Multicolor Time-Resolved Upconversion Imaging by Adiabatic Sum Frequency Conversion

Upconversion imaging, where mid-infrared (IR) photons are converted to visible and near-IR photons via a nonlinear crystal and detected on cheap and high-performance silicon detectors, is an appealing method to address the limitations of thermal sensors that are expensive, often require cooling, and suffer from both limited spectral response and limited spatial resolution as well as poor sensitivity. However, phase matching severely limits the spectral bandwidth of this technique, therefore requiring serial acquisitions in order to cover a large spectrum. Here, a novel upconversion imaging scheme covering the mid-IR based on adiabatic frequency conversion is introduced. The study presents mid-IR multicolor imaging and demonstrates simultaneous imaging on a complementary metal–oxide–semiconductor (CMOS) camera of radiation spanning a spectrum from 2 to 4 µm. This approach being coherent and ultrafast in essence, spectrally resolved spatiotemporal imaging is further demonstrated that allows spatially distinguishing the temporal evolution of spectral components.