Sixteen-beam grating-based division-of-amplitude photopolarimeter

Superachromatic polarization modulator for stable and complete polarization measurement over an ultra-wide spectral range

The polarization measurement system deals with polarized light-matter interactions, and has been a kind of powerful optical metrology applied in wide fields of physics and material. In this paper, we address several general theoretical aspects related to the system model and optimization for linear polarization systems from a view of the matrix algebra. Based on these theories, we propose a new framework of superachromatic polarization modulator (PM) by combining a linear polarizer and a sequence of parallel linear retarders (LRs) for a typical kind of linear polarization system based on the rotating compensator (RC) principle. In the proposed PM, the LRs are made of quarter-wave plates and as a whole act as the RC. Compared with conventional achromatic/superachromatic composite waveplates, the LR sequence has general axis orientations and is optimized by the condition number of the instrument matrix of the PM, which thereby provide much more flexibility to achieve uniform, stable and complete polarization modulation over ultra-wide spectral range. The intrinsic mechanisms, including the working principle, optimization strategy and in-situ calibration method of the proposed PM, are presented and revealed mathematically by the matrix algebra. Results on several prototypes of the PM demonstrate the validity and capability of the proposed methods for applications in broadband polarization measurement systems. The fabricated PM is further applied to a home-made dual RC Mueller matrix ellipsometer, and the accuracy and precision in the full Mueller matrix measurement are better than 2‰ and 0.6‰ respectively over the ultra-wide spectral range of 200∼1000 nm. Compared with existing techniques, the proposed PM has advantages due to superachromatic performances over ultra-wide spectral ranges, stable and complete modulation of the polarized light, and convenience for adjustment and calibration.

Matrix Fourier optics enables a compact full-Stokes polarization camera

Recent developments have enabled the practical realization of optical elements in which the polarization of light may vary spatially. We present an extension of Fourier optics-matrix Fourier optics-for understanding these devices and apply it to the design and realization of metasurface gratings implementing arbitrary, parallel polarization analysis. We show how these gratings enable a compact, full-Stokes polarization camera without standard polarization optics. Our single-shot polarization camera requires no moving parts, specially patterned pixels, or conventional polarization optics and may enable the widespread adoption of polarization imaging in machine vision, remote sensing, and other areas.

Polarization state generation and measurement with a single metasurface

The constituent elements of metasurfaces may be designed with explicit polarization dependence, making metasurfaces a fascinating platform for new polarization optics. In this work we show that a metasurface grating can be designed to produce arbitrarily specified polarization states on a set of defined diffraction orders given that the polarization of the incident beam is known. We also demonstrate that, when used in a reverse configuration, the same grating may be used as a parallel snapshot polarimeter, requiring a minimum of bulk polarization optics. We demonstrate its use in measuring partially polarized light, and show that it performs favorably in comparison to a commercial polarimeter. This work is of consequence in any application requiring lightweight, compact, and low-cost polarization optics, polarimetry, or polarization imaging.

Axially resolved complete mueller matrix confocal microscopy

We introduce a technique that is capable of obtaining complete polarization-sensitive three-dimensional images that could reveal unknown anatomical conditions of living tissue that possess polarization-dependent signatures. Previously, the 16 Mueller coefficients were measured independently only by use of two-dimensional imaging techniques. We also present the experimental combination of a depth-resolved confocal imaging system with a complete Mueller matrix polarimeter. To calibrate the system, a double-pass method had to be implemented. We also indicate, experimentally, that the confocal sectioning of the system has a degrading effect on axially resolved Mueller matrix measurements.

Spectral polarization measurements by use of the grating division-of-amplitude photopolarimeter

The grating division-of-amplitude photopolarimeter (G-DOAP) is an instrument that exploits the multiple-beam-splitting, polarizing, and dispersive properties of diffraction gratings for the time-resolved measurement of the complete state of polarization of collimated broadband incident light, as represented by the four Stokes parameters as a function of wavelength across the spectrum. It is a compact, high-speed sensor that has no moving parts and is simple to install and operate. These characteristics make the G-DOAP well suited for in situ spectroscopic ellipsometry (SE) applications for monitoring and controlling thin-film processes. The design and performance of a prototype instrument are presented. Precise SE measurements, to +/-0.04 degrees in psi and +/-0.1 degrees in delta, are demonstrated in the 550-940-nm wavelength range.

General and self-consistent method for the calibration of polarization modulators, polarimeters, and mueller-matrix ellipsometers

Calibration of polarization-state generators (PSG's), polarimeters, and Mueller-matrix ellipsometers (MME's) is an important factor in the practical use of these instruments. A new general procedure, the eigenvalue calibration method (ECM), is presented. It can calibrate any complete MME consisting of a PSG and a polarimeter that generate and measure, respectively, all the states of polarization of light. In the ECM, the PSG and the polarimeter are described by two 4 x 4 matrices W and A, and their 32 coefficients are determined from three or four measurements performed on reference samples. Those references are smooth isotropic samples and perfect linear polarizers. Their optical characteristics are unambiguously determined during the calibration from the eigenvalues of the measured matrices. The ECM does not require accurate alignment of the various optical elements and does not involve any first-order approximation. The ECM also displays an efficient error control capability that can be used to improve the MME behavior. The ECM is illustrated by an experimental calibration, at two wavelengths (458 and 633 nm), of a MME consisting of a coupled phase modulator associated with a prism division-of-amplitude polarimeter.