Second-harmonic generation from Z-type Langmuir-Blodgett films of a transparent dye and a comparison of the properties when the layers are interleaved with poly(t-butyl methacrylate)

Geoffrey J. Ashwell; Rakesh Ranjan

doi:10.1117/12.328563

29 October 1998 Second-harmonic generation from Z-type Langmuir-Blodgett films of a transparent dye and a comparison of the properties when the layers are interleaved with poly(t-butyl methacrylate)

Geoffrey J. Ashwell, Rakesh Ranjan

Author Affiliations +

Proceedings Volume 3474, Second-Order Organic Nonlinear Optics; (1998) https://doi.org/10.1117/12.328563
Event: SPIE's International Symposium on Optical Science, Engineering, and Instrumentation, 1998, San Diego, CA, United States

Abstract

The Langmuir-Blodgett (LB) film structure of E-4-[(N- octadecyl-6,7,8-trihydro-5-isoquinolylidene)methyl]-N,N- dibutylaniline octadecylsulfate is non-centrosymmetric when the dye is deposited on the up-stroke (Z-type) and when the layers are interleaved with poly(t-butyl methacrylate). The second-harmonic intensity increases as I_(N)^2(omega ) equals I₍₁)^2(omega )N², where N is the number of active layers, and the intensity is further enhanced when the dye is mixed in a 1 to 1 ratio with octadecanoic acid. The second-order susceptibility and repeat lattice spacing of the mixed LB films are as follows: (chi) _zzz⁽²) equals 76 pm V^-1 at 1.064 micrometers and l equals 3.15 nm layer^-1 when Z-type; (chi) _zzz⁽²) equals 52 pm V^-1 and l equals 4.13 nm bilayer^-1 when interleaved. The films are transparent at the fundamental wavelength and have a slight absorbance of ca. 5 X 10^-4 per dye layer at 532 nm. The second-harmonic intensity is the strongest to date from such a weakly absorbing LB film and this is attributed to the close proximity of the charge-transfer band and to an optimized packing arrangement.

Citation Download Citation

Geoffrey J. Ashwell and Rakesh Ranjan "Second-harmonic generation from Z-type Langmuir-Blodgett films of a transparent dye and a comparison of the properties when the layers are interleaved with poly(t-butyl methacrylate)", Proc. SPIE 3474, Second-Order Organic Nonlinear Optics, (29 October 1998); https://doi.org/10.1117/12.328563

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