access icon free Adaptive etalon suppression technique for long-term stability improvement in high index contrast waveguide-based laser absorption spectrometers

The authors present an adaptive algorithm based on a non-linear regression model for mitigating time-varying etalon drifts in line-scanned optical absorption spectrometers. By dynamically varying the etalon spectral background using physically realistic degrees of freedom, the authors’ dynamic etalon fitting-routine (DEF-R) significantly increases the spectral baseline recalibration interval as compared to conventional fringe subtraction models. They provide an empirical demonstration of the efficacy of DEF-R using an on-chip 10 cm silicon waveguide for near-infrared methane absorption spectroscopy at 6057 cm−1, which suffers significant etalon spectral noise due to reflections and multi-path interference from stochastic line-edge roughness imperfections. They demonstrate the corresponding improvement in both spectral clean-up and long-term stability via Allan-variance analysis. For the sensor presented here, application of DEF-R enables Gaussian-noise limited performance for more than 102 s and provides almost an order-of-magnitude improvement in stability time with respect to conventional baseline subtraction. Although DEF-R is applied here to an on-chip sensor embodiment, they envision their technique to be applicable to any absorption sensor limited by time-varying etalon drifts.

Inspec keywords: optical sensors; statistical analysis; regression analysis; silicon; chemical sensors; laser noise; infrared detectors; elemental semiconductors; light interference; light reflection; optical waveguides; organic compounds; light interferometry; infrared spectra; photodetectors; measurement by laser beam; adaptive optics

Other keywords: nonlinear regression model; dynamic etalon fitting-routine; Gaussian-noise limited performance; absorption sensor; time-varying etalon drifts; high index contrast waveguide-based laser absorption spectrometers; size 10.0 cm; fringe subtraction models; spectral baseline recalibration interval; light reflections; etalon spectral background; near-infrared methane absorption spectroscopy; on-chip sensor embodiment; stochastic line-edge roughness imperfections; long-term stability improvement; on-chip silicon waveguide; Si; adaptive etalon suppression technique; Allan-variance analysis; line-scanned optical absorption spectrometers

Subjects: Chemical sensors; Optical waveguides; Detection of radiation (bolometers, photoelectric cells, i.r. and submillimetre waves detection); Metrological applications of lasers; Optical interferometry; Optical interference and speckle; Chemical sensors; Elemental semiconductors; Metrological applications of lasers; Edge and boundary effects; optical reflection and refraction; Photodetectors; Optical waveguides and couplers

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Correspondence
This article has following corresponding article(s):
suppressing elaton drifts