FABRICATION OF LOW-TEMPERATURE PECVD CHANNEL WAVE-GUIDES WITH SIGNIFICANTLY IMPROVED LOSS IN THE 1.50-1.55-MU-M WAVELENGTH RANGE

By excluding nitrogen-containing gases from the deposition process, si lica-based waveguides have been fabricated by PECVD at low temperature with a propagation loss less than 0.2 dB/cm in the 1.50-1.55-mu m wav elength range. PECVD is performed in a high-plasma-density hollow cath ode system from a mixture of oxygen and silane. Carbon tetrafluoride i s used as a fluorine dopant to depress the refractive index in the buf fer and cladding layers. A controllable refractive index change in the range 0.004-0.02 can be obtained.