Showing papers on "High harmonic generation published in 1976"
TL;DR: In this article, the second harmonic generation was observed in a GaAs waveguide having a grating etched in one interface, where phase matching occurs when β2−2β1−ϑ=0, where ϑ=2π/Λ is the wave vector of the grating.
Abstract: Using a tunable laser operating near 2 μm, second harmonic generation was observed in a GaAs waveguide having a grating etched in one interface. Phase matching occurs when β2−2β1−ϑ=0, where ϑ=2π/Λ is the wave vector of the grating of period Λ and β1 and β2 are the fundamental and harmonic wave vectors.
57 citations
TL;DR: In this paper, a model for volume hologram formation in thick dichromated gelatin films is given, and the effects of saturation and dynamic absorption increase during exposure are considered in the generation of spatial harmonics.
Abstract: A model for volume hologram formation in thick dichromated gelatin films is given. Using the model and a few basic film measurements, we can quantify the index modulation vs. exposure curve. The effects of saturation and dynamic absorption increase during exposure are considered in the generation of spatial harmonics. The effects of exposure with non-unity beam-ratio and multiple incoherent exposures are predicted and experimentally verified. The thick transmission grating diffraction efficiencies resulting from first-and higher-order index modulations are calculated and compared to experiments. The methods and conclusions are applicable to other phase materials.
46 citations
TL;DR: In this article, a theoretical study of fifth-harmonic generation (FHG) in an isotropic media is presented, where two schemes are discussed: cascade generation and direct generation.
Abstract: This paper presents a theoretical study of fifth-harmonic generation (FHG) in an isotropic media. Two schemes are discussed-cascade generation in which the fifth harmonic results from successive nonlinear interactions in two separate elements, and direct generation where the fifth harmonic is produced in an isotropic media with third-and fifth-order nonlinear susceptibilities. In the plane-wave approximation almost full conversion of the pumping energy into the fifth harmonic is found to be possible. FHG with a focused Gaussian beam is also investigated. To determine the optimum conditions for FHG in the cascade scheme, the theory of four-wave mixing of light beams with arbitrary confocal parameters and waist locations is developed. In media with third- and fifth-order nonlinearity, the fifth harmonic results from step and direct processes. The interference between these two processes is discussed. Numerical calculations are presented for metal vapor-gas mixtures and Nd:glass laser pumping radiation.
40 citations
TL;DR: In this article, it was shown that the two-photon-resonant tripling of the ruby laser frequency in cesium vapor is limited by ionization, and that the laser induced Stark shift is favorable to the process in that it counteracts saturation of the resonant transition.
23 citations
Patent•
14 Jun 1976TL;DR: In this article, a nonlinear optical crystal inside the cavity of a broadband laser is used to produce frequency doubling and line-narrowing simultaneously, facilitating high power, high efficiency second harmonic generation.
Abstract: High power, high efficiency second harmonic generation is obtained by employing a nonlinear optical crystal inside the cavity of a broadband laser. The birefringent property of the crystal and the nonlinear parametric interaction produce frequency doubling and line-narrowing simultaneously, facilitating high efficiency operation.
21 citations
TL;DR: The measured third harmonic power output from a paramagnetically doped superconductor in a strong microwave field has been found to vary with temperature as (1-t)/sup -1//, as predicted by Gor'kov and Eliashberg's theory for concentrations close to critical as mentioned in this paper.
Abstract: The measured third harmonic power output from a paramagnetically doped superconductor in a strong microwave field has been found to vary with temperature as (1-t)/sup -1/, as predicted by Gor'kov and Eliashberg's theory for concentrations close to critical and Eliashberg's theory for the dilute alloy. The magnitude of the order-parameter relaxation time deduced from the measured power is consistent with a model constructed from these two theories. (AIP)
21 citations
TL;DR: In this article, an efficiency of 3% was obtained in the generation of the second harmonic of nonmonochromatic neodymium laser radiation in an LiIO3 crystal.
Abstract: An efficiency of ~3% was obtained in generation of the second harmonic of nonmonochromatic neodymium laser radiation in an LiIO3 crystal. The laser was operated under free-oscillation conditions and the dispersion of phase matching was compensated by a diffraction grating. An investigation was made of the angular and spectral characteristics of the harmonic radiation. It was found that compensation of the phase-matching dispersion widened the harmonic spectrum from 0.2–0.3 nm to half the width of the laser spectrum.
