Phase-matched Frequency Doubling Research Articles

Efficient second-harmonic generation by lens wave-guiding in KNbO3 crystals

A novel configuration of lens waveguiding in a cascade of nonlinear optical crystals is proposed whereby the conversion efficiency increases quadratically with the interaction length. 17 mW of continuous-wave blue light at 428.5 nm and 35 mW at 490.8 nm is generated by noncritical type I phase-matched frequency doubling of near infrared laser diodes in a cascade of two and three potassium niobate (KNbO3) crystals, respectively.

Nonlinear dynamics of a backward quasi-phase-matched second-harmonic generator

We study the stability of the interaction between a pump wave and a counter propagating second-harmonic wave phase-matched in a periodically poled ${\mathrm{\ensuremath{\chi}}}^{(2)}$ material using both analytical and numerical methods. In contrast to the more usual copropagating case, backward phase-matched frequency doubling displays richer and more complex behavior, owing to the presence of built-in feedback.

New nonlinear-optical organic crystal: 4-dimethyl-aminobenzaldehyde- 4-nitrophenyl-hydrazone

Single crystals of 4-dimethylaminobenzaldehyde-4-nitrophenylhydrazone were grown from solution. We determined their linear-optical (absorption and refractive indices) as well as their nonlinear-optical properties. From the highest nonlinear-optical coefficient d12=270 pm/V at λ=1.542µm we determine an effective nonlinear-optical coefficient deff⩾150 pm/V for phase-matched frequency doubling that is, to the best of our knowledge, the largest reported phase-matchable coefficient. The nonlinear-optical properties are discussed in terms of the crystal structure and the molecular hyperpolarizabilities. In addition, the phase-matching configurations for second-harmonic generation and optic parametric oscillation are derived.

Second-order nonlinear optical properties from poled silicate channel-waveguide

Thin film waveguides of germanosilicate glass are fabricated byrf-sputtering. Second-order nonlinearity ofd33=3.2 pm/V is obtained from electrically poled film, and the lifetime of the nonlinearity is found to be310 years. The poled channel-waveguide is prepared and the Cerenkov-type phase-matched frequency doubling is successfully observed.

Growth and characterization of K3Li2(TaxNb1−x)5O15 crystals for blue second-harmonic-generation applications

Potassium lithium tantalate niobate, K3Li2(TaxNb1−x)5O15, or KLTN single crystals were grown by spontaneous crystallization method, and it has been demonstrated that the KLTN crystal has high potential as a nonlinear crystal for blue second-harmonic-generation (SHG) applications. Ta substitution for Nb site in K3Li2Nb5O15 crystal improves the transparency in the blue light region and decolorizes the material. Compared with K3Li2Nb5O15, the K3Li2Ta5O15 crystal exhibits a 60 nm blueshift of the absorption edge from 376 to 316 nm, and decreases its absorption coefficient from 2.3 to 0.3 cm−1 at 400 nm. The phase-matched frequency doubling of the Ti:sapphire infrared laser for blue SHG at room temperature has been demonstrated with the KLTN bulk crystal.

Phase-matched frequency doubling in an aluminum nitride waveguide with a tunable laser source

Frequency doubling is observed in an aluminum nitride waveguide deposited by dc reactive magnetron sputtering. Phase-matching conditions are obtained by tuning the wavelength of an optical parametric oscillator pumped by a pulsed Nd:YAG laser. The maximum second harmonic generation efficiency is obtained for the TM0(ω)-TM2(2ω) conversion process and is estimated to be around 4×10−8 W−1.

Optical Preparation of Polymers for Phase-Matched Frequency Doubling

Abstract The nonlinear optical process which permits the optical preparation of centrosymmetric materials for frequency doubling is described in terms of an orientational hole-burning effect induced through non-zero E3 resonant six-wave mixing. A permanent all-optical poling is achieved by seeding preparation under backward and forward geometries in an azoaromatic acrylic copolymer. The frequency doubling second order susceptibility reaches 90 pm/V, as large as using the more classical corona poling technique. This offers a new molecular engeneering route to the control and optimization of phase-matched oriented microstructures for frequency conversion and also for electro-optic organic devices.

Blue light generation using bulk single crystals of niobium-doped KTiOPO4

We report here new solid-solution KTiOPO4 (KTP) isomorphs, namely K1−xNbxTi1−xOPO4 and K1−xTaxTi1−xOPO4, suitable for the second-harmonic generation (SHG) of blue light. Aliovalent substitution of the Ti4+-K+ pair in KTP with Nb5+ or Ta5+ increases substantially the optical birefringence (nz−ny,x) of KTP, and blueshifts the SHG cutoff wavelengths for propagation along the x and y axes. A birefringence increase of ∼70%, and a SHG cutoff wavelength as short as 892 nm have been experimentally observed in crystals of K1−xNbxTi1−xOPO4. Detailed single-crystal x-ray structure determination reveals that the Nb substitution is ordered, with Nb strongly favoring the cis-Ti(1) sites. We discuss possible correlation between this preferential substitution and the observed compositional dependence of nonlinear susceptibilities d24, and d15. Optimal solid-solution compositions for the noncritically phase-matched frequency doubling of the 1.064 and 0.946 μm lines of Nd:YAG lasers are presented, and potential applications for these new materials are outlined.

