Moshe Oron

Highly efficient doubling of a high-repetition-rate diode-pumped laser with bulk periodically poled KTP.

An internal doubling efficiency of 64% at 2 MW/cm(2)was obtained in a single-pass configuration with an uncoated, 1-cm-long, bulk periodically poled KTP crystal placed outside the resonator of a pulsed, diode-pumped Nd:YAG laser. An average of 4.8W of green light was obtained from a 7.5-W pump beam inside the crystal. Doubling efficiency exceeded 50% at levels of 0.75 MW/cm(2). The measured thermal tolerance of the doubling process (FWHM) was 3.3( degrees )C cm, and the measured temperature tuning coefficient was 0.053 nm/( degrees )C .

Efficient resonant frequency doubling of a cw Nd:YAG laser in bulk periodically poled KTiOPO(4).

A cw Nd:YAG laser was quasi-phase-matched frequency doubled by a bulk periodically poled flux-grown KTiOPO(4) crystal in an external resonant cavity. The conversion efficiency and the second-harmonic power with a pump of 225 mW were 55% and 123.5 mW, respectively. The loss of the 1-cm-long crystal, which operated near room temperature, was 1.3% and was dominated by scatter from the cleaved facets of the crystal. No damage, photorefractive or other, was observed at intensites of 370Wmm(-2) , but beam size had to be optimized to eliminate thermal-induced instabilities in the doubling cavity.

Second-harmonic generation in Bragg-resonant quasi-phase-matched periodically segmented waveguides

Second-harmonic generation in Bragg-resonant quasi-phase-matched periodically segmented waveguides is studied experimentally and theoretically. At resonance, a deep spectral valley appears in the quasi-phase-matching curve. Nevertheless, in practice, the conversion efficiency is significant, in spite of this effect, because of reduced reflections, especially at 2omega. The mechanism behind this reduction seems to be small random variation in the location and shape of the domain boundaries.

Fast switching of drift step recovery diodes based on all epi-Si growth

DSRDs are fast HV opening switching devices. Traditionally, these deep junction devices are fabricated on silicon wafers by deep diffusion. We present DSRD results based on silicon epitaxial layers with as-grown junctions. Static measurements showed a rectifying behavior with leakage currents proportional to device dimension. Pulsed power measurements showed that the switching rate was dependant on the DSRD current density.

Efficient second-harmonic generation and modal dispersion effects in orientation-patterned GaAs waveguides

Efficient second-harmonic conversion of 4 microm radiation was demonstrated in orientation-patterned GaAs (OPGaAs) waveguides (WGs). An experimentally corrected phase-matching curve for second harmonic generation (SHG) in OPGaAs WGs is presented. Influence of WG modes on the SHG process was studied. Two distinct types of SHG in the waveguides were identified and related to the TE and TM modes. Each type has its own dependence on pump polarization. The 21% W(-1) normalized conversion efficiency is within a factor of 0.75 from the predicted value for an ideal WG.

Refractive index dispersion measurements of congruent and stoichiometric LiTaO 3

We present a temperature-dependent Sellmeier equation for congruent and stoichiometric LiTaO3. 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 limitation in periodically poled KTP crystals and waveguides

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.

Frequency doubling in periodically poled flux-grown KTP of short period length

Periodically poled KTiOPO4 (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.

High Efficiency Mid-IR Second Harmonic Generation in Orientation Patterned GaAs Waveguides

21%W-1SHG efficiency at 4?m was demonstrated in OPGaAs waveguides. The high efficiency is attributed to record low waveguide loss of 1.0db/cm, high material quality periodically grown structure and accurate modeling of waveguide effective indices.