Wide tuning range wavelength-swept laser with single semiconductor optical amplifier for OCT

Abstract

This paper reports on a wide-range, high-speed, wavelength-swept laser operating at 1310nm for optical coherence tomography (OCT) applications. The laser comprises a pigtailed wideband, high-gain semiconductor optical amplifier (SOA) and a wavelength-scanning filter in a fiber ring cavity configuration. The tunable filter consists of a diffraction grating and polygon mirror scanner in Littrow configuration. A photodiode is used to generate a start trigger signal synchronized to start of each frequency sweep. Intracavity prisms are aligned to provide constant and narrow laser linewidth and linear frequency sweep. This arrangement also generates a wide tuning range for a given beam deflection angle by the polygon scanner while maintaining narrow laser linewidth. The laser exhibits a peak power of 20mW. The measured tuning range of the laser is 170nm maximum, with 160nm FWHM at a scanning frequency of 20kHz using a single custom engineered SOA device. Laser output is coupled via HI1060 fiber with a cut-off wavelength of 980nm ensuring single-mode propagation over the 1230nm to 1400 nm tuning range.