Abstract

Using 30-psec pulses from a frequency doubled Nd:YAG laser, we have amplified and detected images with a resolution of less than 300 μm through suspensions of latex spheres and non-dairy creamer with nonscattered extinction ratios of up to e^-40. Our time-gated image amplifier can produce images under conditions in which the scattering medium is sufficiently dense that an image cannot be seen on either a streak camera or through a long-time integration on a CCD camera. The 532-nm frequency-doubled output was used both to generate a seed-Stokes pulse at 683 nm using hydrogen at 30 atm and to pump the 1-m long Raman amplifier.¹ The seed-Stokes light was used to illuminate a bar chart of line spacing 0.315 mm placed immediately before a cell containing the scattering medium. The direct image, or its Fourier transform, was amplified in the Raman amplifier. The original bar chart image was then observed using an intensified camera. By using a delay to vary the time of arrival of the pump pulse at the amplifier we were able to selectively amplify the image-bearing component at the front of the pulse and so discriminate against the multiply scattered light which can extend out for many pulse durations.

© 1991 Optical Society of America