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Open AccessArticle

Two-Dimensional Digital Beam Steering Based on Liquid Crystal Phase Gratings

by Mario García de Blas, Morten Andreas Geday, Jose Manuel Otón and Xabier Quintana Arregui

Appl. Sci. 2021, 11(8), 3632; https://doi.org/10.3390/app11083632 - 17 Apr 2021

Cited by 13 | Viewed by 5303

Electrically tunable phase gratings are able to steer an incoming light beam without employing movable parts. Here, we present the design and implementation of a 2D beam steering device by cascading two orthogonal 1D liquid crystal (LC) based phase gratings, each having an array of 72 rectangular individually controlled pixels and driven by a custom 12-bit Pulse-Width Modulation (PWM) electrical driver. High-resolution structures in glass wafers coated with transparent Indium-Tin Oxide (ITO) have been prepared using Direct Laser Writing (DLW) techniques. With DLW, a high number of pixels can easily be drawn with an interpixel space of less than 3 μm, leading to devices with a high fill factor. The active area of the cascaded device is 1.1 × 1.1 mm². We present a 72 × 72 point efficiency map corresponding to a maximum diagonal steering angle of 1.65°. Special attention has been paid to make the device compatible with space application by avoiding electronics in the active area. Full article

(This article belongs to the Collection Optical Design and Engineering)

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11 pages, 5276 KB

Open AccessLetter

A Compact Mid-Infrared Spectroscopy System for Healthcare Applications Based on a Wavelength-Swept, Pulsed Quantum Cascade Laser

by Takuya Koyama, Naoto Shibata, Saiko Kino, Atsushi Sugiyama, Naota Akikusa and Yuji Matsuura

Sensors 2020, 20(12), 3438; https://doi.org/10.3390/s20123438 - 18 Jun 2020

Cited by 25 | Viewed by 5037

Abstract

A mid-infrared spectroscopic system using a high-speed wavelength-swept and pulsed quantum cascade laser (QCL) for healthcare applications such as blood glucose measurement is proposed. We developed an attenuated total reflection measurement system comprising the QCL with a micro-electromechanical system (MEMS)-scanning grating, hollow optical fibers, and InAsSb detector and tested its feasibility for healthcare applications. A continuous spectrum was obtained by integrating comb-shaped spectra, the timing of which was slightly shifted. As this method does not require complex calculations, absorption spectra are obtained in real-time. We found that the signal-to-noise ratio of the obtained spectrum had been improved by increasing the number of spectra that were integrated into the spectrum calculation. Accordingly, we succeeded in measuring the absorption spectrum of a 0.1% aqueous glucose solution. Furthermore, the absorption spectra of human lips were measured, and it was shown that estimation of blood glucose levels were possible using a model equation derived using a partial least squares regression analysis of the measured absorption spectra. The spectroscopic system based on the QCL with MEMS-scanning grating has the advantages of compactness and low cost over conventional Fourier transform infrared-based systems and common spectroscopic systems with a tunable QCL that has a relatively large, movable grating. Full article

(This article belongs to the Special Issue Optical and Photonic Sensors for Biomedical Applications: Advances and Emerging Solutions)

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15 pages, 5935 KB

Open AccessArticle

An Exact Analytical Solution for Thermoelastic Response of Clamped Beams Subjected to a Movable Laser Pulse

by Xianfeng Yang, Jingxuan Ma, Shoubin Liu, Yun Xing, Jialing Yang and Yuxin Sun

Symmetry 2018, 10(5), 139; https://doi.org/10.3390/sym10050139 - 1 May 2018

Cited by 7 | Viewed by 3676

Abstract

The thermoelastic dynamic response of a clamped Bernoulli beam was studied when it was irradiated by a movable, temporally non-Gaussian, laser pulse. Both the energy absorption depth and the time decaying effects were considered. The temperature distribution, deflection, vibration acceleration, and stress of the beam were derived analytically, and the variations of them with time and space were illustrated. It was shown that the vibration frequency is independent of the scanning speed of the laser pulse. It is important to notice that, although the deflection of the beam is small, high vibration acceleration can be induced in microbeams, which is important for failure and fracture of the beam. Moreover, compressive stress is induced in the beam, but the importance of temperature-induced stress and deformation-induced stress may be different according to the duration time and moving speed of the laser pulse. Full article

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