MODE PROPAGATION LOSSES IN HE-IMPLANTED KNBO3 WAVE-GUIDES( ION)

The losses of ion-implanted potassium niobate (KNbO3) waveguides are e valuated theoretically and experimentally in dependence on wavelength, irradiation dose, waveguide thickness, and waveguide width. Irradiati on-induced absorption and tunneling are identified as the main sources of loss. The contributions from surface scattering and intrinsic mate rial absorption are shown to be small. The attenuation due to irradiat ion-induced absorption and tunneling is calculated from the experiment ally determined complex refractive-index profile. The optical loss is minimum in the red part of the spectrum and increases toward the blue because of absorption and toward the infrared because of tunneling. A minimum loss of less than 0.2 cm(-1) (1 dB cm(-1)) was measured in an ion-implanted KNbO3 waveguide at a wavelength of 0.633 mu m. On the ba sis of a theoretical model we give guidelines for the formation of opt imized waveguides for specific applications, e.g., second-harmonic gen eration. (C) 1998 Optical Society of America.