Feature Of The Week 12/8/2013: Tuning of Vernier Tuned DBR Lasers for Optical Comb Swept Source OCT
Monolithic Vernier tuned distributed Bragg reflector (VT-DBR) lasers are expected to become one of the most promising sources for optical comb swept source optical coherence tomography (SS-OCT) with reduced sensitivity roll-off due to a long coherence length, potential capability for a very fast A-scan rate, and low cost with monolithic structure. However, mainly four problems inhibited an ideal implementations: 1) frequencies deviate from the targeted values when scanned, 2) large amounts of noise appear associated with abrupt changes in injection currents, 3) optically aliased noise appears due to a long coherence length, and 4) the narrow wavelength coverage of a single chip limits resolution. These problems have been solved by developments of a method of dynamical frequency-tuning, a method of selective data sampling to eliminate current switching noise, an interferometer to reduce aliased noise, and an excess-noise-free connection of two serially scanned lasers to enhance resolution. An optical frequency comb SS-OCT system was achieved using super-structure grating distributed Bragg reflector lasers with good sensitivity, no sensitivity roll-off within the principal depth range, good dynamic range of 55-72 dB (depended on the depth) within the principal depth range, and OCT imaging of excellent image penetration. Further improvements of SS-OCT with VT-DBR laser are suggested by numerical simulation of PSF over extended depth ranges.
For more information see recent Article. Courtesy of Kohji Ohbayashi from Advanced Imaging Co. Ltd.