Faraday effect-based semiconductor laser-frequency stabilization at the Rb absorption line

In order to stabilize the oscillation frequency of a semiconductor laser, we use the external reference-point, in this instance, to determine the degree to which the observed frequency deviates from the reference signal. This is done, by modulating the laser's injection current. In so doing, however, the oscillation spectrum inevitably broadens. We therefore devised a method that takes full advantage of the Faraday effect to stabilize the oscillation frequency, yet needs no direct modulation.