2ND-HARMONIC GENERATION AS A NONDESTRUCTIVE READOUT OF OPTICAL (PHOTO(ELECTRO)CHROMIC AND MAGNETIC) MEMORIES

Optical second harmonic generation (SHG) is suggested as a nonlinear-o ptical nondestructive readout of (thin) film-based optical memories. S ystematic studies of photoinduced, electroinduced, and magnetoinduccd variations in the anisotropic SI-IG intensity in (i) thin solid photo( electro)chromic films of bacteriorhodopsin, (ii) photosensitive Langmu ir-Blodgett films of 4-nitro-4'-N-ocradecylazobenzene, and (iii) rare- earth iron garnet films show sufficient modification of their nonlinea r-optical properties by these external factors. These photo-, electro- and magnetomodified nonlinear-optical properties of thin films being used for recording the information can be easily distinguished by the SHG readout. The IR fundamental radiation used for the excitation of t he SHG is shown not to disturb the information recorded in photo(elect ro)chromic memories. For, what is to our knowledge, the first time, th e surface-bulk crossterms in the SHG intensity originating from the in terference of the crystalline and magnetization induced second harmoni c fields are observed in magnetic iron garnet films.