Abstract

Side-chain copolymers are a class of materials for linear and nonlinear optics applications with good structural integrity and stability. However, there are some basic issues that should be addressed in consideration of these materials for device applications. One of the most important questions is what the optical absorption is at 1.3 μm and 1.5 μm. This is particularly important when the materials are used in a waveguide geometry. In this talk, we report the nonresonant optical absorption of several side-chain methacrylate copolymers and polymethylmethacrylate (PMMA) thin films by photothermal deflection spectroscopy (PDS). To understand the optical absorption in the side-chain methacrylate polymers, the absorption spectrum of PMMA thin films was measured by PDS. Several overtone absorption bands due to C-H stretching are identified. The optical window at 1.5 μm has a stronger absorption than that at 1.3 μm because of the stronger overtone absorption at the longer wavelength. Similar to PMMA, overtone absorption bands can also be identified in the side-chain copolymers. Because of the long absorption tail of the chromophore in some side-chain copolymers (for example, silicon naphthalocyanine copolymer), the absorption is larger at 1.3 μm than that at 1.5 μm. The nature of the nonresonant absorption and the possible cause of the absorption tail of these side-chain polymers will be discussed.

© 1992 Optical Society of America