Swept frequency laser for FD OCT with intracavity element and method of operation
View Patent ↗A frequency swept laser source that generates an optical signal that is tuned over a spectral scan band at single discrete wavelengths associated with longitudinal modes of the swept laser source. Laser hopping over discrete single cavity modes allows long laser coherence length even under dynamic very high speed tuning conditions. A ramp drive to the laser is used to linearize laser frequency tuning. A beam splitter is used to divide the optical signal between a reference arm leading to a reference reflector and a sample arm leading to a sample. A detector system detects the optical signal from the reference arm and the sample arm for generating depth profiles and images of the sample.
1. An optical coherence analysis method, comprising:
generating an optical signal that is tuned over a spectral scan band with a tunable mode-hopping swept laser source that includes a laser cavity defining longitudinal modes, a semiconductor gain chip in the laser cavity, and a tuning element for the laser cavity, the tuning element comprises a tunable pass band that restricts the swept laser source to lasing at no more than one of the longitudinal modes;
emitting, from the swept laser source, the optical signal one wavelength mode at a time and tuning discretely over wavelengths associated with the longitudinal modes of the laser cavity;
dividing the optical signal between a reference arm leading to a reference reflector and a sample arm leading to a sample;
detecting the optical signal from the reference arm and the sample arm; and
controlling a drive current to the semiconductor gain chip.
2. An optical coherence analysis method as claimed in claim 1 , wherein controlling the drive current comprises modulating the drive current to stabilize a power output of the swept laser source.