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Acoustically Controlled All-Fiber Lasers
Published in Iniewski Krzysztof, Integrated Microsystems, 2017
Christian Cuadrado-Laborde, Antonio Diez, José L. Cruz, Miguel V. Andrés
Brillouin scattering essentially refers to the scattering of a light wave by an acoustic wave [25]. When a coherent pulse of light propagates through a medium, part of its energy is backscattered due to a nonelastic interaction with the acoustic phonons. This backscattered light is composed of a frequency downshifted Stokes light and an upshifted anti-Stokes light, whose spectral positions are dependent on temperature and strain environment of the fiber, in this way allowing its use as a sensing mechanism [25–30]. Fiber optics distributed temperature, and/or strain, sensors have becoming very attractive for applications requiring sensing lengths of many kilometers, principally due to their inexpensiveness and availability. Optical fiber-based distributed sensor systems normally make use of the principle of optical time-domain reflectometry [27,28,31]. Therefore, an optical pulse is launched into one end of the fiber system and the variation of the scattered light is detected as a function of time, giving in this way information about the temperature or strain as a function of distance. A key requirement in this measurement system is a stable light source with a narrow enough spectral linewidth [27]. In addition, for time-domain reflectometry applications, the sensor spatial resolution proportionally depends on the optical pulse width and so it must also be considered [28]. In order to fulfill all these requirements, solid state lasers with external cavities—plus amplifiers and amplitude modulators—are currently used in these systems [27]. Here we propose using this compact all-fiber pulsed light source as a relatively simpler alternative.
Corneal Biomechanics Losses Caused by Refractive Surgery
Published in Current Eye Research, 2023
FangJun Bao, Bernardo T. Lopes, XiaoBo Zheng, YuXin Ji, JunJie Wang, Ahmed Elsheikh
In addition to ORA and Corvis ST, currently the only clinically available devices to provide in vivo corneal biomechanical measures, other technologies based on lower-magnitude or non- perturbation techniques such as Brillouin scattering, OCE and HFU are under development. Brillouin microscopy (BM) could map the spatial biomechanical state of the cornea through analyzing the inelastic scattering of light when it interacts with microscopic sound waves. Further, the regional resolving capability of BM has enabled a more comprehensive evaluation of corneal cross-linking (CXL) procedures in stiffening the cornea.51–57 However, determining material parameters (e.g. elastic modulus) from the Brillouin frequency shift is still an open question.58 Moreover, influence of water content, high acquisition time and cost have limited the commercialization process of BM.59,60