ALTERNATING LANGMUIR-BLODGETT MULTILAYERS WITH LOW OPTICAL LOSSES FORCERENKOV-TYPE FREQUENCY-DOUBLING

Non-centrosymmetric Langmuir-Blodgett multilayers prepared by alternat e deposition of the non-linear optically active nitrophenylhydrazone a nd an inactive polymer (trimethylsilylcellulose) have a non-linear opt ical susceptibility of 19 pm V-1 independent of film thickness. Optica l waveguides 400 monolayers thick have a quite low damping coefficient of 3.5 dB cm-1 at 63 3 nm. Therefore these multilayers are interestin g candidates for frequency doubling in waveguide configurations. Waveg uides consisting of 120-150 alternating layers were prepared with a hy drodynamic trough on BK7 glass to demonstrate frequency doubling using the Cerenkov effect. The fundamental wave, the light of a Nd Y-Al-gar net laser (1064 nm), was coupled into the waveguide via a prism. The g enerated green light could be observed leaving the substrate through t he substrate edge. To characterize the generated light, the Cerenkov a ngle and the intensity of the second-harmonic beam were measured. The observed Cerenkov angles are in good agreement with theory. From the m easured intensities of the fundamental and second-harmonic waves the c onversion efficienty eta = P2omega/P(omega) was determined to be of th e order of 10(-4).