Jens-Peter Ruske

Integrated-optical wavelength sensor with self-compensation of thermally induced phase shifts by use of a LiNbO3 unbalanced Mach-Zehnder interferometer.

We demonstrate an integrated-optical unbalanced Mach-Zehnder interferometer in lithium niobate for detecting wavelength shifts of light sources, such as laser diodes and superluminescentdiodes at lambda = 844 nm. The output signal can be used to stabilize the light source. Because of the temperature dependence of the effective refractive index and the thermal expansion of the substrate, the device acts also as a temperature sensor. The temperature sensitivity of the interferometer was compensated for by the combination of proton exchanged- and annealed proton exchanged-channel waveguides by approximately two orders of magnitude. The thermo-optic coefficients of the extraordinary effective refractive index in integrated optical channel waveguides in LiNbO8 have been measured with high accuracy over a temperature range from 10 degrees C to 40 degrees C.

Fabrication and characterization of singlemode channel waveguides and modulators in KTiOPO4 for the short visible wavelength region

Singlemode strip waveguides at the wavelengths (lambda) equals0.514 micrometers and (lambda) equals0.488 micrometers have been fabricated in potassium titanyl phosphate (KTiOPO4 or KTP) by rubidium- potassium ion exchange in molten mixtures of RbNO3/KNO3/Ba(NO3)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 (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 Vpi 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.