Showing papers on "High harmonic generation published in 1973"
TL;DR: In this article, the authors found that lines with frequencies 2ωo, 3ω0/2, ω 0/2 are found in the reflected light in both backward and 45° directions.
Abstract: When focusing an Nd glass laser (frequency ωo) onto a cryogenic target (D2 or H2) quite intense lines with frequencies 2ωo, 3ω0/2, ω0/2 are found in the reflected light in both backward and 45° directions. The lines at 2ω0 and 3ω0/2 are broadened on the low frequency side only. The occurrence and broadening of such lines may be related to parametric excitation of waves.
148 citations
TL;DR: In this paper, a phenomenological model containing one non-linear elastic constant has been proposed to explain the spatial variation of each observed harmonic on a LiNb03 delay line.
Abstract: Harmonic generation of acoustic surface waves has been observed experimentally in different laboratories on quartz, lithium niobate, and bismuth germanium oxide sub- strates and a phenomenological model containing one non- linear elastic constant has been proposed to explain the spatial variation of each observed harmonic on a LiNb03 delay line. In this paper we describe how the surface wave nonlinearities of different materials can be quantitatively compared. Using laser light deflection the growth with distance of the second harmonic was measured in LiNb03 and Bi12GeOzo for fun- damental frequencies of 50 and 100 MHz and of the second, third, and fourth harmonics in LiNb03 for a fundamental of 150 MHz. A one-dimensional, single-parameter model is used from which is obtained a system of coupled differential equa- tions describing the harmonic growth. This system is solved numerically as an initial value problem and a value of the single-parameter found for each material which gave good agreement between the measured data and the model pre- dictions. The parameter values found differ by an order of magnitude in the two materials, LiNb03 being the more strongly nonlinear.
34 citations
TL;DR: In this paper, it was shown that besides parametric excitation of ion-acoustic waves, another mechanism contributes at the same time to the second harmonic line generation in a laser-created plasma.
26 citations
TL;DR: In this paper, several possible sources of symmetry reduction are discussed for the second-harmonic ultrasound (5 to 10 MHz) with an estimated conversion efficiency of 20% has been observed for the soft shear mode in a cubic crystal.
Abstract: The generation of second-harmonic ultrasound (5 to 10 MHz) with an estimated conversion efficiency \ensuremath{\gtrsim} 20% has been observed for the soft shear mode in ${\mathrm{V}}_{3}$Si below 77\ifmmode^\circ\else\textdegree\fi{}K. The harmonic generation is a manifestation of the unusually large shear anharmonicity for this unstable compound; however, static symmetry arguments forbid the generation of an even-ordered harmonic for a high-symmetry shear wave in a cubic crystal. Several possible sources of symmetry reduction are discussed.
20 citations
TL;DR: In this paper, nonlinear optical constants of the alkali metals, responsible for the second harmonic generation, were calculated using the Drude model, and it was found that the electric quadrupole term of the nonlinear polarization is larger than that of a previous theory of Jha by a major factor of ω 2 p /ω 2.
17 citations
Patent•
20 Jul 1973
TL;DR: In this article, a traveling wave frequency converter based on the harmonic generation was proposed, where the phase velocities of the fundamental and harmonic frequency radiations transmitted are substantially matched with one another.
Abstract: The present invention relates to travelling wave frequency converter arrangements based on the harmonic generation. The converter in accordance with the invention comprises a harmonic generation interface obtained by bringing together a metal film and an optical waveguide layer whose thickness is such that the phase velocities of the fundamental and harmonic frequency radiations transmitted are substantially matched with one another. Optical coupling means are associated with the optical waveguide and electrical means may be provided for altering the phase velocity matching.
12 citations
TL;DR: In this paper, the dispersion roots from the cold beam type to the hot beam type were observed and it was in good agreement with the theoretical prediction by O'Neill and Malmberg.
Abstract: The spatial growing plasma wave excited by an electron beam been studied. The gradual change of the dispersion roots from the cold beam type to the hot beam type was observed and it was in good agreement with the theoretical prediction by O'Neil and Malmberg. The nonlinear saturation mechanism of the growing plasma wave was also interpreted by the change of the dispersion roots which was caused by the feedback effect of the wave on the beam particles. the harmonic spectrum near onset of the saturation did not show the power spectrum of ω -5 or ω -2.5 . The termination of the saturation level of the unstable plasma wave was observed for the case of the high beam current, but the mechanism is not clear.
