Quantitative birefringence microscopy with collinearly propagating orthogonally polarized beams.
TL;DR: The proposed technique is aimed towards birefringence measurements in microscopic biological specimens where the magnitude of retardation lies in the range of 0-π radians.
Abstract: Full-field evaluation of spatially varying birefringence is realized by allowing two mutually orthogonally polarized collinearly propagating laser beams to be incident on a birefringent sample. This is achieved by use of a modified Sagnac interferometer. A half-wave plate is placed in the exit path of the interferometer to adjust the polarizations of the incident beams as required. Amplitude components of the light emerging from the birefringent object are then selected and/or combined by a polarizer, and intensities for required orientation of the half-wave plate and the analyzer are digitally recorded. It is shown that a maximum of four frames of intensity data is sufficient for complete evaluation of birefringence. The proposed technique is aimed towards birefringence measurements in microscopic biological specimens where the magnitude of retardation lies in the range of 0-π radians. Simulated and experimental results are presented.
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TL;DR: A scheme to miniaturize a double-channel polarized holographic interferometer optics to create a polarization holographic microscope slide (P-HMS) suitable for integrating with microfluidic lab-on-a-chip (LoC) systems and could play a positive role in promoting the application of birefringence imaging in microfluidity LoC technology.
Abstract: Birefringence is an important optical property of anisotropic materials arising from anisotropies of tissue microstructures. Birefringence parameters have been found to be important to understand optical anisotropic architecture of many materials and polarization imaging has been applied in many researches in the field of biology and medicine. Here, we propose a scheme to miniaturize a double-channel polarization holographic interferometer optics to create a polarization holographic microscope slide (P-HMS) suitable for integrating with microfluidic lab-on-a-chip (LoC) systems. Based on the P-HMS combined with a simple reconstruction algorithm described in the paper, we can not only simultaneously realize holographic imaging of two orthogonal polarization components of dynamic samples in a microfluidic channel but also quantitative measurement of 2D birefringence information, both including the birefringence phase retardation and optic-axis orientation. This chip interferometer allows for off-axis double-channel polarization digital holographic recording using only a single illumination beam without need of any beam splitter or mirror. Its quasi-common path configuration and self-aligned design also make it tolerant to vibrations and misalignment. This work about the P-HMS could play a positive role in promoting the application of birefringence imaging in microfluidic LoC technology.
7 citations
TL;DR: A method for realizing 2D single-shot measurements of birefringence parameters (including both retardation and optic axis orientation) of anisotropic materials using a simple recording setup and an efficient processing algorithm is proposed.
Abstract: A method for realizing 2D single-shot measurements of birefringence parameters (including both retardation and optic axis orientation) of anisotropic materials using a simple recording setup and an efficient processing algorithm is proposed. The recording setup can be built simply by inserting a circular polarizer and a polarization beam splitter, respectively, in the object path and reference path of a conventional off-axis holographic imaging system, with no need for other adjustments. An algorithm for quantitatively retrieving the birefringence parameters from one single-shot hologram is proposed and demonstrated, in which a new quantity describing the birefringence, called complex birefringence parameter, is introduced, and a set of formulas used to extract the birefringence parameters is derived. Some experimental results are given for demonstrating the feasibility of the method that reveal that the method may provide another effective approach for investigating the birefringence properties of dynamic anisotropic materials, especially the birefringence induced by ultrafast pulse lasers.
6 citations
10 Mar 2021
TL;DR: In this article, a non-contact thickness measurement of multi-layer thin films with improving the sensitivity, accuracy, and performance of the measurement techniques is reported, where single and double-layer film thickness measurement using different polarization states were studied.
Abstract: The new scheme of a non-contact thickness measurement of multi-layer thin films with improving the sensitivity, accuracy, and performance of the measurement techniques is reported in this paper. Single- and double-layer film thickness measurement using different polarization states were studied. An alternative architecture using triangular cyclic interferometer with simultaneous measurements of reference and sample arms by splitting the beam at the output of interferometer is mathematically achieved. The polarization phase shift using two steps algorithm is observed, with steps shift of n/2 rad for a double layer sample. This shows that the polarization state has an impact on the thickness measurement of different thin- film materials.
1 citations
TL;DR: In this article , a third angular momentum has been added by twisting the helical path further according to the three-step hierarchical assembly of helical organic nanowires, which converts the dimensionless photon to a hollow spherical photon condensate with interactive dark regions.
Abstract: Photons that acquire orbital angular momentum move in a helical path and are observed as a light ring. During helical motion, if a force is applied perpendicular to the direction of motion, an additional radial angular momentum is introduced, and alternate dark spots appear on the light ring. Here, a third, centrifugal angular momentum has been added by twisting the helical path further according to the three-step hierarchical assembly of helical organic nanowires. Attaining a third angular momentum is the theoretical limit for a photon. The additional angular momentum converts the dimensionless photon to a hollow spherical photon condensate with interactive dark regions. A stream of these photon condensates can interfere like a wave or disintegrate like matter, similar to the behavior of electrons.
TL;DR: In this paper , the Sagnac interferometer was modified with phase shifting approach for the determination of thin-film thickness, and the results showed that the phase-shifting technique using three-polarization settings is more suitable for the thickness measurement of the transparent thin film.
Abstract: This paper presents the comparison of three-, four- and five-step techniques for measuring transparent thin-film thickness of Ta2O5 and WO3 deposited on BK-7 substrates. The Sagnac interferometer was modified with phase shifting approach for the determination of thin-film thickness. The input light beam was split into reference and testing beams. Before the output light reaching the balanced photodetectors, the real-time signal detection was performed to obtain the output intensities of both beams using three-, four-, and five-polarization settings of an analyzer. The thicknesses could then be efficiently translated from the measured intensities. Thicknesses from three-, four- and five-stepping algorithms were compared with ones from the conventional FE-SEM measurement, and it was discovered that the former performed better with less errors. The findings show that the phase-shifting technique using three-polarization settings is more suitable for the thickness measurement of the transparent thin film.