Abstract

Frequency upconversion of the image-bearing light beams which can provide improved image detectability, has been applied recently for imaging through highly scattering media.¹'² Since time gating of picosecond or subpicosecond resolution can be added into the frequency-conversion process, it is possible to make selected detection of the unscattered photons transmitted through the scattering material, which carry the least degraded image information. In particular, image upconversion using coherent anti-Stokes Raman scattering (CARS) has enabled time gating with subpicosecond resolution using long pulse (a few nanoseconds) broadband lasers.^2,3 In these experiments, the image is carried by the Stokes light generated from a Raman cell, and is transferred to anti-Stokes light via another Raman cell. In this paper, we report what is to our knowledge the first demonstration of direct image upconversion from the pump to anti-Stokes beam using stimulated rotational Raman scattering (SRRS) with a polarization-switched pump.

© 1995 IEEE