Swept-source OCT using pulsed mid-infrared light

摘要

A swept-source optical coherence tomography (OCT) system using mid-infrared light is demonstrated usingcommercially available light source and photodetectors. The light source is a tunable external cavity quantum cascadelaser (QCL) with four laser modules and a wavelength range of 5.4μm – 12.8μm. The laser output is pulsed and has amaximum allowable duty cycle of 8%. A thermoelectrically cooled photovoltaic detector with a peak sensitivity at 8μmis configured in a Michelson interferometer setup. Noise from three sources are characterized: the analogue-to-digitalconverter (ADC), the detectors and the relative intensity noise (RIN). The ADC and the detector have a noise spectraldensity of 2.8 pW/√Hz and 21.4 pW/√Hz over a bandwidth of 100 MHz respectively; the value of RIN is -102 dB/Hz.The OCT system is used to collect the reflectivity profile of a mirror, which is measured with a signal to noise ratio(SNR) of 17.5 dB. Decreasing the time of sweep from 1s to 200ms has the effect of reducing the SNR by 4 dB.