August Ferretti

Fabrication and characterization of optical waveguides in KTiOPO4

Planar and channel optical waveguides have been fabricated in KTiOPO4 (KTP) using ion exchange processes. The exchange kinetics are diffusion limited and depend strongly on composition and surface orientation. Increases in surface refractive index of up to 0.23 and waveguide thicknesses of up to 15 μm have been observed. A simple waveguide modulator has been fabricated which shows electro‐optic r coefficients in the waveguide region to be similar to bulk KTP.

Reduction of the ionic conductivity of flux grown KTiOPO4 crystals

Abstract A mechanism and method for reducing the ionic conductivity of KTP crystals grown by the flux technique utilizing the doping of trivalent ions (Ga and A1) on the Ti site and tetravalent ions (Si) on the P site are described. Results are presented showing that, by using appropriate concentrations of these dopants added to the growth solutions, crystals can be grown over a range of growth temperatures which have ionic conductivities that are 1.5 to 3 orders of magnitude lower than undoped KTP crystals grown over similar temperatures. The dopant ion concentrations obtained in the crystals are consistent with the concentrations calculated, using the defect mechanism described, to achieve the observed ionic conductivity reductions. Distribution coefficients have been calculated for the dopants over a wide range of growth temperatures. The distribution coefficient for Ga in KTP appears to be relatively insensitive to concentration or temperature over a range of doping levels and growth temperatures. The use of doping is shown to also be effective in reducing the ionic conductivity of KTA crystals grown by the flux technique.

Proton- and ammonium-exchanged optical waveguides in KTiOPO4

The potassium of KTiOPO4 has been exchanged for protons or ammonium ions to form optical waveguides. Proton exchange is relatively fast, does not give depth profiles expected for diffusive processes, and distinct potassium‐depleted phases are formed. The kinetics for ammonium exchange are relatively slow and diffusion limited, similar to those for Rb and Tl exchange processes. Increases in surface refractive index of up to 0.053 for proton exchange and 0.046 for ammonium exchange have been observed, with higher values for mixed NH4/H and Rb/H exchanges.

KTiOPO4 (KTP): A New Material for Optical Waveguide Applications

KTP is a unique nonlinear optical material that is widely used for second harmonic generation of Nd:YAG. It also has high electrooptic coefficients and low dielectric constants that together with its high optical damage thresholds and high thermal stability make KTP superior for integrated optical applications as well.

Gray-track damage in KTiOPO4 crystals

A correlation is observed between the laser and electric-field damage susceptibilities of most KTiOPO4 (KTP) crystals. The observed gray track damage susceptibilities are found to be correlated to the concentrations of defects in the crystals which can stabilize the Ti3+ damage defect sites in KTP. These stabilizing defects are those which can have an effective positive charge, such as oxygen vacancies, protons, and Ba and F impurities. The defects present in KTP crystals depend on the technique (hydrothermal or flux) used for growth. Post-growth processing techniques have been developed which reduce the laser gray track and electric-field damage susceptibilities of both hydrothermal and flux KTP.

KTiOPO4:(KTP): A New And Superior Electrooptic Material For Guided Wave Optics

Electrooptic modulation is the changing of the phase or amplitude of an optical beam by an applied electric field. This phenomenon is inherently nonlinear and can only be observed in crystals that do not have an inversion symmetry. The modulation, when effected in a waveguide, is the foundation of many guided wave optical devices, such as: Mach-tender interferometers, channel switches and directional couplers, etc. which are particularly useful for fiber optics communication)