagnostic signature for some object.s

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.

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.

We propose a scheme of two-beam interferometry based on spatial separation of two optical arms by combining a doubly refracting element and a common mirror for the two interferometric arms. The scheme allows for a significant reduction of noise level and the detection of light-induced refractive index changes with high accuracy.

The polarization of light scattered out of the pane of incidence was measured from rough and microrough silicon, polished fused silica and glass ceramic, and ground and polished black glass. The measurement defects, demonstrating that the polarization light can be used to distinguish between microroughness and subsurface defects.

NIST has developed a Standard Reference Material that can be used to calibrate polarimetric instruments and improve measurement accuracy. The device, based on concatenated Fresnel rhombs, provides nominally 90 degrees retardance at 1319 nm, with the actual value known within +/- 0.1 degrees. The design of the retarder is reviewed, and the stability of retardance over time is discussed. A procedure for certification is outlined.

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 material's 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.

Complete specification s for commercially available polarizers and retarders are often not available, incomplete, or inaccurate. We analyze several commercial polarization elements using Mueller matrix polarimetry. Elements are characterized in terms of their diattenuation, retardance, and depolarization. Measurements were made with laser polarimeters and a spectropolarimeter.

The three independent characteristics of a polarizer are transmittance, extinction ratio, and cross-polarized scattering. Extinction ratio, depolarization, incoherent near-specular scattering (NSS), and contrasts are mutually dependent. Spectra of transmittance, extinction ratio, depolarization, and contrast for wiregrid polarizers were measured in the 3- to 5-micrometers wavelength region using the zones average method developed in this paper. Good polarizers are hard to find in this region. By putting two polarizers in a series with the polarization axes parallel to each other, the extinction ratio can be improved greatly by the ratio of total NSS to cross-polarized NSS of the rear polarizer.

In this paper we investigate the polarization properties of uncoated and coated parallel-slab multi-reflection beam splitters. We analyze the ellipsometric parameters and fractional powers for the multi-reflected components generated by this system. Interesting new observations regarding the polarization properties at the Brewster angle of incidence and distribution of powers among the multi- reflected components orders are presented.

An analysis is made of the effect of tiled-poling-induced birefringence on the polarization conversion in single mode waveguides. A polarization-independent electro-optic modulator with continuous-electrode structure for high speed modulation is designed by using formulae deduced from coupled mode theory. This device uses a Mach-Zehnder structure where both arms are constructed using tilted poling. The same device can be operated in two different modes. One is common-mode which has the advantage of polarization preserving, while the other is differential- mode which features a low driving voltage. An estimation of the influence of misalignment of the poling electrodes on the extinction ratio shows a large fabrication tolerance.

In this paper, a fiber-optic polarimetric temperature sensor is presented. As the sensing element, a single-mode fiber coiled on a cylindrical former with a high thermal expansion coefficient is used. For the construction of a very small sensor, a special fiber with very low bending losses is chosen. The birefringence of the fiber changes with former radius and is determined by suing a measurement setup for full polarization transfer matrix analysis of the sensor. This scheme is independent on fiber leads.

In this study, we have measured the IR polarization characteristics of several surfaces that are close to being Lambertian, such as flowers of sulfur and gold-coated sandpaper. The measurements were carried out by using a CO₂ laser as the source of radiation and irradiating the sample with either s or p polarized radiation. A polarizer in front of the detector could be set in the s or p position. It was found that the more Lambertian the sample, the lower the degree of polarization produced by it. Quantitative results are presented for the degree of polarization of the scattered radiation for all the surfaces studied. The results are correlated with the measured 'slope' of the surfaces.

Relatively little work has been performed to investigate the potential of polarization techniques to provide contrast enhancement in natural scenes. Largely, this is because film is less accurate radiometrically than digital CCD FPA sensing devices. Such enhancement is additional to that provided by between-band differences for multiband data. Recently, Kodak has developed several digital imaging cameras which were intended for professional photographers. The variant we used produced images in the green, red and near IR, simulating CIR film. However, the application of linear drivers to read the data from the camera into the computer has resulted in a device which can be used as a multiband imaging polarimeter. Here we examine the potential of digital image acquisition as a potential quantitative method to obtain new information additional to that obtained by multiband or even hyperspectral imaging methods. We present an example of an active on-going research program.

