Coherence-property evaluation of tunable VCSELs for SS-OCT by interferometric method with a 3×3 coupler

We have demonstrated a coherence-property evaluation of a tunable vertical-cavity surface-emitting laser for swept-source optical coherence tomography by using a 3×3 coupler interferometer, which tells us the time-resolved electric field of the source light. We improve the method considering time-variance of experimental elements including the 3×3 coupler to accurately evaluate the coherence properties. The coherence lengths derived by this improved 3×3-coupler method agree well with those derived by the previously reported method that relies on the depth variation of the noise floor.