Integrated broadband mid-infrared polarization insensitive Fourier-Transform spectrometer

Due to the rotational and vibrational frequency, molecules show unique absorption spectrum in the mid-infrared fingerprint region from 500 to 1500 cm
⁻¹
. Hence, the demonstration of integrated on-chip spectrometers with compact sizes, cost-effective and high performance is important. Here, we demonstrate the first polarization insensitive broadband operational mid infrared spatial heterodyne Fourier-Transform spectrometer (SHFTS) working beyond 5 µm wavelength. A resolution better than 15cm
⁻¹
for both TE/TM polarizations has been experimentally demonstrated in an unprecedented bandwidth of 800 cm
⁻¹
(from 5 µm to 8.5 µm wavelength) for our integrated on-chip SHFTS, using a graded-index Ge-rich SiGe photonics platform.