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In monolithic photonic integrated circuits (PICs), an optimized active/passive integration is needed to provide efficient coupling and low amount of interface reflections between amplifiers and passive components. A 1300 nm semiconductor optical amplifier (SOA) on InP substrate and optimized for butt-joint reflections is investigated. Material performance were assessed from measurements of broad area lasers. Room temperature operation reveals 1.2 W single facet output power with threshold current around 100 A/cm2 per well. Characteristic temperatures of T0 = 75 K and T1 = 294 K were obtained. A compact model description of the SOA, suitable for the design of PICs and rate equation analysis, was applied to parametrize the unsaturated gain measurements. Current injection efficiency of 0.65, transparency carrier density of 0.57 1018 cm−3, and free carrier absorption losses up to 15 cm−1 were extracted from fitting the data. The model is verified with measurements of optical gain saturation. A modal gain of 15 dB for a 600 μm long narrow ridge SOA leads to output saturation power higher than 30 mW at 7 kA/cm2. This building block contributes to the development of an InP monolithic integration technology in the 1300 nm range, which can enable the use of photonic integrated circuits in many kind of applications.

Residual amplitude modulation of the phase modulator deployed in Pound-Drever-Hall frequency stabilization is an effect known to cause instabilities to the absolute wavelength of the stabilized laser. We present measurements and analysis of the residual amplitude modulation in an InP-based waveguide electro-optic phase modulator. The modulator is monolithically integrated in the output waveguide of a tuneable laser. The effects on the frequency stabilization of such a laser system to a reference etalon using a Pound-Drever-Hall frequency stabilization scheme are quantified. Frequency offset values in the stabilization point from the reference Fabry-Perot etalon resonance caused by the amplitude modulation are predicted and optimum operating points to minimize residual amplitude modulation are discussed. By operating an electro-refractive phase modulator at the proper bias point, we show that frequency offsets corresponding to less than 3 × 10-3 of the reference cavity full-width half-maximum can be achieved.

An InP-based, monolithically integrated multiwavelength laser with optical feedback is presented. We demonstrate the performance of the dual-wavelength operation. Single-mode lasing is obtained for each of the two channels within a temperature range from 16 to 30 °C and an injection current range from 30 to 70 mA without mode-hopping. This is due to the combined filtering functions of an arrayed waveguide grating and a distributed Bragg reflector. A method that makes use of weak optical feedback is demonstrated to improve the stability of each single-mode. With this method, sustained relaxation oscillations that are excited by on-chip parasitic reflections are damped and linewidths in both channels are narrowed to around 400 kHz compared to the linewidth of 1 MHz that is obtained when no feedback is applied. The suppression ratio of the relaxation-oscillation-induced side peaks is measured to be over 45 dB for two simultaneously operated channels.