Second Harmonic Generation in Multilayer Langmuir−Blodgett Films of Blue Transparent Organic Polymers

Multilayer Langmuir−Blodgett (LB) films were fabricated with two
blue transparent nonlinear optical
polymers in which the orientation of the nonlinear optical chromophore
in one polymer is reversed with respect to
the other. The intensity of the frequency-doubled light generated
in these multilayers increases quadratically, with
the increasing number of bilayers indicating that the macroscopic
optical nonlinearity, χ(2), of the bilayer is a
linear
sum of the macroscopic optical nonlinearities of the individual
monolayer. Also, multilayer LB films of each blue
transparent polymer were made by alternate deposition with a spacer
polymer, poly(tert-butyl methacrylate).
The
intensity of the frequency-doubled light generated by these multilayer
films was approximately 4 times smaller than
that generated by multilayer films of two blue transparent polymers
with the same number of layers, indicating that
the use of another nonlinear optical active polymer in the place of
passive poly(tert-butyl methacrylate)
polymer
leads to considerable improvement in the frequency-doubling efficiency.
Multilayer LB films of these polymers
show a great potential for achieving a practical level of
performance.