The Moderate Resolution Imaging Spectroradiometer (MODIS) will be one of the primary instruments observing the earth on the earth observing system scheduled for launch in mid 1998. Its 36 spectral bands ranging from 0.4 to 14.4 microns will image the entire earth. The radiometric requirements are such that the instrument's polarization sensitivity must be very well understood. This paper will describe the experimental setup, some of the experimental results and the accompanying analysis. Emphasis will be on an anomalous, 'four theta' experimental results and its explanation.

Relatively little work has been performed to investigate the potential of polarization techniques to provide contrast enhancement in natural scenes. Largely, this is because film is less accurate radiometrically than digital CCD FPA sensing devices. Such enhancement is additional to that provided by between-band differences for multiband data. Recently, Kodak has developed several digital imaging cameras which were intended for professional photographers. The variant we used obtained images in the green, red and near infrared, simulating CIR film. However, the application of linear drivers to rad the data from the camera into the computer has resulted in a device which can be used as a multiband imaging polarimeter. Here we examine the potential of digital image acquisition as a potential quantitative method to obtain new information additional to that obtained by multiband or even hyperspectral imaging methods. We present an example of an active on-going research program.

A multipurpose field radiometer was modified to measure the degree of polarization and radiance of the skylight either from the ground or from a ship. The atmospheric observations were performed at NASDA's Earth Observation Center in wavelengths from 400nm to 1000nm. It then decreased with a further increase of wavelength. This trend might be explained by contamination of relatively large aerosols in the atmosphere, while optical characteristic are rather insensitive to wavelength. Furthermore, observations were made on the campus of the Chiba University, off the west coast of Kyushu Island and at the Meteorological Research Institute. Comparisons are discussed.

Relatively little work has been performed to investigate the potential of polarization techniques to provide contrast enhancement information for vegetation mapping, and for vegetation condition assessment. Largely, this is because film is less accurate radiometrically than digital FPA sensing devices. Since polarization studies necessitate the differencing of images obtained with a linear polarizer rotated about the optic axis of a camera between sequential exposures, and since some of the differences are small, film has generally lacked the radiometric accuracy needed to reliably record such differences. Kodak has developed a high spatial resolution camera, and the development of linear drivers to read the data from the camera into the computer has resulted in a device which can be used as a multiband imaging polarimeter. Here we examine the potential of digital image acquisition as a potential quantitative method to obtain new information uncorrelated with that obtained by more conventional multiband imaging methods. Such information can potentially be used to form more sensitive vegetation indices, to differentiate species, and to penetrate canopy. We present promising examples of an active on-going research program.

In recent applications using an optical specular even detector (OSED I), a plane-polarimetric active-imaging system, results have shown that water surfaces supporting breaking gravity waves are efficient depolarizing scatterers at both microwave and visible wavelengths. Correlations of backscatter cross-section and degree-of-polarization with a polarimetric and range-gated radar at X-band wavelengths have shown good quantitative spatial and temporal agreement in laboratory experiments despite the great disparity in wavelengths. These correlations in conjunction with a temporally-synchronized side-looking camera have been crucial in the direct verification of conjectures concerning the scattering nature of ocean surfaces which have arisen from the study of ocean microwave backscatter experiments. In order to further understand the scattering process, a complete polarimetric characterization of the scattering surfaces is imperative. While advanced microwave systems presently provide full plane-polarization transmit-receive backscatter-cross-section matrices in horizontal and vertical polarization of the scene within the antenna footprint, a full Stokes-parameter description of a scattering scene is not easily obtained in the microwave regime. However, a Stokes-parameter imager at optical wavelengths appears to be feasible. We will discuss a new successor to our present OSED I to achieve this goal. OSED II will measure the four Stokes parameters using four CCD imagers viewing the same scene along the same optical axis via a single-aperture four-imager prism camera system. Appropriately chosen polarization filters in front of each imager will provide the polarimetric analysis capability. This instrument will allow the unambiguous specification of the orientation of the plane polarized component, and allow experimental assessment of the importance of any unpolarized component and of the possibility of any circularly polarized component. The complete Stokes parameter characterization of the breaking wave as a scattering surface will provide important information to guide the interpretation of microwave backscatter from ocean surfaces. The OSED II detection system will also be applicable to the general polarimetric description of remotely sensed scattering surfaces.

