Electrically pumped semiconductor laser with low spatial coherence and directional emission

• Main Authors: Kim, Kyungduk, Bittner, Stefan, Zeng, Yongquan, Liew, Seng Fatt, Wang, Qijie, Cao, Hui
• Other Authors: School of Electrical and Electronic Engineering
• Format: Article
• Language: English
• Published: 2019
• Subjects: Optical Resonators; Semiconductor Lasers; Engineering::Electrical and electronic engineering
• Online Access: https://hdl.handle.net/10356/90317; http://hdl.handle.net/10220/49906
• Institution: Nanyang Technological University

We design and fabricate an on-chip laser source that produces a directional beam with low spatial coherence. The lasing modes are based on the axial orbit in a stable cavity and have good directionality. To reduce the spatial coherence of emission, the number of transverse lasing modes is maximized by fine-tuning the cavity geometry. In a cavity with the size of hundreds of micrometers, 1000 transverse modes lase simultaneously and independently, reducing the speckle contrast to 0.03. Decoherence is reached in a few nanoseconds as a result of frequency detuning of lasing modes. Such rapid decoherence will facilitate applications in ultrafast speckle-free full-field imaging.