Optical anisotropy in pulsed laser deposited a-GeSe2 thin films

Optical anisotropy was observed by differential polarized optical transmiss ion measurements using polarized 633 nm (sub-bandgap), low incident power ( 0.9 mW) light on a-GeSe2 thin (<0.4 mu m) film samples deposited by laser a blation on silica. Both normal and oblique depositions were studied and no significant difference was found between them. Neglecting the differential absorption at this wavelength, optical anisotropy can arise from birefringe nce. Assuming a simple uniaxial birefringent model, anisotropy axes with a direction change in the 2-15 degrees range were found for each investigated film. Based on this model and considering the multiple reflections in both film and substrate, the difference in refractive index for ordinary and ex traordinary rays was evaluated to be in the 0.005-0.015 range. (C) 1999 Els evier Science B.V. All rights reserved.