AlGaAs-on-insulator microresonators satisfying broadband phase matching for longwave infrared spectral upconversion

Recent advancements in nonlinear optics have significantly revolutionized the field of integrated photonics, offering on-chip solutions for a diverse array of cutting-edge applications. The strategic implementation of second-order nonlinear interactions within compact devices not only enhances energy conversion efficiency but also unlocks novel operational paradigms, highlighting their potential for room-temperature longwave infrared detection at the single-photon level. In this study, we present spectral frequency upconversion from the longwave infrared (LWIR) to the near-infrared (NIR) regime, utilizing specifically designed AlGaAs-on-insulator (AlGaAsOI) microresonators. By developing a comprehensive theoretical framework for the χ ⁽²⁾ nonlinear process and employing advanced numerical methods to optimize conversion efficiency in hybrid whispering-gallery-mode microresonators, we have engineered devices capable of achieving phase matching across a bandwidth exceeding 160 THz between the signal and pump fields. Our numerical simulations demonstrate that a single device can upconvert spectra over a range of more than 1 µm by simply tuning the pump wavelength. Remarkably, in addition to their exceptional bandwidth performance, our results show that a continuous-wave pump power as low as 5 mW can yield an internal quantum efficiency of 10% in representative designs, achieving a remarkable improvement over previous studies. Furthermore, we have numerically demonstrated that high-fidelity, wide-band spectral upconversion can be realized through the implementation of microresonator arrays on a single chip, coupled with simultaneous adjustment of both pump wavelength and power. This research underscores the tremendous potential of AlGaAsOI microresonators for nonlinear optical applications, particularly in the realm of longwave infrared photonics. The demonstrated capabilities of these devices open new avenues for advanced photonic systems and their applications in spectroscopy, sensing, and quantum technologies.