Twenty-milliwatt, high-power, high-efficiency, single-mode, multi-junction vertical-cavity surface-emitting lasers using surface microstructures
Yao Xiao, Pei Miao, Jun Wang, Heng Liu, Yudan Gou, Zhicheng Zhang, Bangguo Wang, Wuling Liu, Qijie Wang, Guoliang Deng, Shouhuan Zhou
Abstract
High-power, high-efficiency single-mode vertical-cavity surface-emitting lasers (VCSELs) are crucial in the realm of green photonics for high-speed optical communication. However, in recent years, the power and efficiency of single-mode VCSELs have remained relatively low and have been progressing slowly. This study combines theoretical models with experiments to show that multi-junction cascaded 940 nm VCSELs based on surface microstructures can achieve high power, high efficiency, and low divergence in single-mode laser output. Simulations show multi-junction VCSELs with surface microstructures can boost mode modulation capabilities, power, and efficiency, potentially allowing high-power single-mode VCSELs to surpass 60% efficiency. Using this technique, the 6 μm oxide aperture VCSELs with surface relief of different diameters were fabricated. The single-mode VCSELs with the output power of 20.2 mW, side-mode suppression ratios greater than 35 dB, 42% electro-optical efficiency, and a 9.8° divergence angle (at 1/e 2 ) under continuous-wave operation were demonstrated. Near-field images verified its fundamental mode operation. To the best of the authors’ knowledge, this is the highest single-mode power recorded for a single-unit VCSEL to date, almost twice the currently known record, while still maintaining a very high electro-optical conversion efficiency. This research will provide valuable references for the further development and application of high-power, high-efficiency single-mode semiconductor lasers.