Fig. 1. (a) Schematic diagram of the experimental setup. L, lens; DM, dichromatic mirror; BP, bandpass filter; and PPLN, periodically poled lithium niobate crystal. (b) Theoretical calculation of phase mismatch within the crystal (co-linear case) in which MgO-PPLN crystal length is 30 mm, polarization period is $23.7\mu \mathrm{m}$, and temperature is controlled at 39°C. The pump light wavelength is 1080 nm. (c) Normalized upper conversion efficiency. The conversion bandwidth is 220 nm near $4.14\mu \mathrm{m}$.

Fig. 2. (a) Results of the images taken in the NETD test. (b) NETD matrix given by calculation based on Eq. (11). (c) NETD matrix obtained based on the conventional measurement method.

Fig. 3. (a) Comparison of measured and calculated NETDs as a function of QCE with different exposure time. (b) Central wavelengths of blackbody radiation at different temperatures (solid line) and corresponding NETD predictions (dashed line).

Fig. 4. (a) PCB used for the experimental tests. (b) Photographic results of the UCD (part of the area). The PCB is preheated.