Design and Test of a Slab Waveguide Spectrometer for Spatial Heterodyne Observations of Water Vapor
Sinclair, Kenneth Allan
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The Slab Waveguide Interferometric Spatial Heterodyne (SWISH) Spectrometer was designed as a high-resolution instrument designed to demonstrate the ability of slab waveguide spatial heterodyne spectrometer technology through measurements of water vapor in Earth’s atmosphere. It is based on a multiaperture Fourier-transform planar waveguide spectrometer. The Fourier technique was used for spectra retrieval. The absorption signal will be measured with a spectral range of 2.5 nm centered in the near infrared spectral region on the 1.3645 μm wavelength with a spectral resolution of 0.05 nm. The resolution of the interferometer array is designed so that errors in the retrieved spectrum, measured using the least squares method, are minimized. The slab waveguide itself was constructed such that the interferometers and monitoring waveguides have an output pitch, which matches that of the linear detector array. It was designed for the 1.3645 μm wavelength range using a 1.3 μm wide and 0.75 μm high silicon-on-insulator (SOI) ridge waveguides and contained 100 Mach-Zehnder interferometers along with 11 'pass-through' waveguide. This thesis spans several components of the project relating to the development and testing of the SWISH Spectrometer. These parts include: (1) developing and building a prototype slab waveguide spatial heterodyne spectrometer (SWSHS) chip and breadboard optical instrument at spatial heterodyne observations of water (SHOW) wavelengths; (2) investigating alternative method(s) for increased coupling efficiency; (3) assembling a prototype spectrometer for SHOW waveband; (4) assembling input optics for the SWSHS; (5) developing system packaging and build a prototype system; (6) developing inversion algorithms and calibration procedures for system using test data from laboratory tests of micro-SHOW linear prototype.