High brightness terahertz quantum cascade laser with near-diffraction-limited Gaussian beam
Rusong Li, Yunfei Xu, Shichen Zhang, Yu Ma, Junhong Liu, Binru Zhou, Lijun Wang, Ning Zhuo, Junqi Liu, Jinchuan Zhang, Shenqiang Zhai, Shuman Liu, Fengqi Liu, Quanyong Lu
Abstract
Abstract High-power terahertz (THz) quantum cascade laser, as an emerging THz solid-state radiation source, is attracting attention for numerous applications including medicine, sensing, and communication. However, due to the sub-wavelength confinement of the waveguide structure, direct beam brightness upscaling with device area remains elusive due to several mode competition and external optical lens is normally used to enhance the THz beam brightness. Here, we propose a metallic THz photonic crystal resonator with a phase-engineered design for single mode surface emission over a broad area. The quantum cascade surface-emitting laser is capable of delivering an output peak power over 185 mW with a narrow beam divergence of 4.4° × 4.4° at 3.88 THz. A high beam brightness of 1.6 × 10 7 W sr −1 m −2 with near-diffraction-limited M 2 factors of 1.4 in both vertical and lateral directions is achieved from a large device area of 1.6 × 1.6 mm 2 without using any optical lenses. The adjustable phase shift between the lattices enables a stable and high-intensity surface emission over a broad device area, which makes it an ideal light extractor for large-scale THz emitters. Our research paves the way to high brightness solid-state THz lasers and facilitates new applications in standoff THz imaging, detection, and diagnosis.