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We report on the free-running and frequency stabilized operation of a ring resonator-tuned full-band tuneable laser. The laser is a monolithically integrated semiconductor ring laser tuneable over 34 nm, from 1522-1556 nm, fabricated using a commercially-available, InP-based, active-passive foundry technology. The mode selection is implemented using the Vernier effect by reverse-biasing voltage-controlled electro-optically tuned ring resonators. The laser exhibits a typical intrinsic linewidth of 110 kHz over the C-band and a side-mode suppression ratio (SMSR) exceeding 50 dB. The linewidth over the tuning range does not significantly vary, showing that the tuning mechanism does not cause linewidth broadening. The power dissipated in the tuning elements is 1.4 mW per ring. Using the same reverse bias voltage-controlled electro-optic tuning, we also demonstrate the locking of the laser to a high-finesse etalon using Poun-Drever-Hall frequency locking. Our implementation requires a single control loop because of the reverse bias tuning. All deployed tuning effects in the phase modulators have the same sign therefore resulting in a flatter frequency dependent phase response compared to current injection feedback. The control loop has a bandwidth of 500 kHz and a control range of 2.9 GHz. We report 1 kHz level linewidth for millisecond observation times for the stabilized laser.

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.

We investigate the effect of a ring resonator on the linewidth and output spectrum of monolithically integrated extended cavity multi-section DBR lasers with an intra-cavity ring resonator. The goal is to achieve an understanding of whether and how the use of an additional ring filter improves the performance of a DBR laser on the aspects of the SMSR and intrinsic linewidth using the capabilities of the InP active-passive integration platform. The laser output spectrum is in good agreement with our theoretical calculations from a steady-state spectral model. A side-mode suppression ratio between 60 and 70 dB is measured for a range of operating semiconductor optical amplifier currents. The frequency noise power spectral density is measured for a range of output power levels. A minimum intrinsic linewidth of 63 kHz is reported. We compare the measured Lorentzian linewidths with our theoretical expectations and present estimates of the possible linewidth improvement with the available photonic integration technology used in this work.