Achromatic Savart polariscope: choice of materials

Mu, Tingkui; Zhang, Chunmin; Li, Qiwei; Zhang, Lin; Wei, Yadong; Chen, Qingying

doi:10.1364/oe.22.005043

Cited by 18 publications

(7 citation statements)

References 24 publications

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“…Here the the 1/λ response is dominant, in full agreement with Eq. (4), because in this spectral range the chromatic variation of calcite's birefringence -and therefore, of the beam separation d -is not significant [25].…”

Section: Calibration and Evaluation Of Coherencementioning

confidence: 99%

Snapshot circular dichroism measurements

Arteaga¹,

Ossikovski²

2019

Opt. Express

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Two coherent waves carrying orthogonal polarizations do not interfere when they superpose, but an interference pattern is generated when the two waves share a common polarization. This well-known principle of coherence and polarization is exploited for the experimental demonstration of a novel method for performing circular dichroism measurements whereby the visibility of the interference fringes is proportional to the circular dichroism of the sample. Our proof-of-concept experiment is based upon an analog of Young's double-slit experiment that continuously modulates the polarization of the probing beam in space, unlike the time modulation used in common circular dichroism measurement techniques. The method demonstrates an accurate and sensitive circular dichroism measurement from a single camera snapshot, making it compatible with real-time spectroscopy. IntroductionCircular dichroism (CD) is the differential absorption of circularly polarized light. Despite this differential absorption being typically very small in optically active enantiomers (10 −5 -10 −4 ), CD spectroscopy has become a well-established technique, especially as a method for identifying structural motifs in chiral proteins [1]. Due to its intrinsic weakness, the detection of CD requires relatively complex and expensive instruments that often need to integrate the low signal over significant measurement time.Modern approaches to CD measurement are based on a polarization-modulation scheme in which linearly polarized probing light passes through a quartz crystal that has been subjected to periodic time-varying mechanical stress inducing birefringence due to the photoelastic effect. The modulation device, commonly called photoelastic modulator, produces circular polarizations with alternating handedness in time [2]. In the early realizations of spectroscopic CD measurements from 1960's [3], the polarization modulation was also accomplished with electrically driven Pockels cells, but nowadays virtually all commercial CD instruments use photoelastic modulators. Regardless whether Pockels cells or photolastic modulators are used as polarization-modulation elements, the measurement approach based on the analysis of the temporal variation of the polarization of the modulated probing light is the same.In this work we present a novel method for spectroscopic CD characterization that is based on spatial rather than on temporal polarization modulation. The application of multi-domain spatial, spectral, angular, etc modulation approaches has been previously explored by Tyo and coworkers in the more general context of polarimetry [4,5]. In our method, different points of the sample are illuminated with different, well-controlled states of polarization with alternating handedness. The presence of CD in the sample results in the formation of a periodic interference pattern at the detector. As chiroptical data are obtained from the analysis of a single snapshot of the interference pattern, the novel approach is not subject to measurement time constraints typi...

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Section: Calibration and Evaluation Of Coherencementioning

confidence: 99%

Snapshot circular dichroism measurements

Arteaga¹,

Ossikovski²

2019

Opt. Express

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“…The OPD is eliminated as both the polarization components go through a displacement and a stationary process. Note that l is still dependent on λ due to dispersion, which can be solved by using two materials to make SP itself roughly achromatic [19]. Then, the QWP should be replaced by an achromatic light retarder.…”

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confidence: 99%

Toward practical weak measurement wavefront sensing: spatial resolution and achromatism

et al. 2022

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The weak measurement wavefront sensor detects the phase gradient of light like the Shack–Hartmann sensor does. However, the use of one thin birefringent crystal to displace light beams results in a wavelength-dependent phase difference between the two polarization components, which limits the practical application. Use of a Savart plate, which consists of two such crystals, can compensate for the phase difference and realize achromatic wavefront sensing when combined with an achromatic retarder. We discuss the spatial resolution of the sensor and experimentally reconstruct a wavefront modulated by a pattern. Then we obtain the Zernike coefficients with three different wavelengths before and after modulation. Our work makes this new wavefront sensor more applicable to actual tasks like biomedical imaging.

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“…In the last few years, birefringent interferometers have attracted particular attention because of their compactness and insensitivity to vibrations, due to their common-path nature. They are mostly based on Wollaston or Savart prisms [26,27], or their variants [28]; because of the arrangement of their optical axes, they are characterized by a strong chromatic lateral displacement, which reduces the visibility of the interference fringes [29].…”

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confidence: 99%

Hyperspectral imaging with a TWINS birefringent interferometer

Perri¹,

Faria²,

Teles-Ferreira³

et al. 2019

Opt. Express

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We introduce a high-performance hyperspectral camera based on the Fouriertransform approach, where the two delayed images are generated by the Translating-Wedge-Based Identical Pulses eNcoding System (TWINS) [Opt. Lett. 37, 3027 (2012)], a commonpath birefringent interferometer that combines compactness, intrinsic interferometric delay precision, long-term stability and insensitivity to vibrations. In our imaging system, TWINS is employed as a time-scanning interferometer and generates high-contrast interferograms at the single-pixel level. The camera exhibits high throughput and provides hyperspectral images with spectral background level of −30dB and resolution of 3 THz in the visible spectral range. We show high-quality spectral measurements of absolute reflectance, fluorescence and transmission of artistic objects with various lateral sizes.

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Achromatic Savart polariscope: choice of materials

Cited by 18 publications

References 24 publications

Snapshot circular dichroism measurements

Snapshot circular dichroism measurements

Toward practical weak measurement wavefront sensing: spatial resolution and achromatism

Hyperspectral imaging with a TWINS birefringent interferometer

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