2X2 SINGLE-MODE ZERO-GAP DIRECTIONAL-COUPLER THERMOOPTIC WAVE-GUIDE SWITCH ON GLASS

A 2 x 2 single-mode thermo-optic waveguide switch fabricated on a glas s substrate is reported. The device uses a zero-gap directional-couple r configuration with a heater electrode to increase the waveguide inde x of refraction by the use of the thermo-optic effect. With an interac tion length of 6 mm and using 0.63-mum He-Ne laser light, the device e xperiences a complete switchover of light from a straight-through chan nel to a crossed channel at an electrical drive power of 0.25 W under a quasi-steady-state condition and 0.67 W under a pulsed condition of 800 mus in pulse width. The device response is independent of light po larization and insensitive to ambient temperature. Transient thermal a nalysis is carried out with a two-dimensional transient temperature so lution derived previously [IEEE Trans. Components Hybrids Manuf. Techn ol. 13, 1990)]. A thermo-optic equation is established to relate the o ptical intensity to the temperature rise in the waveguide. The deduced optical responses based on the thermo-optic equation and the calculat ed thermal response agree extremely well the measured responses, thus verifying the thermo-optic equation and the thermal-analysis method. W e also confirm the fundamental principle of the zero-gap directional c oupler and find that the 2 x 2 single-mode switch will be a useful com ponent in future fiber-optic and integrated-optic systems.