Optical absorption and scattering losses of PTS and poly(4-BCMU) thin-film waveguides in the near infrared

Abstract

The relative suitability of the organic polymers poly[5,7-dodecadiyn-1,12-diol-bis(n-butoxycarbonylmethylure-thane)] [poly(4-BCMU)] and poly[2,4-hexadiyn-1,6-diol-bis(p-toluenesulfonate)] (PTS) for fabricating low-loss nonlinear-optical waveguides was evaluated. Several-centimeter-long amorphous poly(4-BCMU) thin-film slab waveguides were easily fabricated by spin-coating techniques. The loss for these waveguides at 0.83 μm was estimated from intensity measurements of propagating light scattered from the waveguide surface. The observed scattering losses varied from less than 20 dB/cm to more than 20 dB/cm. The measured intrinsic absorption loss of poly(4-BCMU) was found to be less than 0.1 cm⁻¹ in the infrared and was not expected to add greater than a 1-dB/cm power loss to a waveguide. 1–3-mm-long anisotropic, crystalline PTS thin-film slab waveguides were prepared by solution shear methods and showed negligible scattering losses at 0.83 μm. The measured intrinsic absorption in PTS varies from 2 cm⁻¹ at 0.83 μm to less than 1 cm⁻¹ at greater than 1 μm and may cause the directly measured power loss in PTS waveguides to be no more than 8 dB/cm.