Linewidth control for optical heterodyne beat of 850-nm vertical cavity surface emitting lasers

Abstract

We have achieved a simple and precise frequency stabilization technique for commercially available 1mW, 850nm vertical cavity surface emitting laser (VCSEL) based on optical heterodyne beat frequency control by introducing two sets of frequency stabilized VCSEL's with Fabry-Perot resonator (FPR) as frequency discriminator. The stabilized VCSEL's were quite similarly fabricated with each other, in which the electrical negative feedback was supplied for stabilization. We have also detected optical heterodyne beat between these two VCSEL's by adjusting the locking frequency of each VCSEL. Thus, we have further reduced the frequency fluctuations from these stabilized VCSEL's by controlling their feedback current so that the variation in the optical beat frequency should be minimized. As a result, we have successfully suppressed the amount of optical beat frequency fluctuations within 2MHz at measuring time of 1 sec. That is, the attained Allan variance is within the order of 10 -9 . In this work, we have achieved simple and inexpensive and precise frequency stabilization for 850nm VCSEL by optical heterodyne beat frequency control, which is quite applicable to nanomanufacturing.