Fast ultraviolet-C photonics: generating and sensing laser pulses on femtosecond timescales

Photonic devices operating in the ultraviolet UV-C range (100-280 nm) have diverse applications from super-resolution microscopy to optical communications, and their advances promise to unlock new opportunities across science and technology. However, generating and detecting ultrafast light signals in this spectral range remains a major challenge. Here, we report an integrated UV-C source-sensor platform that combines phase-matched second-order processes in nonlinear optical crystals for the efficient generation of femtosecond UV-C laser pulses with a new class of room temperature photodetectors based on two-dimensional (2D) semiconductors. Unexpectedly, these 2D sensors exhibit a linear to super-linear photocurrent response to pulse energy, a highly desirable property, laying the foundation for UV-C-based photonics operating on femtosecond timescales over a wide range of pulse energies and repetition rates. As proof of concept, we demonstrate a free-space communication system.