Methods and apparatus for swept-source optical coherence tomography
AssigneeLightLab Imaging, Inc.
InventorJoseph M. Schmitt
Life of this patent
Estimating the term…
Abstract
In one embodiment of the invention, a semiconductor optical amplifier (SOA) in a laser ring is chosen to provide low polarization-dependent gain (PDG) and a booster semiconductor optical amplifier, outside of the ring, is chosen to provide high polarization-dependent gain. The use of a semiconductor optical amplifier with low polarization-dependent gain nearly eliminates variations in the polarization state of the light at the output of the laser, but does not eliminate the intra-sweep variations in the polarization state at the output of the laser, which can degrade the performance of the SS-OCT system.
Claims20
An optical coherence tomography data collection apparatus, the apparatus comprising
- a first gain element;
- a second gain element, each gain element having a different gain dependence on polarization;
- and
- a Fourier-domain mode-locked laser defining a cavity, the laser comprising
- a frequency tuning element in optical communication with the first gain element, the first gain element disposed within the laser cavity;
- the second gain element disposed outside the cavity,
- wherein the gain dependence on polarization of the first gain element is less than the gain dependence on polarization of the second gain element.
A method of OCT imaging comprising
- generating light from a Fourier-domain mode-locked laser, the laser defining a cavity, the laser comprising a first gain element, the first gain element disposed within the laser cavity;
- transmitting the generated light through a second gain element, the second gain element disposed outside the cavity, each gain element having a different gain dependence on polarization, wherein the gain dependence on polarization of the first gain element is less than the gain dependence on polarization of the second gain element;
- sampling interference signals at an output of a main interferometer using an analog-to-digital converter, the analog-to-digital converter clocked using a sample clock generator;
- and
- optimizing a drive frequency of a frequency tuning element of the laser with a digital control system, at least one control signal derived from the sample clock generator.
An optical coherence tomography data collection apparatus, the apparatus comprising
- an interferometer having an input and an output;
- an analog-to-digital converter configured to sample interference signals from the output;
- a first gain element;
- a second gain element, each gain element having a different gain dependence on polarization;
- a Fourier-domain mode-locked laser having a laser cavity, the laser in optical communication with the interferometer,
- the laser comprising
- a frequency tuning element in optical communication with the first gain element, the first gain element disposed within the laser cavity;
- the second gain element disposed outside the cavity;
- a sample clock generator configured to clock an analog-to-digital converter;
- and
- a digital control system configured to stabilize a drive frequency of the frequency tuning element of the laser, using a control signal derived from the sample clock generator,
- wherein the gain dependence on polarization of the first gain element is less than the gain dependence on polarization of the second gain element.
Dependencies are inferred from the claim text.