A. Skliar

Tunable midinfrared source by difference frequency generation in bulk periodically poled KTiOPO4

We demonstrate quasi-phase-matched difference frequency generation in periodically poled KTiOPO4. A midinfrared (3.2–3.4 μm) idler with a power level of 0.17 μW is generated by mixing a Nd:YAG laser and tunable external cavity laser near 1550 nm which is amplified by an erbium-doped fiber amplifier. The wavelength, temperature, and angle tuning characteristics of this device are determined. The experimental results are used to derive a Sellmeier equation with improved accuracy in the midinfrared range for the extraordinary refractive index of flux-grown KTiOPO4.

Low temperature periodic electrical poling of flux-grown KTiOPO4 and isomorphic crystals

Studies of dielectric spectroscopy, dc conductivity, and polarization switching allowed the observation of phase transition from the superionic to the insulating state in flux-grown KTiOPO4 (KTP) crystals at low temperature where the high mobility of potassium ions is suppressed. A low temperature method of fabrication of engineered periodic domain structures in superionic KTP and isomorphic crystals is proposed. It enabled us to tailor homogeneous domain gratings with various periods in the range 4–39 μm for quasiphase-matched nonlinear optical converters in KTP plates over whole area of 30×30 mm2.

Nondestructive imaging and characterization of ferroelectric domains in periodically poled crystals

We report the nondestructive investigation and visualization of periodically poled domains in ferroelectric potassium titanyl phosphate (KTP) crystals using polarization sensitive scanning force microscopy (SFM). Applying an alternating voltage technique to SFM allows ferroelectric domain wall resolution beyond 100 nm. Image contrast between KTP and Rb doped KTP, i.e., rubidium titanyl phosphate (RTP) regions arises from the differential piezoelectric response. We find the polarization vectors in both KTP and RTP to be aligned parallel to the negative z axes as deduced (a) when comparing our data with a ferroelectric reference sample, i.e., tri-glycine sulfate (b) from comparison of nanoscale hysteresis loops recorded on KTP and RTP, and (c) from direct domain switching in KTP applying very high electric fields between tip and counter electrode. The latter experiments show that nanoscale ferroelectric domains in KTP switch from the negative to the positive z-axes alignment for electric fields stronger tha...

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 .

Green and ultraviolet quasi-phase-matched second harmonic generation in bulk periodically-poled KTiOPO4

Abstract A periodically-poled flux-grown KTP crystal was used for first order quasi-phase-matched (QPM) second harmonic generation of a Nd:YAG laser. The normalized conversion efficiency of the 1 cm long, 0.5 mm thick sample was 1.28% W −1 . A lower limit on the nonlinear coefficient of KTP, d 33 ≥ 14.9 ± 1.5 pm/V was derived from these measurements. The temperature and wavelength tuning coefficients near 1064 nm were determined. The same device was also used for third order QPM frequency doubling of 784 nm light, and the normalized conversion efficiency in this case was 0.12% W −1 .

Domain broadening in quasi-phase-matched nonlinear optical devices

Dominant factors influencing domain broadening in periodically poled ferroelectric domain structures for quasi-phase-matched nonlinear optical converters are studied. It is shown that fabricated patterned switching electrode gives rise to a high tangential field causing polarization inversion behind an isolated layer of the patterned electrode. The domain broadening depends on basic electron parameters of a ferroelectric crystal such as surface electron concentration and electron mobility.

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.

Continuous-wave optical parametric oscillator based on periodically poled KTiOPO 4

We report what is to our knowledge the first demonstration of a continuous-wave optical parametric oscillator (OPO) based on periodically poled KTiOPO(4) . The 10-mm-long flux-grown crystal had a quasi-phase-matched period of 9mum . The pump source was a miniature frequency-doubled Nd:YAG laser, and the threshold power of this doubly resonant device was 51 mW. The OPO was operated near room temperature. The signal and the idler wavelengths could be tuned in the range 1037-1093 nm by variation of the crystal temperature (32-38 degrees C) and the cavity length. Unlike in other nonlinear crystals, green-induced infrared absorption was not observed up to the highest pumping intensity of approximately 4.5kW/cm(2) .

Polarization reversal in crystals

Characteristics of spontaneous polarization reversal have been studied in detail for the first time in crystals subjected to a pulsed electric field in the range 15 - 70 kV . The switching process has been observed by recording a transient switching current and subsequent piezoelectric probe mapping and optical and secondary electron microscopy methods. The measured value of spontaneous polarization is . The ionic potassium DC current was observed to have a strong effect on the polarization switching. The developed experimental set-up has made it possible to fabricate a periodic domain structure and to generate an optical second harmonic power.

Ferroelectric electron emission flat panel display

Ferroelectric electron emission observed under periodic spontaneous polarization switching is the basis for the development of a new type of flat panel display. Electron emission occurs from individually operated ferroelectric domains. It is shown that ferroelectric displays may be fabricated in ‘‘plane‐to‐plane’’ geometry which is not possible for field emission displays.