20 citations
TL;DR: In this paper, a new method for determining transition probabilities of atomic and molecular system has been demonstrated based on a measurement of the refractive index using the phase matching condition in frequency mixing or harmonic generation experiments.
12 citations
TL;DR: In this article, the transmitted and reflected second harmonic generation for a parallel-plate Fabry-Perot structure including all the effects of interference and multiple reflections is computed for a 97.5μmthick GaAs plate, obtained using a fundamental near 2μm from a wavelength-tunable parametric oscillator.
Abstract: The transmitted and reflected second harmonic generation is computed for a parallel-plate Fabry-Perot structure including all the effects of interference and multiple reflections. As a function of wavelength, the spectra consist of rapid Fabry-Perot oscillations superimposed on the more slowly varying coherence-length fringes. The harmonic generation from a 97.5-μm-thick GaAs plate, obtained using a fundamental near 2μm from a wavelength-tunable parametric oscillator, is in good agreement with the theoretical calculations.
10 citations
01 Jan 1976
TL;DR: In this article, the authors proposed a coherent anti-Stokes Raman scattering (CARS) method for nonlinear optical spectroscopy. But this new tool offers the advantage of very large optical signals, due to the parametric-like character of the sideband generation.
Abstract: Coherent anti-Stokes Raman Scattering (CARS) now ranks among the most useful phenomena in nonlinear optics A large number of applications of nonlinear optics had previously “been geared to the generation of new frequencies by harmonic generation or multiple wave mixing In CARS on the contrary, one is ultimately interested in the material which supports the optical mixing: the fluxes generated in the sidebands are merely collected and measured, so as to yield the value of the nonlinear susceptibility Since that susceptibility depends on the invariants of the Raman tensor and exhibits the same Raman vibrational, rotational and electronic resonances, one has in CARS an alternate tool for Raman spectroscopy But this new tool offers the advantage of very large optical signals, due to the parametric-like character of the sideband generation
8 citations
TL;DR: In this article, a method for finding nonzero and linearly independent higher-rank tensor elements by recourse to irreducible spherical tensors is proposed, which is applied to the analysis of free as well as electric field induced second-and third-harmonic generation of laser light.
Abstract: A method for finding nonzero and linearly independent higher-rank tensor elements by recourse to irreducible spherical tensors, is proposed. A transformation matrix from third-rank tensors, defined in circular-cylindrical coordinates, to irreducible spherical tensors, is derived. Nonzero elements of polar third- and fourth-rank tensors, symmetric in all indices, are determined for all crystallographical classes. The results are applied to the analysis of free as well as electric field- induced second- and third-harmonic generation of laser light.
TL;DR: In this article, the authors propose a nonlinear susceptibilities for atoms and molecules for device applications (e.g., harmonic generation and frequency conversion) and for spectroscopy.
TL;DR: This paper expands a distorted beam in terms of the component modes by using the experimental beamscan and calculates the second harmonic profile using this expansion, and this calculational procedure is found to be consistent with experimental observations.
Abstract: Previous measurements of electric field induced second harmonic generation indicated that the confocal parameter for a laser beam as calculated from the second harmonic intensity profile was in disagreement with that calculated from the measured beam diameter. In this paper, we show that this discrepancy is caused by the departure of the beam from the pure TEM00 mode. We expand a distorted beam in terms of the component modes by using the experimental beamscan and calculate the second harmonic profile using this expansion. This calculational procedure is found to be consistent with experimental observations.
TL;DR: In this paper, a dispersive effect on the nonlinear generation of ion-acoustic wave harmonics is reported, which is a spatial beat modulation of the second harmonic with a beating length L given by the dispersion.
Abstract: The observation of a dispersive effect on the nonlinear generation of ion‐acoustic wave harmonics is reported. This effect is a spatial beat modulation of the second harmonic with a beating length L given by the dispersion: L=2π/[K (2ω)−2K (ω)].
TL;DR: In this article, the second harmonic generation in piezoelectric semiconductors with energy-dependent relaxation times in the presence of an acoustic wave was studied and the collision term given by Sharma and Kaw was used to solve the Boltzmann equation.
Abstract: In this paper, we study the second harmonic generation in piezoelectric semiconductors with energy‐dependent relaxation times in the presence of an acoustic wave. The interaction of electrons with the acoustic wave is taken into account through piezoelectric coupling. In contrast to earlier works, we use the collision term, given by Sharma and Kaw which is valid for energy‐dependent relaxation times and use it to solve the Boltzmann equation. Our calculations show that the values of the second harmonic yield for various values of ql differ significantly for ql≪1 and are close for ql≫1 with the corresponding values obtained by using the Cohen‐Harrison‐Harrison (CHH) collision model. Further, the second harmonic yield has a maximum at ql≫1.
