Mid-infrared photon counting and resolving via efficient frequency upconversion

Abstract

Optical detectors with single-photon sensitivity and large dynamic range would facilitate a variety of applications. Specifically, the capability of extending operation wavelengths into the mid-infrared region is highly attractive. Here we implement a mid-infrared frequency upconversion detector for counting and resolving photons at 3 μm. Thanks to the spectrotemporal engineering of the involved optical fields, the mid-infrared photons could be spectrally translated into the visible band with a conversion efficiency of 80%. In combination with a silicon avalanche photodiode, we obtained unprecedented performance with a high overall detection efficiency of 37% and a low noise equivalent power of 1.8 × 10 − 17 W / Hz 1 / 2 . Furthermore, photon-number-resolving detection at mid-infrared wavelengths was demonstrated, for the first time to our knowledge, with a multipixel photon counter. The implemented upconversion detector exhibited a maximal resolving photon number up to 9 with a noise probability per pulse of 0.14% at the peak detection efficiency. The achieved photon counting and resolving performance might open up new possibilities in trace molecule spectroscopy, sensitive biochemical sensing, and free-space communications, among others.

Wide-field mid-infrared single-photon upconversion imaging

“…For the implemented image upconverter, the MIR laser illumination allows the use of narrow-band spectral filters to suppress the pump-induced noise. Besides, the coincident pulsed excitation provides an ultrashort time gate for the signal detection, thus significantly reducing the background noise from the ambient random scattering 51 . In order not to be limited by the dark noise of the camera itself, here we use a high-performance EMCCD to record the upconverted image.…”

“…The achieved temporal resolution of the optical gating is much narrower than the available electronic gate, for instance the nanosecond gate in an intensified CCD. Moreover, the self synchronization between the signal and pump pulses results in a negligible relative timing jitter 51 , which is essential in high-precision time-resolved analysis on the photoluminescence or other transient signals. Therefore, the implemented tomographic imaging provides an alternation to the MIR optical coherence tomography for addressing an important need in the characterization of structured materials.…”

Mid‐Infrared Single‐Photon Edge Enhanced Imaging Based on Nonlinear Vortex Filtering

“…An alternative promising solution lies in the nonlinear frequency upconversion, where the MIR signal is spectrally converted to the visible regime and subsequently detected by high‐performance silicon sensors. [ 19,20 ] A similar spirit was also manifested in MIR imaging based on non‐degenerate two‐photon absorption in wide‐bandgap semiconductors [ 21,22 ] or nonlinear interferometry with correlated dual‐color photons. [ 23–25 ] Indeed, current advances in charged coupled devices (CCDs) have led to the development of electron multiplying CCDs (EMCCDs) with single‐photon detection sensitivity and nearly‐unitary quantum efficiency.…”

“…Figure presents the artistic illustration of the experimental setup for the MIR edge enhancement imaging based on nonlinear frequency conversion. The involved light sources were originated from a passively synchronized fiber laser system, [ 20 ] which consisted of an Yb‐doped fiber laser (YDFL) at 1030 nm and an Er‐doped fiber laser at 1550 nm. Two dual‐color pulses were then used to prepare the MIR signal source at 3070 nm based on difference frequency generation.…”

“…The spectro‐temporal properties of relevant pulses were engineered to improve the nonlinear conversion efficiency. [ 20 ] Specifically, a spectrally bright MIR source with a narrow band was tailored to approach the phase‐matching bandwidth, and the pulse duration of the pump is optimized to be longer than that for the signal, thus ensuring the high intensity for the wrapped MIR photons. More information about the experimental setup and related results for the pulse characterization are given in Supporting Information.…”