Precise frequency stabilization technique for 850nm vertical cavity surface emitting lasers by controlling their optical beat frequency

Abstract

We have demonstrated a compact and inexpensive frequency stabilization technique for commercially available 1mW, 850nm Vertical Cavity Surface Emitting Laser (VCSEL) using a Fabry-Perrot Resonator (FPR) as frequency standard. We have performed frequency discrimination using a transmitted light from FPR, and frequency stabilization has been carried out by electrical negative feedback to injection current. Optical frequency fluctuation of VCSEL is estimated by error signal, and its stability is evaluated by Allan variance. We have achieved to detect optical beat frequency signal of 850nm type VCSEL for the first time, by fabricating two sets of frequency stabilized VCSEL, which are quite similar with each other by controlling each locking frequency. We have estimated VCSEL's frequency accurately fluctuations from the beat signal. As a result, we have successfully suppressed the amount of frequency fluctuations for the free-running VCSEL of as much as 600MHz to be within 80MHz. In this paper, we propose compact, inexpensive and precise frequency stabilization for 850nm VCSEL, and describe an accurate method for estimating its fluctuations.