Orientation patterned GaAs waveguides for parametric conversion from near to mid-infrared have been fabricated by
MOCVD growth on OPGaAs templates. A monolithic OPO cavity was formed by dielectric facet coating. Parametric
oscillation characteristics were investigated using a pulsed source tunable in the range of 1.98-2.05μm. Type I and II
parametric interactions have been observed, differing in QPM wavelength. OPO threshold power of 7W, using a pulsed
pump, and 5.7W using a CW laser was obtained in a 13mm long waveguide of 39μm period. Overall Parametric peak
power of 0.6W at pulsed pump peak power of 11.6W was generated at signal & idler wavelengths of 3.6μm & 4.5μm
respectively and pump wavelength of 2.015μm. Tuning curves for Type I and type II parametric operation in OPGaAs
WGs have been calculated and verified by the measured signal and idler wavelengths.
Material preparation methods and device fabrication technologies for realization of low loss periodically oriented GaAs
waveguides are reported. Planar waveguide structures were grown by MOCVD on periodically patterned templates
prepared by wafer bonding and selective layer removal. Ridge waveguides were designed and fabricated from the planar
structures with emphasis on waveguide loss minimization. Record low losses of 2.0db/cm in periodically oriented
waveguides and 0.95db/cm in single domain waveguides were measured. Routes for further loss reduction in patterned
GaAs waveguides are discussed and initial results from further work to reduce waveguide corrugation are presented.
We present a temperature-dependent Sellmeier equation for congruent and stoichiometric LiTaO<SUB>3</SUB>. The refractive indices in the range of 0.39-4.1 micrometers were determined by scanning the pump lasers wavelength and finding the QPM second harmonic wavelength for a series of period- temperature pairs, and from QPM OPO measurements. The obtained new Sellmeier coefficients were used to calculate the QPM wavelengths of the idler and signal for a PPSLT OPO pumped at 1064 nm. An OPO based on PPSLT was demonstrated. The idler-tuning range was 4.1828-3.9898 micrometers for temperatures of 40-200 degree(s)C. The obtained wavelengths were in good agreement with our predictions.
Frequency conversion efficiency limiting factors in PPKTP crystals and segmented waveguides have been investigated. It was found that at high intensity, back conversion effects related to the spectral and spatial properties of the laser beam, limit the conversion efficiency. High conversion efficiencies in PPKTP are demonstrated by selecting proper laser conditions. A parametric study of the influence of geometrical parameters on conversion efficiency in periodically segmented waveguides has been carried out and an optimal design parameter range has been defined. An improved waveguide structure in which higher efficiencies can be obtained is suggested.
Periodically poled KTiOPO<SUB>4</SUB> (KTP) wafers with short period length are required for generation of green and blue coherent light. Electric field poling processes developed for producing inverted micrometer scale domain structures in other ferro-electric materials cannot be directly applied to flux-grown KTP due to its relatively high (super ionic) conductivity at room temperature. In this paper we describe the low temperature method developed by us for poling flux- grown KTP crystals without modifying their composition. High voltage switching pulses were applied to KTP samples at a temperature below the superionic insulating transition and the switching charge was continuously monitored. This way, high quality domain gratings of 3.8 - 10 micrometers periods were fabricated in 0.5 - 1.0 mm thick flux-grown KTP plates. Second harmonic generation in the range of 400 - 530 nm light by these samples were tested with different types of IR lasers including diode, diode pumped solid state and fiber lasers. The results demonstrate that the low temperature poling technique can provide high quality, short period periodically poled KTP for blue and green coherent light generation.