Large dynamic range and wideband mid-infrared upconversion detection with BaGa4Se7 crystal

Direct detection of mid-infrared (MIR) at room temperature commonly suffers from the high background noise and the lack of ideal sensor material. An indirect upconversion method based on nonlinear optics bridges the desired MIR region to the well-developed near-infrared devices. In this paper, we report an experimental study of 3–8 µm MIR upconversion detection with a 1 µm laser-pumped B a G a 4 S e 7 crystal. This detection scheme is integrated with an optical parametric oscillator and an optical receiver to form a coherent source and detection system that offers high temporal (nanosecond time scale) and spectral resolution ( ≤ 3 c m − 1 ). The wide response band ( > 1.4 octave) and large dynamic range (11.5 orders) of this detection scheme benefits from the superior optical properties of this non-oxide crystal, and a minimum detectable energy of 1.02 fJ/pulse is observed with an InGaAs p-i-n photodiode. The upconversion technique outperforms commercial HgCdTe detectors in terms of both sensitivity (2–4.5 orders better) and wavelength response flatness. The aforementioned characteristics of this integrated MIR source and detection system make it of significant interest for applications in high-resolution gas analysis and spectral imaging.