Matthias Rottschalk

Single mode integrated-optical wide-band channel waveguides and junction splitters in KTiOPO4 for visible light

Single mode integrated-optical wide-band channel waveguides (SOWCWs) have been defined as a novel type of channel waveguides. The wavelength ranges (bandwidths) of both single mode operation in the channel waveguide and efficient junction-splitting using the same channel waveguides, that is for constant combining or splitting of light in integrated-optical devices like Y junctions, can easily comprise the entire visible wavelength region. In this case, the SOWCW is a real single mode white light channel waveguide. The optical bandwidths of both Rb↔K ion-exchanged channel waveguides in KTiOPO4 (KTP) as an example of SOWCWs and Rb:KTP Y junctions in comparison with those of conventional titanium-indiffused channel waveguides and Y junctions in LiNbO3 have been theoretically calculated and experimentally verified. The channel waveguide attenuation, the coupling efficiency to single mode fibers, and the splitting ratio of Y junctions, especially, show no significant wavelength dependence in the Rb:KTP case. U...

Light-induced refractive index changes in singlemode channel waveguides in KTiOPO4

Abstract Light-induced changes of the effective refractive index in Rb ↔ K ion-exchanged singlemode channel waveguides in KTiOPO4 have been investigated in the visible wavelength region dependent on time, guided optical mode intensity and temperature. A hypothesis for the explanation of the light-induced effects is suggested. Thermooptic and pyroelectric effects are discussed. The light-induced refractive index changes do not restrict the function of integrated-optic components in the visible.

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.

Determination of thermo-optic coefficients in PE: and APE:LiNbO3 channel waveguides for phase-compensated sensor applications

Thermo-optic coefficients of the extraordinary effective refractive index in integrated optical channel waveguides in LiNbO3 have been measured with high accuracy by Mach-Zehnder and Fabry-Perot interferometer techniques. Single mode titanium-indiffused and single mode annealed proton-exchanged (APE) channel waveguides were found to have the same value as it is known for the substrate material. Multimode proton-exchanged (PE) channel waveguides specially designed for maximum field overlap to the APE waveguides show a reduction of the thermo-optic coefficient to one-fifth with negative sign. Phase shift dependent on temperature was examined in APE channel waveguides containing such a strip-shaped multimode PE segment. Possible phase-compensated wavelength sensor applications are proposed.

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.

Multifunction integrated optic circuit for laser Doppler anemometry

An integrated optical device for a two component, dual beam multiplexed laser Doppler anemometer has been realized. The proton exchange and the subsequent annealing procedure in MgO:LiNbO3 yield waveguide structures with completely restored electro-optic effect, low waveguide loss, high coupling efficiency to fibers, and an increased optical damage threshold. In the device for the laser Doppler anemometry the functions of spatial filter, polarizer, beamsplitter and electro-optic modulators are integrated on a single chip. The present paper investigates the use of a specific integrated optical device as a next phase of evolution in laser Doppler anemometry.

Determination of thermooptic coefficients in PE: and APE:LiNbO3 strip waveguides for phase compensated applications

Thermooptic coefficients of the effective refractive index in integrated optical strip waveguides in LiNbO3 have been measured with high accuracy by Mach-Zehnder and Fabry-Perot interferometer techniques. Titanium indiffused and annealed proton exchanged (APE) strip waveguides were found to have the same value as it is known for the substrate material. Multimode proton exchanged (PE) strip waveguides specially designed for maximum field overlap to the APE guides show a reduction of the thermooptic coefficient to one-fifth with negative sign. Phase shift dependent on temperature was examined in APE strip waveguides containing such a strip-shaped multimode PE segment.

Optimization of Ti:LiNbO3 Directional Couplers and Their Application to a Mach-Zehnder Interferometer Modulator

The dependence of the coupling strength of Ti:LiNbO3 directional couplers on fabrication parameters has been investigated. An optical intensity modulator was built up with the couplers.