[OPTICAL REVIEW Vol. 4, No. 5 (1997) 553-555]
Comparison of Bistable Light Emission of a Thin CdS:Cu Film Measured in Reflection and Transmission Geometry
Bruno ULLRICH, Mitsuhito SASAKI and Takayoshi KOBAYASHI
Department of Physics, University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo, 113 Japan
(Received September 14, 1996; Accepted July 8, 1997)
All-optical photo-thermally induced bistabilities in luminescence of a thin (10 μm) CdS:Cu film were studied at 170 K. The bistable effect was induced by the 514.5 nm line of an argon laser and measured by putting low-pass filters for yellow and red light in the reflected and transmitted beams. In the visible part of the spectrum, the loop contrasts measured in reflection geometry are considerably smaller than those achieved in transmission geometry. In the near infrared, however, the loop contrasts do not depend on the geometry used. This is due to the observation that visible emissions from the surface region depend less sensitively on temperature than do those from the bulk.
Key words : all-optical bistability, bistable luminescent effect, bistable reflectance, thin films, II-III compounds