High-speed spectral domain OCT at 3600nm

Recent developments of mid-infrared (MIR: >2 microns) OCT, mostly at operating central wavelength around 4 microns have demonstrated the superiority of its penetration depth in materials compared to OCT at 1.3 microns. However, one of the problems with MIR OCT development is the slow speed of data capture and low sensitivity of the images. Here we demonstrate the development of a fast and high sensitivity spectral domain OCT at 3700 nm using a low noise ultra-broadband fs continuum source based on a Cr:ZnS-GaSe and Cr:ZnS-ZGP tandem architecture developed by IPG Photonics and a similar interferometer and spectrometer setup as the 2 micron OCT we developed previously. The axial resolution achieved was 9 microns in air and it takes about 2 mins to capture a volumetric cube at kHz line rate achieving a sensitivity of about 95 dB. The performance of this MIR OCT is compared with our 1960 nm OCT in addition to a commercial 1300 micron OCT on samples from paint to ceramics.