We have investigated the influence of atmospheric aerosol on the degree of linear polarization P of diffusely transmitted radiation within the O₂-A band, between 755 and 775 nm. In this wavelength interval, the molecular absorption optical thickness of the atmosphere ranges approximately from 10^-3 to 2 X 10², whereas the atmospheric molecular scattering optical thickness is an small as 0.025. Radiative transfer calculations have been performed for a terrestrial-like atmosphere to calculate P of the transmitted radiation as a function of the atmospheric molecular absorption optical thickness. Results are presented both for a clear atmosphere and for aerosol loaded atmospheres. It is shown that for small absorption optical thicknesses P is mainly determined by first order scattering by particles in the lower atmospheric layers. For absorption optical thicknesses larger than about 10, the degree of linear polarization of the transmitted radiation is dominated by P of the radiation that has taken the shortest optical path through the atmosphere. For the zenith sky radiation, P is then mainly determined by single scattering in the upper atmospheric layers. For radiation from other directions, P then largely results from two scatterings: the first one by particles in the upper atmospheric layers in the nadir direction, and the second one by particles in the lower layers. It is concluded that information on tropospheric aerosol particles can be derived from polarization measurements of the diffusely transmitted radiation outside the O₂-A absorption band. In the strongest parts of the band, zenith sky polarization measurements contain information on the stratospheric aerosol particles.

POLDER has been launched on the Japanese ADEOS platform in August 1996. Due to its multi-directional, multispectral and multi-polarization capabilities, this new radiometer gives useful information on the clouds and on their influence on the radiation in the shortwave range. The POLDER bidirectional observation capability provides the polarization signatures within a large range of scattering angles in three spectral bands centered on 443, 670 and 865 nm with a spatial resolution of 7km X 7km. These original features allow to obtain some information both on cloud thermodynamic phase and even on the cloud microphysic of particles. Cloud phase recognition is important for cloud studies. Ice crystals correspond to physical process and properties that differ from those of liquid water drops. The angular POLDER airborne observations, liquid cloud droplets exhibit the very specific polarization features of the rainbow for scattering angels near 140 degrees. Conversely, according to theoretical studies and also to airborne measurements, scattering by various crystalline particles all show that the rainbow characteristics disappear as soon as the particles depart from the spherical shape. In the paper, preliminary results about cloud observations using polarized light measured by the spaceborne version of POLDER are presented, with emphasis on cloud phase detection and microphysic retrieval.

The POLDER instrument has been launched aboard the Japanese ADEOS platform in August 1996. In the paper, we shall describe the aerosols retrieval algorithms both over land surfaces and ocean surfaces. Over ocean surfaces, we use the classical method based on the spectral dependence of the near IR radiances. The directional effect is used to mean the results and to avoid the sunglint. The polarized radiances give some information about the refractive index. Over land surfaces, it has been suggested long ago that polarization could offer a powerful tool for remote main reason why some spectral bands of the instrument have been devoted to polarization measurements. The algorithm uses the bidirectional polarized observations within a large range of scattering angles in three spectral bands centered on 443, 670 and 865 nm. Calibration validation phase should be over around the middle of 1997, then the validation of the POLDER 'scientific results' will start. Preliminary results concerning aerosols retrieval will be presented: global aerosol optical thickness map, microphysics and comparison with in-situ measurements.

An imaging radiometer is one of the most fundamental optics sensors for aircraft as well as satellite remote sensing. The important points on the future imaging radiometers are hyper-spectral resolution, wavelength running capability, and polarimetry would give us further information. The basic problem is the requirement for two simultaneous photometric measurements of every point in the sensor field of view for the two orthogonal polarization components. Then we developed a tunable spectral and polarimetric radiometer: an AOTF imaging spectro-polarization components. Then we developed a tunable spectral and polarimetric radiometer: an AOTF imaging spectro-polarimeter which uses an acousto-optic tunable filter (AOTF) as spectroscopic as well as polarimetric element. The specific point of the device is that we can simultaneously obtain two diffracted beams and images perpendicularly polarized to each other. The instrument employs an reviewing the concept, configuration and performance of the instrument, applications of the instrument will be presented: the laboratory measurements of light scattering by rough surfaces, the aerosol measurements from the ground, and more.

