Monitoring and active stabilization of laser injection locking using beam ellipticity.

We unveil a powerful method for the stabilization of laser injection locking based on sensing variations in the output beam ellipticity of an optically seeded laser. The effect arises due to an interference between the seeding beam and the injected laser output. We demonstrate the method for a commercial semiconductor laser without the need for any internal changes to the readily operational injection locked laser system that was used.

Analog stabilization of an electro-optic I/Q modulator with an auxiliary modulation tone.

Proper operation of electro-optic I/Q modulators relies on precise adjustment and control of the relative phase biases between the modulator's internal interferometer arms. We present an all-analog phase bias locking scheme where error signals are obtained from the beat between the optical carrier and optical tones generated by an auxiliary 2 MHz tone to lock the phases of all three involved interferometers for operation up to 10 GHz. With the developed method, we demonstrate an I/Q modulator in carrier-suppressed single-sideband mode, where the suppressed carrier and sideband are locked at optical power levels <-27 relative to the transmitted sideband.