Frequency Stabilization of an InP-Based Integrated Diode Laser Deploying Electro-Optic Tuning

We present the frequency stabilization of a monolithically integrated extended cavity single mode InP diode laser using the Pound-Drever-Hall (PDH) frequency locking technique. The laser is a multi-section distributed Bragg reflector (DBR) laser with an intra-cavity ring resonator, fabricated using an InP active-passive integration technology. The laser is locked to a 700 kHz wide resonance of a Fabry-Perot etalon. The single electrical feedback is applied on the reverse biased rear DBR section of the laser, used to tune the lasing mode. This is the first time to our knowledge that the feedback is applied on a reverse biased, voltage controlled section of an integrated laser cavity. In our implementation the tuning is based on electro-optic effects avoiding significant thermal effects in the tuning element. We demonstrate a linewidth reduction down to 5 kHz and frequency noise suppression of about 30 dB at 10 Hz offset frequency. The bandwidth of the control loop is about 500 kHz, limited by the phase delay of components in our loop.