PHOTOELASTIC WAVE-GUIDES FORMED BY INTERFACIAL REACTIONS

The fabrication of low-loss photoelastic waveguides in GaAs/A]GaAs lay ered structures by thin film reactions is investigated. The waveguides are formed by opening a narrow window stripe, a few microns wide, in an otherwise continuous Ni layer under tension deposited on a semicond uctor structure. The local tensile stress induced by the Ni layer in t he semiconductor causes the local refractive index to increase, thus p roviding the guiding mechanism. Annealing the sample at 250-degrees-C for 1 h induced an interfacial reaction between the Ni film and the su bstrate to form Ni3GaAs. The formation of an interfacial compound stab ilizes the stresses, making the stress state independent of the deposi tion system and technique. Single-mode waveguide propagation losses as low as 1.4 dB/cm at 1.53 mum wavelength have been obtained on anneale d waveguides. Further annealing up to 600-degrees-C did not cause degr adation in the optical confinement, thus indicating a thermally stable planar waveguide fabricated by this process. Other photoelastic optic al devices such as polarizers, splitters, and couplers are also demons trated.