Mid-infrared single-photon 3D imaging

Abstract

Active mid-infrared (MIR) imagers capable of retrieving three-dimensional (3D) structure and reflectivity information are highly attractive in a wide range of biomedical and industrial applications. However, infrared 3D imaging at low-light levels is still challenging due to the deficiency of sensitive and fast MIR sensors. Here we propose and implement a MIR time-of-flight imaging system that operates at single-photon sensitivity and femtosecond timing resolution. Specifically, back-scattered infrared photons from a scene are optically gated by delay-controlled ultrashort pump pulses through nonlinear frequency upconversion. The upconverted images with time stamps are then recorded by a silicon camera to facilitate the 3D reconstruction with high lateral and depth resolutions. Moreover, an effective numerical denoiser based on spatiotemporal correlation allows us to reveal the object profile and reflectivity under photon-starving conditions with a detected flux below 0.05 photons/pixel/second. The presented MIR 3D imager features high detection sensitivity, precise timing resolution, and wide-field operation, which may open new possibilities in life and material sciences.

Wide-field mid-infrared hyperspectral imaging beyond video rate

“…The resulting wide-field operation is critical to implement a fast snapshot acquisition, which contrasts with previous scanning-assisted modalities based on temperature tuning 25 , 35 , crystal rotation 33 , 34 , or object translation 36 . The wide-field supremacy has been manifested in high-speed MIR imaging within a narrow spectral band 31 , 42 , but the potential of simultaneous broadband capability has not yet been revealed in the realm of spectral imaging. In parallel, high-fidelity spectral mapping is required to preserve the infrared absorption profile at each spatial coordinate.…”

“…A CPLN nonlinear crystal is placed at the Fourier plane to perform the SFG process under a spatially and temporally overlapped pump pulse. The CPLN is fabricated with a linearly-ramping polling period from 16 to 24 μm, which permits a wide-field and broad-spectrum upconversion imaging due to the self-adapted quasi-phase-matching for various incident angles and signal wavelengths 28 , 31 , 42 . Hence, the spatial and spectral information is simultaneously transferred to the polychromatic upconverted field in the visible region, as illustrated in Fig.…”

“…We note that the presented spectral imaging modality is ready to include the depth information by tuning the pump pulse delay for the optical gating 42 , 49 , which enables rapid data acquisition in all four dimensions, i.e., a ( x , y , z , λ) hypercube. The envisioned MIR spectro-tomography would pave the way for high-speed and high-throughput characterization of biological and material specimens.…”

Time-of-flight resolved stimulated Raman scattering microscopy using counter-propagating ultraslow Bessel light bullets generation

“…Recently, a Bessel beam pulse with arbitrary group velocity in free space has been proposed theoretically through either a deformed pulse front 17 or nanophotonic layer 18 , and generated experimentally using a combination of a spatial light modulator (SLM) and several phase plates 19 . (ii) If we measure the interaction between the two light pulses with different via a nonlinear optical process, the depth information whereby the nonlinear interaction 20 , 21 takes place can be controlled by their relative speed or relative time-of-flight. In this case, the temporal resolution becomes the laser pulsewidth, e.g., hundreds of femtoseconds (fs) in typical SRS imaging.…”