Near-infrared imaging InGaAs sensors show lower performances in term of noise and sensitivity compared to silicon based cameras. Image frequency conversion from near-infrared to visible wavelengths by nonlinear parametric sumfrequency mixing in a χ⁽²⁾ medium should increase detection performances in active imaging applied to long range target identification. For such applications, both energy conservation and phase matching conditions are ideally suited to efficient upconversion. Nevertheless, the available resolution still hampers the development of upconversion imagers.

In this paper, we upconvert images provided by 1.5 μm collimated continuous wave lasers illuminating resolution targets and small objects. Using a 2.7 nm wide pump spectrum at 1064 nm, we resolve 56x64 spatial elements whereas we obtained only 16x19 spatial elements with a narrow spectrum pump laser at 1064 nm with the same beam diameter and 8x8 spatial elements with a 0.5 mm thick crystal. These results are compatible with long range target recognition. A laboratory scale experiment of active imaging of diffusive objects is shown as an illustration.

Date Published: 24 May 2018
PDF: 7 pages
Proc. SPIE 10677, Unconventional Optical Imaging, 1067703 (24 May 2018); doi: 10.1117/12.2306279

Published in SPIE Proceedings Vol. 10677:
Unconventional Optical Imaging
Corinne Fournier; Marc P. Georges; Gabriel Popescu, Editor(s)