11 citations
01 Jan 1973
TL;DR: The nonlinear properties of the ac Josephson effect have been demonstrated in the laboratory by a number of experiments in which the interaction of a Josephson junction with external radiation or with a resonant cavity, or with both, has been the focus of attention as mentioned in this paper.
Abstract: The non-linear properties of the ac Josephson effect(1) have been demonstrated in the laboratory by a number of experiments in which the interaction of a Josephson junction with external radiation, or with a resonant cavity, or with both, has been the focus of attention. Experiments have been reported in which Josephson junctions were employed in harmonic generation,(2)(3)(4) mixing,(5) (6)(7) generation and self-mixing,(8) and far-infrared detection.(9) (10) As a detector, there have been quoted sensitivities of 5 × 15–15 Watt,(10) speeds of better than 10 nanosecond,(9) and frequency response extending from very long wavelengths to better than 100 microns.(9) As a mixer, numbers that have been reported include conversion loss of about 6 dB at 13 GHz,(11) detection of a signal at 891 GHz by beating it against the 84th harmonic of a signal at 10.6 GHz,(6) and upconversion from 20 GHz to about 500 GHz.(8) None of these figures appears to represent a device limit. Other activity is also underway. The ac Josephson effect is the heart of a system to maintain the legal volt in terms of frequency and hence improve the reliability of standards intercomparisons around the world.(12)
8 citations
TL;DR: In this paper, the dependence of second harmonic power on crystal length, absorption, beam radius and the angle between the two fundamental waves is obtained for optical second harmonic generation when a noncollinear arrangement is employed.
8 citations
01 Jan 1973
8 citations
Patent•
20 Aug 1973TL;DR: In this paper, an almost symmetric waveguide geometry, narrow waveguide widths and the lowest order TE or TM modes are used for harmonic generation, parametric oscillation, and upconversion of radiation.
Abstract: A device for achieving optical mixing in optical waveguides which is not dependent upon a precise and uniform waveguide thickness. This result is accomplished by using an almost symmetric waveguide geometry, narrow waveguide widths and the lowest order TE or TM modes. Such systems are used for harmonic generation, parametric oscillation, and upconversion of radiation.
TL;DR: In this paper, a plane electromagnetic wave is propagated in a non-linear non-dissipative isotropic dielectric and a method is given for the calculation of the change in the amplitudes and phases of harmonics of all orders, as the wave progresses.
Abstract: A plane electromagnetic wave is propagated in a non-linear non-dissipative isotropic dielectric. A method is given for the calculation of the change in the amplitudes and phases of harmonics of all orders, as the wave progresses, for any specified dependence of the dielectric constant on the magnitude of the electric field and for any initial wave form. The calculations are valid provided the distance of travel is sufficiently small that shocks are not formed. The formulae for the amplitudes and phases of the various harmonics take a particularly simple form when the initial wave-form is sinusoidal and the non-linearity of the dielectric is not too great.
TL;DR: In this article, the power flow at the frequencies of interest in a Josephson element was investigated and general power flow relations for phase-locked and phase-unlocked Josephson elements were presented.
Abstract: A Josephson element is a nonlinear lossless element that is characterized by an internal frequency, ω 0 ;, the autonomous frequency, proportional to the dc voltage across the element. Detection, mixing, generation, harmonic generation and mixing, and parametric amplification are possible using such an element. We present here general relations for the power flow at the frequencies of interest in such an element. These general power flow relations depend upon whether the autonomous frequency is phase-locked, either harmonically or subharmonically, to a frequency in the system or is unlocked. The results here generalize those given previously by Russer for the harmonically locked case.
TL;DR: The Kerr effect is used as a means of phase matching in the isotropic medium to consider two interacting laser beams in an active nonlinear medium.
Abstract: For potential applications in scanning and measurement, we consider two interacting laser beams in an active nonlinear medium. The nonlinear medium generates two new beams at the same frequency and in directions different from the incident beams. The Kerr effect is used as a means of phase matching in the isotropic medium.
TL;DR: In this paper, the authors investigated the harmonic generation of an incident extraordinary wave at the upper hybrid and cyclotron frequency in a homogeneous plasma located in a uniform magnetic field, where the incident microwave propagated along the density gradient in the direction of decreasing magnetic field such that the harmonic emission was spatially localized.
Abstract: Harmonic generation of an incident extraordinary wave at the upper hybrid and cyclotron frequency in a homogeneous plasma located in a uniform magnetic field was investigated. In the experimental configuration the incident microwave propagated along the density gradient in the direction of decreasing magnetic field such that the harmonic emission was spatially localised.
