Phase-matched Generation Research Articles

Updated thermo-optic coefficients of AgGaS^2 from temperature-tuned noncritical 3ω ω → 2ω infrared parametric amplification

We report the temperature dependence of a continuous-wave noncritically phase-matched (θ=90°) optical parametric amplifier based on a 15-mm-long silver gallium sulfide crystal (AgGaS2) pumped by a 50-mW near-IR AlGaAs diode laser (λ3=0.843 µm). This amplifier is idler seeded by a 15-mW KCl:Li (FA-II) color-center laser (λ1=2.53 µm) and produces microwatt-range power of a signal radiation at λ2=1.265 µm. Updated linear and thermo-optic data of this chalcopyrite material, such as its room-temperature refractive indices and their temperature dependence, are devised from this type I (eoo) 3:1 frequency-division process and from other published data on noncritically phase-matched difference-frequency generation. The resulting dno,e/dT values reproduce fairly well all of the reported results on temperature phase-matched parametric mixing.

Efficient generation of CW blue light by sum-frequency mixing of laser diodes in KNbO 3

A tunable continuous-wave diode-pumped blue laser is demonstrated by noncritical type I phase-matched sum-frequency generation in a potassium niobate (KNbO 3) crystal. A maximum output power of 65 mW of nearly diffraction-limited light at 434.7 nm is generated in a 14.5 mm long crystal by mixing a 982.6 nm master-oscillator power-amplifier InGaAs laser diode and a 779.5 nm AlGaAs laser diode with an overall conversion efficiency of 7.2%/W. The blue laser is continuously tunable over the wavelength range from 432 to 438 nm.

Nonlinear laser crystal as a blue converter: laser heated pedestal growth, spectroscopic properties and second harmonic generation of pure and -doped single crystal fibres

The study of pure and -doped single crystal fibres with x = 0.24 by the LHPG technique is reported. The wavelength for non-critical second harmonic generation phase matching was found to be near 932 nm. Low-temperature spectroscopy reveals that the ions are located in the A2 sites of the tungsten - bronze structure in different environments. The stimulated emission cross section near 1060 nm of the channel and its branching ratio are determined with the help of the Judd - Ofelt analysis.

90° phase-matched ultraviolet generation at 0.2660 μm in LiClO4⋅3H2O

LiClO4⋅3H2O has been found to be 90° phase-matchable for ultraviolet generation at 0.2660 μm at a crystal temperature of 30.6 °C. A peak power as high as 28 MW with an average power of 2.2 W was obtained in a 1.5-cm-long crystal. Sellmeier’s equations and nonlinear constant of this crystal are reported.

Phase-matched UV generation at 01774 μm in KB_5O_8 · 4H_2O

Sixth-harmonic generation of the Nd:YAG laser frequency at 1.0642 μm has been achieved in KB(5) O(8) ˙ 4H(2) O by type-1 mixing the fundamental and fifth harmonic at room temperature. The phase-matching angles were measured to be (θ = 90°, φ = 68.5 ± 0.5°) and (θ = 80.0 ± 0.5 °, φ = 90°) in the x - y and y -z planes, respectively. Improved Sellmeier equations of this crystal are presented.

Frequency upconversion by phase-matched sum-frequency generation in an optical parametric oscillator

We report the generation of 0.589-,microm radiation from mixing the pump at 1.064 ,microm and the signal at 1.319 microm of a singly resonant, synchronously pumped AgGaS(2) optical parametric oscillator. A KTP crystal is used for the sum-frequency generation (SFG). Both extracavity and intracavity SFG is demonstrated, with overall conversion efficiencies of 3.5% and 10.5%, respectively. Near-transform-limited pulses of less than 50 ps are generated from 100-ps pulses. With a limited available peak pump power, both spatial orderings of the KTP and the AgGaS(2) crystals for intracavity SFG produce similar conversion efficiency and outputs of similar pulse duration, spectral width, and stability.

Spectral noncritically phase-matched near-infrared generation by difference frequency mixing in lithium triborate

Retracing behavior of phase matching has been observed in the generation of infrared radiation (1.25–1.85 μm) by both type-I angle-tuned and temperature-tuned difference frequency mixing of a Nd:YAG laser (1064 nm) with its second-harmonic pumped dye laser (570–675 nm) in lithium triborate crystal. Large spectral acceptance of 49 nm at spectral noncritical phase-matching point and angular acceptance of 4.0° at angular noncritical phase-matching point has been obtained.

Conversion of the frequency of laser radiation in lithium triborate LiB3O5crystals

Optical and nonlinear optical properties of LiB3O5 single crystals grown from a molten solution were investigated. Experiments yielded the directions along which phase-matched generation of the second and third harmonics of garnet laser radiation was possible. The parameters of generation of the second harmonic of YAG laser radiation were determined at room temperature and at a temperature of noncritical phase matching. The experimental results were used to determine the mutual orientation of crystallographic and crystallophysical coordinate systems.

