Room-temperature mid-infrared single-photon spectral imaging

The spectral imaging and detection of mid-infrared wavelengths is emerging as an enabling technology of great technical and scientific interest, primarily because important chemical compounds display unique and strong mid-infrared spectral fingerprints that reveal valuable chemical information. Modern quantum cascade lasers have evolved as ideal coherent mid-infrared excitation sources, but simple, low-noise, room-temperature detectors and imaging systems lag behind. We address this need by presenting a novel, field-deployable, upconversion system for sensitive, two-dimensional, mid-infrared spectral imaging. A room-temperature dark noise of 0.2 photons/spatial element/second is measured, which is a billion times below the dark noise level of cryogenically cooled InSb cameras. Single-photon imaging and a resolution of up to 200 x 100 spatial elements are obtained with a record-high continuous-wave quantum efficiency of similar to 20% for polarized incoherent light at 3 mu m. The proposed method is relevant for existing and new mid-infrared applications such as gas analysis and medical diagnostics.