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An approach is proposed to implement diffractive optical elements for the conversion of the polarization state of beams. Calcite crystal etching technology is developed and applied to manufacture a four-sector polarization converter. The fabricated four-sector polarization converter is experimentally investigated. The orthogonal polarization state of beams in opposite sectors is achieved by selecting a wavelength with a tunable laser. The experimental results of focusing the converted beams are consistent with the numerical simulation.
A holographic projection system based on the encoding of computer-generated holograms onto a spatial light modulator is discussed. We show how the size, location, and polarization state of the output can be controlled completely electronically, without physically moving any element in the system. It is finally shown that the system is capable to produce optical logical operations by superimposing two different images encoded onto orthogonal polarization states. We show how these images can be added or subtracted, giving a polarization-based logic system. Experimental results are included in all cases.
We experimentally demonstrate an iterative method for a vectorial optical field generator (VOF-Gen) to achieve accurate amplitude modulation in creating arbitrary complex beams. The method could converge rapidly in several steps and is effective to optimize the patterns applied to the liquid crystal spatial light modulators on a pixel-by-pixel basis to obtain arbitrary desired amplitude distribution. Meanwhile, this method could also mitigate the speckles caused by the defects of the optical components used in the VOF-Gen system and calibrate the wavefront related to the amplitude distribution. Several kinds of optical fields with different intensity distributions are successfully generated to verify the capability and versatility of the presented technique. This effective method may find many important applications in optical tweezers, microscopy, and unidirectional coupling.
Hypernumerical aperture and polarized illumination are the key technologies of resolution enhancement of lithography. When the numerical aperture reaches 0.85 and above, especially in the immersion lithography, polarization effect must be taken into consideration. The performance of the projection lens needs to be characterized by rigorous polarization aberration. The vector polarization imaging system that is suitable for hypernumerical aperture is established, and the distortion effects introduced by polarization aberration are analyzed. Orientation Zernike polynomials-based method and Pauli–Zernike polynomials-based method are adopted to parameterize the polarization aberration represented by Jones pupil. Critical dimension error, placement error, and normal int. log slope index are introduced as the index to value imaging distortion. The proposed method and analysis conclusion would provide meaningful guidance for projection lens design of lithographic tools.
Retarders or waveplates are tools for polarization modification in bulk optical systems. These devices usually have a strong wavelength dependence in their performance, making them suitable for use over a wavelength band on the order of a few percent of the center wavelength for which they are made. Display and tunable laser applications are examples that can require consistent polarization modification over a much broader wavelength range. We discuss new methods and designs for dramatically increasing range of performance and review older methods as well. We show examples of achievable performance using modern polymer and liquid crystal materials.
We report an in-depth experimental characterization and analysis of an infrared active polarimetric imaging system based on the orthogonality breaking polarization-sensing approach. We first recall the principle of this laser scanning polarimetric imaging technique, based on the illumination of a scene by means of a dual-frequency dual-polarization light source. The experimental design is then described, along with measurements on test scenes with known polarimetric properties used to validate/calibrate the imaging system and to characterize its optical properties (sensitivity and resolution). The noise sources that temporally and spatially affect the quality of the orthogonality breaking data are then investigated. Our results show that the raw temporal signals detected at a given location of the scene are perturbed by Gaussian fluctuations, and the spatial information contained in the images acquired through raster scan of the scene are dominated by speckle noise, which is a common characteristic of active polarimetric imaging systems. Finally, the influence of the source temporal coherence on the images is analyzed experimentally, showing that orthogonality breaking acquisitions can still be performed efficiently with a low-coherence source.
We provide a method for calibrating microgrid polarization cameras that is simpler and easier to set up than existing methods. Applying this method to three different commercially available cameras, we compare the mean values and variances in their diattenuation and orientation properties. We derive formulas giving the accuracy with which the pixel polarization properties can be calibrated in both the Gaussian and Poisson noise regimes and demonstrate the statistical instability of the extinction ratio as a parameter. In a series of calibration measurements, we estimate the pixel-to-pixel variation of polarization properties and show how to separate the effects of temporal noise from manufacturing variation.
We describe a numerical method for obtaining a nondepolarizing estimate from an experimental Mueller matrix, a necessary preliminary step in determining the Jones matrix and the polarization properties of the sample under study. The proposed method, being a variant of the general virtual experiment approach, is based on minimizing the least squares distance between the light intensities virtually generated by the effectively measured Mueller matrix of the sample and by its nondepolarizing estimate, while taking into account the exact phenomenological description of the polarimetric instrument used. It can be applied to complete, as well as to partial (12-element) experimental Mueller matrices. The application of the method is illustrated on experimental examples and its performance is compared to that of alternative approaches.
