28 October 2015 Volume refractometry of liquids using stable optofluidic Fabry–Pérot resonator with curved surfaces
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This work reports a simple, miniaturized optical sensing module for liquid refractometry. It is based on a stable Fabry–Pérot resonator consisting of two silicon cylindrical mirrors with a cylindrical lens in between. The lens is formed by a capillary tube through which the analyte passes. This setup enables volume refractometry, where light propagates through the sample realizing high-interaction depth. The cylindrical surfaces achieve light confinement, reducing the light escaping loss encountered in classical cavities with straight mirrors; hence, a high-quality factor (Q) over 1000 is attained. Exploiting this high Q, we adopt the refractive index (RI) measurement criterion: operating at a fixed wavelength and detecting the power drop as a consequence to the spectral shift with RI change. This technique showed that measuring RI change Δn above the RI of the reference solution can be determined for 0.0023<Δn<0.0045. Sensitivity up to 4094  dBm/RIU is achieved. A wider range is still achievable by the conventional method of tracing the shift in peak wavelengths: a range of Δn=0.0163  RIU can be scanned, with a sensitivity of 221  nm/RIU. Error analysis has been accomplished, and the device’s design parameters are discussed to evaluate the performance.
© 2015 Society of Photo-Optical Instrumentation Engineers (SPIE)
Noha Ali Aboulela Gaber, Yuto Takemura, Frédéric Marty, Diaa A. M. Khalil, Dan Angelescu, Elodie Richalot, Tarik Bourouina, "Volume refractometry of liquids using stable optofluidic Fabry–Pérot resonator with curved surfaces," Journal of Micro/Nanolithography, MEMS, and MOEMS 14(4), 045501 (28 October 2015). https://doi.org/10.1117/1.JMM.14.4.045501 . Submission:

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