Ground-based observations of zenith sky polarization have been performed with the GOME breadboard model. This spectrometer operates at high spectral resolution while at the same time covering a broad spectral range from the UV into the near-IR. Spectral fine-structures have been observed in the zenith sky polarization which are related to the ring effect and to molecular absorption in the atmosphere. First results obtained on a clear sky day are presented.

Techniques for the partial or complete determination of the Mueller matrix of elastic light scattering by a given samples are reviewed. Important developments include several implementations and applications of the dual-rotating- retarder Mueller-matrix ellipsometer and the addition of imaging, scanning, and spectroscopic capabilities. The use of a multi-channel division-of-amplitude photopolarimeter as a polarization state detector, and the propose modulation of the polarization state generator have substantially increased the efficiency and speed with which the full Mueller matrix can be measured.

The com;lex amplitude reflection and transmission coefficients for the p and s polarizations at oblique incidence are determined for a four-port solid-substrate Fabry-Perot/Michelson interferometer. The amplitude response for each of the two reflected and two transmitted waves is considered as a function of the angle of incidence and optical path length. Incidence angles for maximum back reflection and maximum back transmission are noted for both polarizations. The presence of multiple ports enables four ellipsometric functions to be measured simultaneously, which is desirable for the accurate and unambiguous characterization of deposited thin films. Results are presented for reflection and transmission ellipsometry of a growing transparent MgF₂ film on the planar entrance face of a ZnS-prism interferometer.

There have been many recent manifestations of geometrical phases in optics, but in the majority of publications, both theoretical and experimental. These phases are considered only as some interesting natural phenomena. Nevertheless,the information contained in geometrical phase can be used for constructing the devices capable of measurement both geometrical and optical characteristics of a micro-surface, which combine the properties of profilometer and ellipsometer. The practical aspects of the fundamental theory of geometrical phases in the non-planar 3D- interferometer are applied for a micro-surface measurements. The proposed interpretation allows to consider components of the dynamic phase and the geometric phase separately in an interference pattern. This concept provides the following micro-object characterization: refractive index, extinction ration, pixel planar angles, polarization optical constants. In order to identify the geometric phases the ellipsometer techniques are applied and a spatial distribution of the Jone's matrix is calculated. The measurement procedure is developed for the anisotropic objects as well. The role of the geometric phases is rather important when a high magnification mode of the interferometer is adjusted.

This work presents an aerosol model interpreting photopolarimetric measurements of skylight over the ocean. Polarization degree and optical thickness of the atmospheric constituents have been simultaneously measured by a photopolarimeter, whose spectral bands are set up to correspond to the ADEOS/POLDER. Our algorithms are based on light scattering simulations of the polarization field. It is shown that such a Maxwell-Garnett mixing rule as small water-soluble inclusions is an oceanic matrix is available to interpret the polarization measurements over the Seto Inland sea and its volume fraction of inclusions to matrix varies with time polarimetric properties of atmospheric aerosols, and that magnitude of polarization degree is reduced due to multiple scattered light, especially in the visible wavelengths.

Representing the areal extent of circumpolar wetlands is a critical step to quantifying the emission of methane, an important greenhouse gas. Present estimates of the areal extent of these wetlands differ nearly seven fold, implying large uncertainties exist in the prediction of circumpolar methane emission rates. Our objective is to use multi- directional and polarization measurement provided by the French POLDER sensor to improve this estimate. The results show that wetlands can be detected, classified and their area quantified using the unique, highly polarized angular signature of the sunglint measured over their water surfaces.