Phase-matched harmonic generation in lithium triborate (LBO)

The authors present refractive index, thermo-optic, phase-matching angle, nonlinear coefficient, absorption, and scattering data on lithium triborate (LBO) crystals. They briefly discuss the material quality of the crystals, including the results of calorimetric absorption measurements in the infrared and ultraviolet. They present a new set of refractive index values with better than fourth decimal place precision, as well as measurements of the thermo-optic parameters. The nonlinear coefficients and other frequency conversion parameters of LBO were investigated by studying the phase-matched generation of Nd:YAG harmonics. These results are summarized. The authors discuss angular and thermal bandwidths for phase matching. Finally, they compare the efficiency of LBO with that of several other frequency conversion crystals for a common commercial application-the generation of Nd:YAG harmonics.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Growth of beta-barium metaborate single crystal fibers along the phase matching direction

High optical quality single crystal fibers of β-BaB2O4 (BBO), an important nonlinear optical material, were grown along the second-harmonic generation phase matching direction by the laser heated pedestal growth method. The effects of various growth parameters, especially growth rate, on growth stability and fiber quality were investigated. It was found that 0.25mm/min is the suitable growth rate which can reduces the harmful effects of growth anisotropy and constitutional supercooling on fiber quality.

Picosecond third-harmonic light generation in calcite

The third-harmonic generation of picosecond light pulses in a calcite crystal is studied experimentally and theoretically. A passively mode-locked Nd: phosphate glass laser is used in the experiments. The third-order nonlinear susceptibility components and the effective third-order nonlinear susceptibility of type II phase-matched (ooe→e) thirdharmodic generation are determined.

Phase-matched frequency tripling and phase conjugation in isotropic materials

A new phase-matching scheme for noncollinearly phase-matched fifth-order difference-frequency generation (FODGE), yielding the third harmonic, is described. The coupled-wave equations are solved for some special cases, and the phase-conjugating properties of FODGE are discussed. Different causes of phase mismatch are also discussed.

Second-harmonic generation in an optical fibre by self-written χ (2) grating

A mechanism for phase-matched generation of second-harmonic (SH) light in an optical fibre has been experimentally and theoretically studied. A weak non-phase-matched SH signal, created via the quadrupole polarisation, initiates the self-writing of an axially periodic pattern of colour centres which is postulated to lead to the growth of a χ (2) grating. The grating (at the phase-match period) gives rise to SH generation at efficiencies of 0.5%. The spectral bandwidth of this χ (2) grating is 0.24 nm.

Polychromatic phase conjugation with noncollinearly phase-matched difference-frequency generation

A new geometry for third-order nonlinear, noncollinear difference-frequency generation is presented and experimentally verified. It is shown to be equal to a polychromatic phase conjugation. The coupled-wave equations are solved for steady-state cw pumping and for transient pumping without reconjugation. Applications to image processing and to tunable generation of coherent light are discussed.

A Study of a Ferroelectric Liquid Crystal Using Second Optical Harmonic Generation

Abstract The phase-matched generation of the optical second harmonic was investigated in the chiral smectic C* phase of a classical ferroelectric liquid crystal (DOBAMBC). The phase-matching was achieved either by incidence angle or by temperature tuning. The temperature behaviour of the second order nonlinear susceptibility was studied.

Nearly noncritically phase-matched UV generation at 3547 Å in NaCHO&amp;lt;inf&amp;gt;2&amp;lt;/inf&amp;gt;

Sodium formate (NaCHO 2 ) has been found to be very nearly noncritically phase matchable for type-2 frequency mixing of the Nd:YAG laser fundamental and second-harmonic radiation at room temperature. The nonlinear optical constant was determined to be d 32 (NaCHO 2 ) = (1.25 \pm 0.25) \times 10^{-9} ESU.

Li In- and Out-Diffusion Processes in LiNbO3

Li in-diffusion and out-diffusion processes in LiNbO3 crystals, when treated in Li2CO3 powder, were investigated through second harmonic generation phase matching temperature measurement using a YAG laser. After annealing at 600°C for more than 52 hours in Li2CO3, in-diffused Li ions caused a slight decrease in the ordinary refractive index near the surface of the polished LiNbO3 substrate. These samples showed a large decrease in extraordinary refractive index after being annealed at 1050°C in air. Wrapping the LiNbO3 substrate in platinum foil to prevent direct contact with the Li2CO3 powder was found to be a successful method to suppress Li out-diffusion without surface degradation.

Noncollinear phase-matched four-photon mixing of CO 2 laser radiation in germanium

Noncollinear four photon mixing of two TEA CO 2 laser beams in germanium at room temperature has been used to obtain phase-matched generation of step tunable radiation in the 8.7 μm region which is of interest for the uranium isotope separation. Using an 8.3 cm long crystal of germanium, peak output power of ≈10kW (corresponding to 1 mJ per pulse) was obtained at 8.7 μm with 3 MW peak input power from each of the two CO 2 lasers operating at 9.6 μm and 10.6 μm.

Phase-matched generation of 2314 Å in KB5O8⋅4 H2O

Third-harmonic generation of a ruby laser has been achieved in a potassium pentaborate tetrahydrate (KB5O8⋅4 H2O) crystal through type-1 frequency mixing of the fundamental and second-harmonic radiation. An over-all power conversion efficiency of 0.2% was obtained.

Phase transitions in Cs(DxH1-x)2AsO4

Three phase transitions were observed in single crystals of Cs(DxH1-x)2AsO4. Two of these transitions are predicted from the double minimum potential well theory of hydrogen-bonded ferroelectrics and are associated with the ferro-electric-paraelectric transition (227°K) and the melting or decomposition temperature (467° K) of the crystal. A third transition was observed at 443° K which is destructive. The behavior at this transition was investigated by DTA, TGA and X-ray diffraction techniques. The variation of the ferroelectric transition and optical (SHG) second harmonic generation phase matching temperatures was found to be a linear function of deuteration.