Optimization of polarimeters has historically been achieved using an assortment of performance metrics. Selection of an optimization parameter is, however, frequently made on an ad hoc basis. We rigorously demonstrate that optimization strategies in Stokes polarimetry based on three common metrics, namely the Frobenius condition number of the instrument matrix, the determinant of the associated Gram matrix, or the equally weighted variance, are frequently formally equivalent. In particular, using each metric, we derive the same set of constraints on the measurement states, correcting a previously reported proof, and show that these can be satisfied using spherical 2 designs. Discussion of scenarios in which equivalence between the metrics breaks down is also given. Our conclusions are equally applicable to optimization of the illumination states in Mueller matrix polarimetry.
A quantum LIDAR for improving resolution using quantum entanglement in the polarization degree of freedom is described. A thorough mathematical analysis of this device is provided. A mathematical discussion of how to generate other more robust entangled states is developed. Internal loss within the entanglement generator and external loss due to atmosphere, detectors, and targets are modeled. A method using these approaches for imaging is provided giving N times classical resolution, where N is the number of photons entangled with explicit results exhibited for N = 3. Closed form expressions for the wave function, normalization, density matrix, reduced density matrix, visibility, and probabilities of detection of one through three photons using detectors with general polarization characteristics are provided. An explicit entanglement generator and detector designs are provided in terms of linear and nonlinear photonics devices. The fundamental role of postselection measurement for generating entanglement is included. Discussions of entanglement devices that will produce general M&M states at near-visible frequencies are given. A discussion of a bearing measurement device that exhibits both super sensitivity and resolution is provided. Computational results are provided that compare probabilities of detection for three single photon detectors with −45-deg, 45-deg, and 45-deg linear polarization. Results for detecting one to three photons or the vacuum state are compared. Computational results for detecting three photons with these detectors for various values of internal and atmospheric loss are provided. Resolution improvements born of quantum entanglement are shown not to degrade with loss. Loss degrades probability of detection not resolution.
In polarimetric instruments, it is often necessary to characterize the polarimetric dependence at various polarization states. Frequently, this is done by placing a polarizer between the instrument and light source. Certain polarizer materials (e.g., wire grids as opposed to polymer-based materials) tend to reflect a significant amount of light, which can cause second-order reflections in the region between the two polarizers. We characterize the reflections using Jones calculus and discuss their significance for polarization instruments.
We describe a method of tracing a backward (from camera) ray in a scene that contains birefrigent (uniaxial) media. The physics of scattering of an electromagnetic wave by a boundary between two media is well known and is a base for ray tracing methods; but processing of a backward ray differs from scattering of a “natural” forward ray. Say, when a backward ray refracts by a boundary, besides the energy transfer coefficient like for a forward ray, one must account for the radiance change due to beam divergence. We calculate this factor and prove it must be evaluated only for the first and the last media along the ray path while the contributions from the intermediate media mutually cancel. We present a closed numerical method that allows one to perform transformation of a backward ray on a boundary between two media either of which can be birefrigent. We hope it is more convenient and ready for usage in ray tracing engines than known publications. Calculation utilizes Helmholtz reciprocity to calculate directions of scattered rays and their polarization (i.e., Mueller matrices), which is advantageous over a straightforward “reverse” of forward ray transformation. The algorithm was integrated in the lighting simulation system Lumicept and allowed for an efficient calculation of images of scenes with crystal elements.
Collected sources for the different types of visualizations used in the field of polarization imaging are not extensive. Here, we survey and review the different visualization techniques in passive polarimetric imaging. Analysis of the methods is done by applying various concepts from the field of visualization. We provide recommendations for choosing a visualization based on the data structure, spatial frequency, and analysis goals.
We present the results of the first quantitative multimodal confocal imaging study of methylene blue (MB)-stained cancer and normal human renal cells obtained from fine needle aspiration (FNA) biopsies. Fluorescence emission images provided morphological assessment, and fluorescence polarization (Fpol) images yielded quantitative characterization of each cell in the investigated samples. FNA specimens are obtained from discarded malignant and normal renal specimens following surgery. Prior to imaging, the cells are stained in aqueous MB solution. Our results demonstrate that all the specimens investigated are heterogeneous in terms of size and exhibited Fpol. Cancerous specimens predominantly contain cells of larger size that exhibit higher Fpol as compared to normal specimens. Imaging results correlated well with clinical assessment of the samples. Our results suggest that morphological assessment using fluorescence emission imaging and quantitative information provided by Fpol imaging may be valuable in determining the presence or absence of renal cancer cells in FNA specimens.