Upconversion spectral response tailoring using fanout QPM structures

In this Letter, a novel technique for independent control of the phase-matched center wavelength and bandwidth (BW) is demonstrated for upconversion detection in the 2–4 μm range using a fanout lithium niobate (LN) crystal. A compact, all-semiconductor, 975 nm laser delivering 3.5 W of power is used as the pump in a single-pass upconversion configuration. A globar (∼800°C) is used as the infrared test source. Continuous tuning of the detected wavelength (λ_c:2.5–3.0 μm) and BW (Δλ_IR:35–225 nm) has been realized using mechanical translation and rotation, respectively, of the fanout LN crystal. A comparison between the performance of the fanout LN and a conventional periodically poled LN crystal is made. The upconverted light is detected using a commercial silicon-spectrometer. The demonstrated technique allows tailored spectral upconversion based on collinear interaction. Numerical simulations are made to complement the experimental results.