Compact self-illuminated image upconversion system based on intracavity second-harmonic generation

Abstract

We present an image upconversion system based on intracavity Type II second-harmonic generation to create an image in the visible spectrum of a target illuminated by an infrared laser. The system has the novelty of being self-illuminated. It uses some fractional leaking power of the infrared laser to illuminate a target located in the object focal plane of the system, and to couple back a created infrared target image to an intracavity nonlinear crystal, where it mixes with the cavity laser beam to obtain a second-harmonic image, visible with a silicon CCD camera. For a proof of concept, we have built a system based on a diode-pumped Nd3+:YVO4 continuous-wave (cw) laser and an intracavity KTP crystal to upconvert 1342 nm target images to 671 nm. The upconverted cw power allowed us to capture real-time video in a standard nonintensified CCD camera, with 2.5 W of a diode pump.