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Proceedings Paper

Non-collinear upconversion of incoherent light: designing infrared spectrometers and imaging systems
Author(s): Jeppe Seidelin Dam; Qi Hu; Christian Pedersen; Peter Tidemand-Lichtenberg
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Paper Abstract

Upconversion of incoherent mid-infrared radiation to near visible wavelengths, offers very attractive sensitivity compared to conventional means of infrared detection. Incoherent light, focused into a nonlinear crystal, results in noncollinear phase matching of a narrow range of wavelengths for each angle of propagation. Non-collinear phase matching has been an area of limited attention for many years due to inherent incompatibility with tightly focused laser beams typically used for most second order processes in order to achieve acceptable conversion efficiency. The development of periodically poled crystals have allowed for non-critical collinear phase matching of most wavelengths, virtually eliminating the need for non-collinear phase matching. When considering upconversion of thermal light, spectral radiance is limited due to the finite temperature of the Planck radiation source. It is, however, straightforward to increase the incoherent power by increasing the receiving aperture of the upconversion unit i.e. the diameter of the upconversion laser beam. Hence, the optimal conversion efficiency for incoherent light is not achieved by tightly focused beams. In this paper we show that filling the nonlinear crystal with as large a pump beam as possible yields the best conversion as this allows for upconversion of large angles of incoming incoherent light. We present results of non-collinear mixing and how it affects spectral and spatial resolution in the image and compare against experiments. We finally discuss how it can be used to design and predict system performance and how incoherent upconversion can be used for mid-IR spectroscopy and imaging.

Paper Details

Date Published: 20 February 2014
PDF: 7 pages
Proc. SPIE 8964, Nonlinear Frequency Generation and Conversion: Materials, Devices, and Applications XIII, 89640F (20 February 2014); doi: 10.1117/12.2039658
Show Author Affiliations
Jeppe Seidelin Dam, Technical Univ. of Denmark (Denmark)
Qi Hu, Technical Univ. of Denmark (Denmark)
Christian Pedersen, Technical Univ. of Denmark (Denmark)
Peter Tidemand-Lichtenberg, Technical Univ. of Denmark (Denmark)

Published in SPIE Proceedings Vol. 8964:
Nonlinear Frequency Generation and Conversion: Materials, Devices, and Applications XIII
Konstantin L. Vodopyanov, Editor(s)

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