Principles and Design of a Planar Waveguide Fourier Transform Spectrometer for Remote-Sensing Applications

This paper presents the design and operating principles of an advanced Fourier transform (FT) microspectrometer. The microspectrometer is a static Fourier transform instrument based on the principle of spatial heterodyne spectroscopy (SHS), affording high optical throughput (étendue) as compared with an arrayed waveguide (AWG) or planar waveguide echelle grating spectrometer. The instrument is realized as a densely-packed array of Mach-Zehnder interferometers (MZIs) with linearly increasing optical path delays (OPDs). Each MZI in the array constitutes a sampling point in the discrete Fourier-transform of the optical spectrum. The use of discrete MZIs in this device makes the selection of Fourier samples straightforward, and the throughput advantage permits the development of very high-resolution devices.