Nonlinear Optical Crystals: A Complete Survey

Since its discovery1, early in 1928, the scattering of light with altered frequency has been investigated in many crystals, and much valuable information has been accumulated. The significance of the results and their relation to theories of solid state are clearly matters of great interest.

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Scattering of light in crystals

Background We have previously reported that inhaled heparin prevents allergic bronchoconstriction in sheep and inhibits the anti-IgE-mediated release of histamine from mast cells in vitro. Since the release of such mediators has been implicated in exercise-induced asthma, we investigated whether inhaled heparin could also attenuate the bronchoconstrictor response in this disease. Methods On five days we studied 12 subjects with a history of exercise-induced asthma. On day 1 they underwent a standardized exercise challenge on a treadmill to document the presence of exercise-induced asthma. Minute ventilation was estimated with a calibrated respiratory inductive plethysmograph. The workload was increased until the heart rate reached 85 percent of the predicted maximal value, and was sustained for 10 minutes. The magnitude of bronchoconstriction was assessed by measuring specific airway conductance before and after the exercise. On day 2 the partial-thromboplastin time was measured in plasma obtained before ...

https://www.nejm.org/doi/pdf/10.1056/NEJM199307083290204

Preventing Bronchoconstriction in Exercise-Induced Asthma with Inhaled Heparin

We present a theory of ultrashort-pulse second-harmonic generation (SHG) in materials with longitudinally nonuniform quasi-phase-matching (QPM) gratings. We derive an expression for the output second-harmonic field generated in an arbitrary QPM grating from an arbitrary fundamental field, valid for arbitrary material dispersion in the undepleted-pump approximation. In the case when group-velocity dispersion can be neglected, a simple transfer-function relationship describes the SHG process. This SHG transfer function depends only on material properties and on the QPM grating design. We use this SHG transfer function to show that nonuniform QPM gratings can be designed to generate nearly arbitrarily shaped second-harmonic output pulses. We analyze in detail a technologically important example of pulse shaping: the generation of compressed second-harmonic pulses from linearly chirped fundamental input pulses. The efficiency of these interactions as well as the limits imposed by higher-order material dispersion are discussed.

Ultrashort-pulse second-harmonic generation with longitudinally nonuniform quasi-phase-matching gratings: pulse compression and shaping

The optical biaxial nature of crystals in the potassium titanyl phosphate (KTP) family result in anisotropic transmission that depends on the polarization direction of the transmitted radiation with respect to the fundamental crystal axes. Knowledge of the polarization-dependent crystal transmission is important for all wavelength-conversion applications and in particular is the only limitation on possible combinations of wavelengths when one uses the quasi-phase-matching techniques recently developed for the KTP family materials. In this study, polarized transmission spectra of KTiOPO4 (KTP), RbTiOPO4, RbTiOAsO4 (RTA), and KTiOAsO4 were measured over the 0.3–6-µm wavelength range with a spectrophotometer and a Fourier-transform infrared spectrometer. Seven crystal samples were studied, including four samples of KTP crystals of different origins. Variations in spectral transmission on the short- and long-wavelength edges, as well as visible-wavelength transmission and OH- absorption properties, are presented and discussed. The transmission of one sample of KTP and of RTA was also measured before and after periodic electric field poling.

Transmission measurements in KTP and isomorphic compounds

Recently, it has been demonstrated that semiorganic materials have potential for very efficient nonlinear optical devices. Among many recently reported materials is zinc tris thiourea sulfate. We report measurements of the electro‐optic, piezoelectric, and dielectric constants of this new material.

Electro‐optic, piezoelectric, and dielectric properties of zinc tris thiourea sulfate

KTA is a crystallographic isomorph of KTP that shows promise for nonlinear frequency generation throughout the 1–5-μm region. We present updated Sellmeier coefficients for KTA based on measurements of the refractive index in the 0.4–3.6-μm region. Predictions of phase-matching behavior by means of these coefficients agree well with experimental data.

Infrared corrected Sellmeier coefficients for potassium titanyl arsenate

Rubidium titanyl arsenate (RTA), a crystallographic isomorph of potassium titanyl phosphate, shows promise for nonlinear-frequency generation throughout the 1–5-µm spectral region. Difference-frequency generation in an RTA crystal produced tunable output in the 3.2–4.2-µm wavelength range. A single 1.064-µm Nd:YAG laser pumped both a LiNbO3 optical parametric oscillator used to generate a tunable signal beam and the RTA crystal used for difference-frequency generation. Conversion efficiencies were limited to 4% primarily by the large beam divergence of the signal beam. Phase-matching measurements were in excellent agreement with new IR-corrected RTA Sellmeier equations based on refractive-index measurements.

Rubidium titanyl arsenate difference-frequency generation and validation of new Sellmeier coefficients

The nonlinear phenomenon of polarization rotation in Ti:LiNbO3 optical channel waveguides was investigated using Raman microprobe microscopy. Polarization sensitive Raman selection rules permitted the identification of polarization rotation of the propagating transverse electric or transverse magnetic waveguide mode. From an analysis of the Raman scattered light collected orthogonal to the waveguide surface the threshold power necessary to initiate the process of mode conversion could be determined. In addition, the Raman microprobe was used to determine waveguide loss coefficients by collecting inelastically scattered light. The values obtained by this method were compared to those measured by collecting the elastically scattered light. A value for the asymmetric component, β15, of the photovoltaic tensor was calculated to be 7.8×10−13 A/W for the X‐cut, Y‐propagating and 3.8×10−14 A/W and 1.2×10−14 A/W for the rapid thermally annealed Z‐cut, Y‐propagating channel waveguides, respectively.

Raman investigation of the nonlinear optical phenomenon of polarization rotation in Ti:LiNbO3 channel waveguides

We report measurements of the optical properties of deuterated zinc tris thiourea sulfate (d‐ZTS). The material is being studied for its potential value in optical frequency conversion and electro‐optic applications. The electro‐optic and piezoelectric measurements along with those for the dielectric constant indicate that the figure of merit for electro‐optic modulation is comparable to that of KDP. However, careful refractive index measurements along with an analysis of the nonlinear coefficient tensor show that d‐ZTS will not noncritically phase match for second‐harmonic generation despite the promise shown by its undeuterated analog. In addition, the acceptance angle even for critical phase matching is very small.

Uma Ramabadran

Papers

Electro‐optic, piezoelectric, and dielectric properties of zinc tris thiourea sulfate

Infrared corrected Sellmeier coefficients for potassium titanyl arsenate

Rubidium titanyl arsenate difference-frequency generation and validation of new Sellmeier coefficients

Raman investigation of the nonlinear optical phenomenon of polarization rotation in Ti:LiNbO3 channel waveguides

Optical properties of deuterated zinc tris thiourea sulphate