Dynamic properties of wavelength switching in a widely tunable semiconductor laser for optical coherence tomography

We present results on the investigation of the dynamics of wavelength switching in a monolithically integrated widely tunable semiconductor ring laser for application in swept source optical coherence tomography. In this application wavelength switching within several tens of nanoseconds is desirable to reduce motion blur artefacts during imaging. The device under test is realized in an InGaAsP/InP platform, operates around 1530 nm wavelength and has been shown to have a tuning range over 50 nm. Both measurements and simulations of the wavelength switching behavior of the laser are presented. Tuning is achieved using voltage controlled electro-refractive phase modulators with a response faster than 1 GHz and negligible residual thermal tuning. The fastest switching strategy, of the three that we compare in our simulations, is shown to be the one that relies on rapid power-off of the origin wavelength. The longitudinal cavity mode position, that has an important impact on the switching time and switching stability, is shown to be hard to predict after switching due to gain-phase coupling in the amplifier.