All-passive upconversion of incoherent near-infrared light at intensities down to 10${}^{-7}$ W/cm${}^2$

Rabeeya Hamid, Demeng Feng, Pournima Narayanan +10

Frequency upconversion, which converts low-energy photons into higher-energy ones, typically requires intense coherent illumination to drive nonlinear processes or the use of exter…