Mid-infrared spectroscopy in the 2-4 μm wavelength range is of cardinal value for many sensing applications. Current solutions involve bulky and expensive systems to operate. Silicon-on-Insulator (SOI) waveguide technology offers means to miniaturize the different parts of the spectrometer. However, the
development of on-chip detectors for the mid-infrared wavelength range is in its infancy and the characteristics are not on par with their discrete (cooled) counterparts. In this work, a compact and cheap mid-infrared spectrometer is realized by integrating a SOI Arrayed Waveguide Grating (AWG) spectrometer operating in the 2.3 μm wavelength range with a high performance mid-infrared photodiode. The AWG has twelve output channels with a spacing of 225 GHz (4 nm) and a free spectral range (FSR) of 3150 GHz (56 nm), which are simultaneously collected by a
single, transistor outline (TO)-packaged extended InGaAs PIN photodiode. The response of each AWG channel is discerned by time-sequentially modulating the optical power in each output channel using integrated Mach-Zehnder based (MZI) thermo-optic modulators with a pi-phase shift power consumption of 50 mW. As an example, the absorption spectrum of a 0.5 mm thick polydimethylsiloxane sheet (PDMS) is sampled and compared to a benchtop spectrometer to good agreement.
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