OPTICALLY ENCODED PHASE-MATCHED 2ND-HARMONIC GENERATION IN SEMICONDUCTOR-MICROCRYSTALLITE-DOPED GLASSES

We observed that the simultaneous injection of the fundamental and second-harmonic fields (1.06-mu-m and 532 nm) into semiconductor-doped glasses results in the evolution of a permanent, quasi-phase-matched, second-harmonic signal that is 10(5) times the initial background value. Using samples as long as 5 cm, we obtained second-harmonic signals that are visible under room lights, corresponding to a conversion efficiency of 10(-6) for mode-locked, Q-switched input pulses. Results are presented for a variety of experiments that shed light on the basic physics of the effect. These include polarization dependence, IR and second-harmonic preparation intensity effects, thermal erasure, and the application of external static-electric fields. The results indicate that the most likely mechanism is the encoding of a periodic internal electric field, which results in a phase-matched electric-field-induced second-harmonic generation process.