Abstract

In the past decade, poled polymeric materials have been extensively studied for NLO applications since the simplification in preparation and the flexibility exists through chemical synthesis to optimize the physical properties.¹-² Most of the earlier works were concerned with the synthesis and the general properties such as nonlinear optical coefficients and temporal stability and only a few studies have been reported on phase matched second harmonic generation (SHG). In fact, phase-matching is the first important condition to achieve high conversion efficiency of SHG. To realize phasematching, a general method is using the natural birefringence in certain anisotropic crystals to compensate the refractive index dispersions between the fundamental and second harmonic wavelengths and realize $n_{\text{ω}}^2=n_2^2{}_{\text{ω}}$ However, at present, it is not possible to engineer a crystal with the expected birefringence for phase-matching at the required wavelengths. It has been proposed that the mode dispersion and quasi phase-matching for poled polymers. However, these methods are implement from the difficulty in device processing. It was believed that birefringence phase-matching in poled polymers is not possible.³ Nevertheless, through drawing and poling Λ-type main chain polymers, we found phase-matching can be realized at a number of wavelengths. Furthermore, noncritical phase-matching with certain draw ratio is also possible.

© 1995 IEEE