Fabrication and characterization of singlemode channel waveguides and modulators in KTiOPO 4 for the short visible wavelength region

Abstract

Singlemode strip waveguides at the wavelengths (lambda) equals0.514 micrometers and (lambda) equals0.488 micrometers have been fabricated in potassium titanyl phosphate (KTiOPO<SUB>4</SUB> or KTP) by rubidium- potassium ion exchange in molten mixtures of RbNO<SUB>3</SUB>/KNO<SUB>3</SUB>/Ba(NO<SUB>3</SUB>)<SUB>2</SUB>. The technological parameters had been chosen by means of theoretical calculations concerning the singlemode region of the effective strip waveguide index N<SUB>00</SUB> at the given wavelength. Measured near field distributions and insertion losses of the strip waveguides led to a typical attenuation of about 2 dB/cm for TM polarization at (lambda) equals0.514 micrometers . The light-induced refractive index changes (photorefractive effect) have been measured as a function of time, wavelength, and optical mode intensity. Electro-optic phase modulators have been successfully investigated concerning dynamic V<SUB>pi</SUB> measurements, the electric-optical field overlap and dc-drift phenomena by using a special interferometric setup based on a two-beam interference of two neighboring strip waveguides.