[ThA1] III-V Nanostructures: From Spintronics to Advanced Lasers

9:45 AM - 10:00 AM JST(12:45 AM - 1:00 AM UTC)

[ThA1-05] Short-cavity InAs/GaAs Quantum-Dot Lasers with 25-nm GaAs Spacers

〇Hexing Wang¹, Huiwen Deng¹, Jae-Seong Park¹, Xuanchang Zhang¹, Cong Lu², Haifen Kan¹, Haotian Zeng¹, Yangqian Wang¹, Dominic Gallagher³, Junhao Liu¹, Danqi Lei¹, Hui Jia¹, Wei Li², Peter M. Smowton⁴, Siming Chen¹, Alwyn Seeds¹, Huiyun Liu¹, Mingchu Tang¹ (1. Dept. Electron. & Electr. Eng., Univ. College London (UK), 2. College Mater. Sci. & Eng., Beijing Univ. Tech. (China), 3. Photon Design (UK), 4. School Phys. & Astron., Cardiff Univ. (UK))

Thick GaAs spacers (>37.5 nm) are widely used in stacked InAs/GaAs quantum dot (QD) lasers to avoid strain accumulation. However, these thick spacers reduce volumetric dot density and increase carrier transport time, therefore limiting the modal gain and modulation bandwidth. Here, we reduced the GaAs spacer thickness to 25 nm while maintaining optical and structural qualities, confirmed by photoluminescence (PL) and bright-field scanning transmission electron microscopy (BF-STEM). Ridge waveguide lasers incorporating the 11-layer QDs show a low threshold current density of 178 A/cm² at room temperature (pulsed) and sustains lasing up to 180 °C. Furthermore, the ground-state lasing is observed in a short 200-μm cavity device without high reflectivity coatings, and the threshold modal gain was estimated to be above 60 cm^-1. These results show that thin spacer design gives a viable route towards the high temperature and high gain QD lasers for next-generation optical interconnects.