Integrated Single Frequency, High Power Laser Sources Based on Monolithic and Hybrid Coherent Beam Combining

Abstract

Monolithic and hybrid integration platforms are both important for photonic integrated circuits. It is desirable for the laser sources integrated in both platforms to provide high power and single frequency operation for many emerging applications. However, it is difficult to realize simultaneous high power and single frequency operation by using conventional semiconductor distributed feedback lasers. Integrated coherent beam combining (CBC) is a promising solution to overcome this challenge. In this paper, coherently combined, integrated diode laser systems are experimentally demonstrated through both monolithic and hybrid CBC. For monolithic CBC of broad-area lasers in the InP platform, two single triangular-lattice photonic crystal (PC) Bragg lasers are combined. The measurement results show that the output power of the combined PC Bragg lasers is increased and the single frequency operation is maintained. As for the hybrid CBC, a chipscale coherently combined laser system is experimentally demonstrated in the InP-Si3 N4 platform through the manipulation of optical feedback at different output ports of the coupled laser cavities. Coherent combining of two InP-based reflective semiconductor amplifiers are obtained by use of the cross-coupling provided by an adiabatic 3-dB coupler in silicon nitride, with a combining efficiency of ∼92%.