Ultrasharp, Cavity Enhanced, Broadly Tunable Infrared Detection Using Colloidal Quantum Dots

After the success of semiconductor nanocrystals as light sources for displays in the visible range, the infrared range now offers a complementary playground. Applications requiring chemical contrast in images and applications to LIDAR technology incentivize the development of devices with narrow spectral responses. However, the solutions that rely on introducing notch filters still suffer from imperfect transmission at the wavelength of interest in a spectral range where their detection is already difficult. Here, we explore the integration of a short-wave infrared detector directly into a dielectric microcavity. Our approach simultaneously achieves ultranarrow absorption lines below 30 cm^-1 at a telecom wavelength, together with a broadband, continuous, postfabrication spectral tunability over 1200 cm^-1. By taking advantage of the field magnification inside the cavity, we demonstrate that the spectral shaping properties can be obtained while maintaining performances on par with an uncoupled device, stressing the benefit of this method compared to filter-only approaches.