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On-chip Fourier transform spectrometer on silicon-on-sapphire

We designed and experimentally demonstrated an on-chip Fourier transform spectrometer on silicon-on-sapphire. The spectrometer comprises an array of twelve Mach–Zehnder interferometers (MZIs) with linearly increasing optical path delays between MZI arms. The propagation loss of 5.2 dB/cm has been experimentally observed for the strip waveguides. The retrieval of an optical spectrum is demonstrated with an inter-band cascade laser centered at 3.3 μm. The resolution is better than 10  cm−1.