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 ?= 0.5 14 jtm and ?= 0.488 jtm have been fabricated in potassium titanyl phosphate (KTiOPO4 or KTP) by rubidium-potassium ion exchange in molten mixtures of RbNO3IKNO3IBa(N03)2. The technological parameters had been chosen by means of theoretical calculations concerning the singlemode region of the effective strip waveguide index N00 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 0.5 14 jim. The light-induced refractive index changes (photorefractive effect) have been measured as a function of time, wavelength and optical mode intensity. Electrooptic phase modulators have been succesfully investigated concerning dynamic V, measurements, the electric-optical field overlap and dc-drift phenomena by using an special interferometric set-up based on a two-beam interference of two neighbouring strip waveguides.

Electrooptic Modulators in KTiOPO4 for the Short Visible Wavelength Region

“…The light-induced changes of the effective channel waveguide index are less than 10~5 for output intensities of 10 4 W/cm 2 . All our measurements [10] indicate that the photorefractive effect in t tie KTP channel waveguides is about two orders of magnitude smaller than for annealed protonexchanged waveguides in LiNbO 3 . This is valid for the same guided power and wavelength in the visible.…”

“…10 11 9 Journal of Optical Cor imunicotions Fig. 1 Electric-optical field overlap integral as a function of the electrode gap-width at λ = 0.5145 μπι assuming the single-mode channel waveguide to be placed directly beneath one electrode; the electric and optical parameters for the FEM calculations are specified in the text melt already described proved to be suitable for the realization of the theoretically predicted optical parameters for single-mode operation [10].…”

“…In order to investigate the light-induced refractive index changes as well as the electrooptic phase modulation a special interferometric set-up [10] was used, which is based on the interference of the output beams of two commonly excited neighbouring channel waveguides. The light-or electrooptically induced phase shift takes place in only one of these waveguides.…”