High-speed wavelength-swept laser source with high-linearity sweep for optical coherence tomography

This paper reports on a high-speed, wide-range, wavelength-swept laser operating at 1310 nm with highly linear sweep performance for optical coherence tomography (OCT) applications. The simple and robust laser comprises a pigtailed semiconductor optical amplifier and a wavelength-scanning filter in an extended fiber cavity configuration. The tunable filter consists of a diffraction grating and polygon mirror scanner. A photodiode is used to generate a start trigger signal synchronized to start of each frequency sweep. Intracavity prism beam expanders are aligned to provide constant laser linewidth and linear frequency sweep. The laser exhibits a peak power of 15 mW. The tuning range of the laser is 117 nm maximum, and 100 nm full-width at half-maximum at a scanning frequency of 20 kHz. OCT signal in time-constant fast Fourier transform mode is compared with OCT signal using conventional wavelength rescaled processing. Coherence length was measured to be 5 mm. This approach realizes a practical and robust laser system suitable for deployment in swept-source-based OCT real-time imaging systems.