Ultra-low threshold continuous-wave quantum dot mini-BIC lasers

Highly compact lasers with ultra-low threshold and single-mode continuous wave(CW)operation have been a long sought-after component for photonic integrated circuits(PICs).Photonic bound states in the continuum(BICs),due to their excellent ability of trapping light and enhancing light-matter interaction,have been investigated in lasing configurations combining various BIC cavities and optical gain materials.However,the realization of BIC laser with a highly compact size and an ultra-low CW threshold has remained elusive.We demonstrate room temperature CW BIC lasers in the 1310 nm O-band wavelength range,by fabricating a miniaturized BIC cavity in an InAs/GaAs epitaxial quantum dot(QD)gain membrane.By enabling effective trapping of both light and carriers in all three dimensions,ultra-low threshold of 12μW(0.052 kW cm^(-2))is achieved at room temperature.Single-mode lasing is also realized in cavities as small as only 5×5 unit cells(~2.5×2.5μm^(2) cavity size)with a mode volume of 1.16(λ/n)^(3).The maximum operation temperature reaches 70℃ with a characteristic temperature of T_(0)~93.9 K.With its advantages in terms of a small footprint,ultra-low power consumption,and adaptability for integration,the mini-BIC lasers offer a perspective light source for future PICs aimed at high-capacity optical communications,sensing and quantum information.