The characteristics and performances of a new Mueller-matrix scatterometer will be described. Applications and results on industrial samples will be presented. The device measures the angular distribution of the 16 Mueller-matrix elements, characterizing completely the light polarization modifications induced by any sample, transparent or scattering, in reflexion or in transmission. The measurement is made in less than 1 s., with an accuracy higher than 95 %, for any angle of incidence and any scattering angle in the range ofO° (forward scattering) to 175° (near backscattering). The instrument is using electro-optical polarization modulation techniques for polarization generation, a 4-detector photopolarimeter for polarization detection, and Fast Fourier Transform (FF1') for the analyzis of the 4 signals. The interest of Mueller-matrix analyzis is that, compared to simple scatterometric measurements, this method can give information about the non-ideality of the analyzed samples : shape of the particles in suspensions, multiple reflexions, presence of contaminants, roughness shape of surfaces, porosity, presence of thin surface films. This information is very valuable for complex industrial samples. The applicxations include testing of transparent, non-scattering elements (liquid crystal devices), characterization of scattering translucent samples (suspensions in chemical industries), and inspection of rough surfaces covered or not by thin films (e.g. steel or aluminum sheets on production lines, electrochemical deposits). A future developement of the methjod for imaging Mueller-matrix polanmetry-scatterometry will also be described.

Suspensions of polystyrene latex beads in chiral solutions were investigated. The rotatory power, induced by solubilized sucrose, in near-forward scattering was measured via a method using polarization modulation by photo-elastic modulator. The sensitivity of the measurement was enhanced and optimized in order to measure sucrose concentrations as low as 5 mg/ml in a cell 5 mm thick only. Different concentrations and diameters of latex particles were used in combination with different sucrose concentrations going from 1 mg/ml up to saturation. The experiments showed that the apparent rotatory power is enhanced by multiple scattering, that depolarization effects are less important with highly concentrated sucrose solutions and that attention has to be paid to cell border effects in order to avoid important artifacts, in case of highly scattering suspensions. Qualitative and theoretical explanations of those observations are presented. One possible application of this method is to measure the sugar content in human blood, in vivo, non-invasively, through the skin. The concentration to be evaluated is at the sensitivity limit. So any artifact has to be removed carefully, e.g. skin cell birefringence or chirality.

A parametric analysis of sky radiance and polarization measurements based on a database of calculations indicated that there was information contained in the measurements that was not captured by the data base. We therefore developed an iterative algorithm for retrieving a size distribution and size resolved refractive indices of aerosols from cloud free measurements of polarized sky radiances. Preliminary results indicate that it is possible to retrieve a size resolved refractive index for a wide range of aerosol sizes, as well as an aerosol size distribution.

The absorption of visible light by metal colloids provides beautiful colored glass for aesthetic as well as practical purposes. Since the metal particles dispersed in the colloid have diameters much smaller than the wavelength of light, on the order of 10nm, the elastic scattering cross section is negligible. In typical colloidal solutions the metal particles are approximately spherical and therefore the optical constants are isotropic. Some metal/glass nanocomposites such as RG6 Schott glass contain nonspherical metal particles but the orientation of the particles in the host is random. In order to obtain a polarizing nanocomposite, the nonspherical metal particles must be aligned along a common axis. A fabrication technique based on ultrathin metal deposition has been found to provides the necessary size, shape, and orientation of the metal particles for highly anisotropic optical constants in the visible and near-IR. The measured absorption spectra of the films are analyzed by Maxwell-Garnett theory. The nanocomposite films have extinction coefficients that vary by 2 orders of magnitude depending on the polarization of the incident light. These metal nanocomposite films are useful for micro-optic and waveguide polarizers.

The backscattering Mueller matrices for a range of bead- blasted aluminium samples having a range of surface roughness and slopes are investigated using a 632.8nm linearly polarized HeNe laser. The analyzing polarizing optics and detector are fixed in the backscattering direction and the angle of incidence varied from 0 degrees to 90 degrees. A computer controlled Mueller matrix scatterometer determines the matrix elements. The incident polarization states are set via combinations of a polarizer and waveplates and the backscattered light is Fourier analyzed using a rotating compensator and fixed linear polarizer. The surfaces were characterized using a surface profilometer and the variation of the Mueller matrix elements with incidence angle determined. Only four elements of the normalized Mueller matrix are non-zero. Of these, three vary with incidence angle and the fourth is normalized to unity. A depolarization term P_D calculated from the matrix elements is shown to decrease with increasing angle of incidence. Its value at normal incidence reduces with increasing bead-blast pressure.