Core-shell microdisk with InGaN/GaN quantum wells for dual-band whispering gallery mode lasing

The development of high-quality, stable, and cost-effective micro/nano dual-band lasing remains a crucial challenge for multifunctional applications. In this study, we demonstrate high-Q dual-band WGM lasing in an independent core-shell microdisk, emitting both ultraviolet and blue lasing. The GaN-based microdisk with InGaN/GaN quantum wells serves as the core, while a SiO 2 layer is deposited on the sidewalls to construct the core-shell microdisk. This independent structure is fabricated using the graphically epitaxial lift-off method, which effectively mitigates light leakage issues associated with the substrate and facilitates flexible device integration. Compared to the microdisk without a SiO 2 shell coating, the threshold of ultraviolet lasing in the core-shell microdisk is reduced by 1.6 times, the Q-factor is enhanced by 21.7%, and blue lasing is successfully achieved. The underlying physical mechanisms are thoroughly analyzed through steady-state and time-resolved photoluminescence, along with finite-difference time-domain simulations. Furthermore, cooling from 300 K to 100 K significantly enhances lasing performance, increasing the Q-factor by factors of 1.7 and 1.9 in the ultraviolet and blue bands, respectively. Additionally, due to thermal expansion and thermo-optical effects, the blue lasing mode exhibits a temperature-dependent wavelength shift with a slope of -0.007 nm/K. The generation and optimization of dual-band lasing within a single microcavity offer new opportunities for broadband optical communication, high-sensitivity multi-wavelength biosensing, multi-label biomedical imaging, and high-density optical storage.