High-power and low-threshold 1200 nm InGaAs/GaAs quantum-wells VECSEL grown by MOCVD

Abstract

Here, we demonstrate an InGaAs/GaAs quantum-wells (QWs) based vertical-external cavity surface emitting laser (VECSEL) with multi-watt emitting beyond 1200 nm. The development is motivated by the need for high-performance 1200 nm laser sources, which are located in the C–H bond photoacoustic tomography window and atmospheric transmission band. In the exploration, strain compensation, epitaxy growth, and package strategy are all optimized for effective performance improvement. Highly strained InGaAs/GaAs QWs epitaxy structures are grown on GaAs substrate with high crystalline quality by metal-organic chemical vapor deposition (MOCVD) technology. With effective thermal management, the thermal impedance of the chip is as low as about 0.92 K/W. As a result, the 1200 nm VECSEL can emit a power of 9.4 W under continuous wave (CW) operation, and the threshold pump power density is as low as about 1.61 kW/cm2. The VECSEL can also operate at a quasi-continuous wave (QCW) emission with tunable pulse width and repetition rates. Under a duty cycle of ∼9.5%, the VCSEL is with a peak power of 16.6 W and a slope efficiency of about 15.5%, and the corresponding pulse energy is as high as about 1.57 mJ. No thermal rollover is observed. This exploration significantly broadens the VECSEL performance and can be regarded as an extension and enrichment of the earlier works on this topic.