Efficient modal dispersion phase-matched frequency doubling in poled polymer waveguides

We report the design, manufacture, and characterization of poled polymer multilayer waveguides for frequency doubling. Phase matching is obtained by using modal dispersion between the zeroth-order fundamental lightwave and the first-order second-harmonic wave. By incorporating a very thin high refractive index satellite layer, the phase-match condition can be fulfilled with concomitant large overlap between the two waves, resulting in efficient doubling.

Cerenkov-type phase-matched second-harmonic generation in DCANP Langmuir-Blodgett film waveguides

We report for the first time guided-wave second-harmonic generation in nonlinear optically active Langmuir-Blodgett (LB) films. Phase-matched frequency-doubling was observed in LB films of 2-docosylamino-5-nitropyridine (DCANP) by using the Cerenkov-type configuration. The charge transfer axis of the DCANP molecules essentially lies in a plane parallel to the dipping direction. Therefore the largest nonlinear optical coefficient d 33 could be used by exciting TE modes propagating in the film. Gratings were used to couple light at λ= 1064 nm into the LB film waveguide.

4-(N,N-Dimethylamino)-3-acetamidonitrobenzene single crystals for nonlinear-optical applications

High-quality single crystals of 4-(N,N-dimethylamino)-3-acetamidonitrobenzene (DAN) were grown from dimethylsulfoxide solutions. Crystal platelets with dimensions as large as 10 mm × 5 mm × 2 mm were produced and optically characterized. An interferometric method for the measurement of refractive indices of platelike samples was developed and used for platelet surfaces parallel to one principal axis of the indicatrix. Dispersion data of the refractive indices and the birefringence were used to calculate the optical angle and the propagation directions for phase-matched frequency doubling of Nd:YAG laser radiation as well as the dependence of phase-matching angles in the x–z plane on different wavelengths. Loci of directions for type I and type II collinear phase-matched second-harmonic generation were predicted and experimentally verified. By measuring the effective nonlinear-optical susceptibilities in several phase-matched configurations we were able to evaluate all different nonlinear-optical susceptibility coefficients allowed by Kleinman’s symmetry, the highest one being d23 = (50 ± 15) pm/V with Miller’s coefficient δ23 = (0.49 ± 0.1) m2/As.

Noncritically phase-matched frequency doubling using 994 nm dye and diode laser radiation in KTiOPO4

The characteristic properties of noncritically phase-matched frequency doubling in KTiOPO4 have been investigated using ∼1 μm radiation from a Styryl-13 dye laser. Noncritically phase-matched type II second-harmonic generation was found to occur at 994.3 nm. The unusually wide angle, temperature, and wavelength tolerances observed for this nonlinear process are attractive for the design of practical blue-green laser sources. A special strained-layer InGaAs diode laser was fabricated to operate at 994 nm and generation of blue-green 497 nm radiation by noncritically phase-matched frequency doubling was demonstrated.

Frequency doubling of Nd:YAG laser by a MNA single crystal thin film on a slab-type optical glass waveguide

A single crystal thin film of 2-methyl-4-nitroaniline (MNA) for high efficiency phase-matched frequency doubling of a Nd:YAG laser (1.064 μm) was prepared. Experimental conversion efficiency for the phase-matched frequency doubling in a thin film waveguide structure was estimated at ∼0.03% at 0.6-kW input.

Common path interferometer based on second harmonic generation

A common path interferometer utilizing noncritically phase-matched frequency doubling crystals is presented. The interference pattern is directly sensitive to the wave front shape (as the Mach-Zehnder interferometer) and is in the second harmonic of the laser source. This interferometer has twice the sensitivity of a two-beam interferometer. All the optics are 100% transmitting—no beam splitters, the contrast is adjustable, and the laser intensity pattern is not affected by the interferometer. This interferometer is similar in some ways to the point diffraction interferometer, and the two are compared in this paper. A theory of operation is given, although the reference wave of the interferometer is flatter than predicted. Several possible reasons for this are examined, but no conclusion was found.

Phase-matched frequency doubling in a LiNbO 3-sapphire waveguide

An rf-sputtered thin film of LiNbO 3 on a sapphire substrate was used as a waveguide for optical frequency doubling. Employing a Nd:YAG laser and a tunable dye laser, whose output was used to pump a stimulated Raman cell, the TM ω 0→TM 2 W 2 up-conversion process was investigated in detail and the phase matched nature of this process was demonstrated. The conversion efficiency was estimated to be about 10 −3.

Optical waveguides in barium sodium niobate

The introduction of hydrogen into single crystals of barium sodium niobate, which occurs during the usual poling procedure, causes refractive-index changes that permit the propagation of optical guided waves. Propagation of TM modes can be achieved even when the boundary between the hydrogenated and unhydrogenated region of the crystal is remote from the crystal faces. For thin hydrogenated layers, both TE and TM modes can be propagated. Phase-matched frequency doubling of the cw output of a Nd–YAG laser was demonstrated in such a layer.