OBSERVATION OF AN OPTICAL-MODULATION EFFECT ON 2ND-HARMONIC GENERATION IN C-60 THIN-FILMS

We report optical modulation effects on second harmonic generation (SH G) in C-60 films. It was observed that a large second harmonic respons e of C-60 films (in a corona poling field of 5.5 kV at a nominal tempe rature of 140 degrees C) was almost completely suppressed when the fil m was illuminated with a second visible-light source (pulsed or steady state). The magnitude of the SHG suppression was measured as a functi on of the wavelength and intensity of the second source. By scanning t he time interval between a ''suppression'' pulse and the SHG generatio n pulse we found that the lead time required for the suppression effec t is about 250 ps.