18 February 2011 Improved coupling to integrated spatial heterodyne spectrometers with applications to space
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Multiple Aperture Transform Chip Heterodyne (MATCH) spectrometers have been developed for targeted remote sensing applications in harsh environments. These waveguide-based Fourier Transform Spectrometers (FTS) offer significant improvements in resource efficiency over monolithic glass implementations, but are relatively limited in terms of input coupling efficiency and fill factor of the input facet. Integrated optics spectrometers have significant resource advantages for space applications. Monolithic Spatial Heterodyne Spectrometers are insensitive to vibration and do not require frequent calibration. In addition, Fourier Transform Spectrometers are known to provide significant performance advantages for emission spectroscopy. Ongoing work will improve the MATCH spectrometer input coupling efficiency from free space. This paper discusses the signal to noise improvements expected by incorporation of surface gratings, or back-thinning and stacking of slabs. We show that the use of surface gratings can increase the throughput over coupling to bare waveguides alone (in a single polarization), and provide close to 100% fill factor, albeit with limited field. Étendue improvements associated with stacked slabs are limited only by the sensing area available, but the fill factor of the input facet is limited to ~10%. The impact of these improvements is assessed in the context of two space-based applications: 1) Atmospheric remote sensing in the context of Spatial Heterodyne Observations of Water (solar occultation absorption spectroscopy) near 1.3 μm and 2) Point emission spectroscopy (LIBS/Raman/fluorescence) for mineral identification on a planetary rover.
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A. Scott, P. Bock, C. A. Ramos, B. Lamontagne, P. Cheben, M. Florjańczyk, I. M. Fernandez, S. Janz, A. Ortega-Monux, B. Solheim, D.-X. Xu, "Improved coupling to integrated spatial heterodyne spectrometers with applications to space", Proc. SPIE 7928, Reliability, Packaging, Testing, and Characterization of MEMS/MOEMS and Nanodevices X, 79280K (18 February 2011); doi: 10.1117/12.877208; https://doi.org/10.1117/12.877208

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