TL;DR: In this article, the nonlinear optical susceptibility χ231 was determined from the results of electro-optic measurements and the dispersion law was determined and it was used to find the contributions of electrons in the lattice to the non-linear refractive index.
Abstract: The nonlinear optical susceptibility χ231 was determined from the results of electro-optic measurements. Special attention was paid to possible systematic errors arising in the measurement of the induced birefringence and hindering correct interpretation of the electro-optic spectra. The dispersion law was determined and it was used to find the contributions of electrons in the lattice to the nonlinear refractive index. A comparison of the experimental conditions in second-harmonic generation and electro-optic measurements yielded a calculation formula for the nonlinear (quadratic) susceptibility χ231 of GaAs and GaP. The calculated results were in good agreement with the theory and experiments involving optical harmonic generation. The threshold of the singularity partly responsible for the nonlinear (quadratic) susceptibility was determined for gallium arsenide.
TL;DR: In this article, a theoretical analysis of the steady-state single-frequency Intraresonator generation of second optical harmonic under wave mismatch conditions was made, where at the fundamental frequency both resonator mirrors are totally reflecting but the second harmonic escapes without hindrance from the resonator.
Abstract: A theoretical analysis is made of the steady-state single-frequency Intraresonator generation of second optical harmonic under wave mismatch conditions It is assumed that at the fundamental frequency both resonator mirrors are totally reflecting but the second harmonic escapes without hindrance from the resonator The process of wave amplification in the active medium is described by a system of rate equations and the interaction of waves in the nonlinear medium by a system of reduced equations for the real and imaginary parts of the complex amplitudes It is assumed that the transverse structure of the waves is homogeneous An analytic solution of the problem is obtained near the threshold Numerical solutions are obtained for the case of strong pumping in a wide range of parameters of the problem It is shown that, in particular, the optimal harmonic generation conditions can be achieved even in the presence of a wave mismatch provided it does not exceed a certain critical value; it is also demonstrated that there is a multitude of optimal regimes The nonmonotonic nature of the dependence of the optimal length of the nonlinear crystal on the pump rate is established The results of an experimental investigation of the harmonic generation are in agreement with the theoretical predictions
TL;DR: In this paper, the 2nd-harmonic frequency of an X-band l.a.s. oscillator was used to extract power at 2.5 GHz for up to 170 W peak power with 4.8% efficiency.
Abstract: Results are presented which indicate that the upper frequency range of l.s.a. oscillators can be extended by extracting power at the 2nd-harmonic frequency. By selectively loading the 2nd-harmonic frequency of an X-band l.s.a. oscillator, up to 170 W peak power with 4.8% efficiency at 17.5 GHz has been obtained.
TL;DR: In this article, a three wave coupling mechanism has been used for harmonic generation in an unstable beam-plasma system, whose dispersion is small at low frequencies due to its finite geometry.
Abstract: Harmonic generation by a three wave coupling mechanism has been studied in an unstable beam‐plasma system, whose dispersion is small at low frequencies due to its finite geometry. This mechanism has been observed in the case of resonant coupling (nondispersive mode), and in the case of quasi‐resonant coupling (weakly dispersive mode). The experimental results give fair agreement with hydrodynamic theory.
01 Nov 1976
TL;DR: In this article, a pseudo-interdigital Rayleigh-wave transducer consisting of an ordinary grating deposited on a quartz crystal surface and a counter electrode separated from the grating by a dielectric layer is calculated, in an isotropic approximation, under small piezoelectric coupling conditions, using a numerical relaxation technique.
TL;DR: In this article, the behavior of the optical second harmonic due to crystal inhomogeneity and self-induced thermal effect has been considered for a focused laser beam, and the temperature profile created due to a fundamental laser beam along the crystal length shows an increase in temperature band width for various values of focusing parameter.
Abstract: The behaviour of optical second harmonic due to crystal inhomogeneity and self-induced thermal effect has been considered for a focused laser beam. Temperature profile created due to a fundamental laser beam along the crystal length shows an increase in temperature band width for various values of focusing parameter (). Normalized second harmonic power in inhomogeneous crystals increases up to an optimum value of focusing parameter. Utility of focusing is limited due to formation of filament in crystal for higher values of focusing parameter.