Upconversion detection of long-wave infrared radiation from a quantum cascade laser

Abstract

Broadly tunable upconversion is demonstrated for long-wave infrared (LWIR) detection. The upconversion system is evaluated by the detection of 50 ns pulses from a narrow linewidth tunable quantum cascade laser (QCL) in the 9.4 to 12 µm range. The LWIR signal is mixed with a 1064 nm laser beam in a silver gallium sulfide (AgGaS 2) crystal, resulting in an upconverted signal in the 956 to 977 nm range, using angle tuning for optimal phase-matching. This allows for efficient, high speed detection using a standard silicon detector. A theoretical model including absorption and diffraction shows qualitative agreement with experimental data.

Long-wave Infrared Upconverter

“…An upconverter is demonstrated in this study showing how the IR radiation can be frequency converted via the nonlinear process of sum-frequency generation (SFG), which allows for the use of silicon detectors to acquire the upconverted signal [9]. Silver gallium sulfide (AgGaS2) is the preferred nonlinear material in the 5 to 10 µm range because of its high nonlinear coefficient of deff ~13 pm/V, broad transparency range from 550 nm to 12 µm, and being commercially available.…”

Upconversion raster scanning microscope for long-wavelength infrared imaging of breast cancer microcalcifications

“…The AgGaS 2 crystal was mounted on a piezo controlled rotation stage (ECR3030, Attocube) for angle tuned birefringent phasematching, converting the LWIR signal to the 950 to 980 nm range. For further details see ref [25]. Three short-pass filters (FESH1000, Thorlabs) and a long-pass filter (FELH900, Thorlabs) were used in line before the upconverted signals were detected with a silicon detector (PDA 100A, Thorlabs).…”

“…Figure 4(a) shows the multispectral images obtained with upconverted at 1040, 1032, 1020, 1005, 970, 962, 950, 910, 881, 875, 860, and 850 cm −1 . The wavelength of interest was set for the QCL with an illumination bandwidth of ∼1 cm −1 and the nonlinear crystal was rotated for optimal conversion efficiency for each wavelength [25]. Reference measurements on an empty area of the BaF 2 sample mount were performed at each wavelength for calculation of the sample absorbance.…”

“…Frequency upconversion is an alternative approach to direct detection of infrared radiation [23][24][25]. Converting long-wavelength infrared emission into the visible/near infrared range via nonlinear frequency conversion allows for the use of silicon detectors.…”

Molecular optomechanical frequency upconversion at the single-photon level

“…As an outlook, we propose to leverage constructive interference between signals coming from an array of coherently * corresponding authors: tobias.kippenberg@epfl.ch † chris.galland@epfl.ch pumped up-converters in order to increase further the strength of the converted signal over the incoherent thermal noise. While coherent conversion from the MIR to the VIS-NIR domain has so far been achieved by sum-frequency generation in bulk non-linear crystals [15][16][17][18], these schemes operated under several Watts of pump power and required phase-matching between the different fields propagating in the crystal. Our scheme, on the contrary, relies solely on the spatial overlap of the two incoming fields.…”