TL;DR: In this paper, an analysis by transport theory has been performed for microwave 2nd-harmonic generation using the nonlinearity of negative resistance in n-type GaAs under a small-signal excitation.
Abstract: An analysis by transport theory has been performed for microwave 2nd-harmonic generation using the non-linearity of negative resistance in n-type GaAs under a small-signal excitation. As a result of this analysis, the detailed frequency responses which are affected by the various scattering relaxation times of carriers become clear. Moreover, it is suggested that this multiplying method would be able to operate with very high conversion efficiency, in contrast to the customary large-3ignal operation.
01 Jan 1973
TL;DR: In this article, Deen et al. considered double-electrode transducers having equal responses at the 7st and 3rd harmonic with h,/8 wide fingers, or at the 1st 3rd, 5th and 7th harmonic with&/16 wide fingers.
Abstract: Surface-wave filters having bandwidths of less than 1 per cent have been investigatedon Y-2 lithium niobate ST and YX quartz at 30 MHz Filters with Q's up to 600 have been constructed on quartz showing good undis- torted passband characteristics Our empnasis nas Deen on harmonic generation of surface waves and the advantages it offers, such as larger finger dimensions and higher manufacturing yield We have considered double-electrode transducers having equal responses at the 7st and 3rd harmonic with h,/8 wide fingers, or at the 1st 3rd, 5th and 7th harmonic with&/16 wide fingers, A, 1st harmonic frequency Filters on YZ lithium niobate show stronger background bulk noise radiation and passband distortion than ST and YX quartz A zero temperature coefficient is for most applications more important than a low in- sertion loss, such that 3rd and 7th harmonic operation on ST quartz seem to be the optimum choice for narrow-band filters having Q's in excess of 1000 being the
TL;DR: In this paper, the cross sections for second harmonic generation of surface acoustic waves have been calculated from the rigorous theory of thermoelasticity, where the nonlinear wave equation is satisfied by mechanical displacements which also maintain the boundary stress free at the harmonic frequency.
Abstract: The cross sections for second harmonic generation of surface acoustic waves have been calculated from the rigorous theory of thermoelasticity. In this treatment, the nonlinear wave equation is satisfied by mechanical displacements which also maintain the boundary stress free at the harmonic frequency. Calculations for various cuts on α‐quartz and sapphire are presented.
TL;DR: In this paper, the second harmonics of sound waves propagating in uniaxially stressed cubic crystals were discussed on the basis of the nonlinear thermoelasticity theory.
Abstract: The generation of the second harmonics of sound waves propagating in uniaxially stressed cubic crystals was discussed on the basis of the nonlinear thermoelasticity theory. The direction of the applied stress was chosen as , , or , and the pure-mode wave propagation along the directions perpendicular of parallel to the stresses was considered. The stress derivative of the amplitude of the harmonic wave was expressed as a function of the second-, the third-, and the fourth-order elastic constants. Eight cases with different stress directions and wave characters were found to be independent. It was shown that, together with four cases in the hydrostatically stressed crystals, all eleven fourth-order elastic constants could be determined through the harmonic generation experiments.
01 Nov 1973
TL;DR: In this paper, the authors provide a theoretical study of the ability of single-valued characteristics to generate linear harmonics and show that piecewise linear characteristics cannot generate linearly odd components.
Abstract: A linear-harmonic generator is a nonlinear device in which an applied cosine wave of amplitude A causes some harmonic(s) of the input to be generated with amplitude(s) proportional to A. Such devices find application in phase-envelope processing in some types of modulation and speech-transmission systems. The present paper provides a theoretical study of the ability some characteristics have to generate linear harmonics. Linear-harmonic generation by single-valued characteristics which are representable by piecewise linearisation and those representable by a power series are investigated. It is shown that piecewise linear characteristics cannot generate linearly odd components. Also, it is shown that a characteristic expanded by a power series cannot generate linear harmonics, for either even or odd components. A particular single-valued characteristic, which precisely generates odd-harmonic components, is found, although it cannot be practically realised without approximation.
TL;DR: In this paper, a step recovery diode (SRD) is used for harmonic generation and pulse forming a fast rising waveform rich in harmonics is provided by using epitaxial mesa structure.
Abstract: For harmonic generation and pulse forming a fast rising waveform rich in harmonics is needed. This characteristic is provided by a step recovery diode (SRD).This paper presents design theory and fabrication steps for the SRD using epitaxial mesa structure. The diodes fabricated show breakdown voltages in the range of 60–80 volts with a ‘punch-through’ at 5 volts. The storage time and transition time of the diodes are 20 and 5 ns respectively. The ‘pill-with-prongs’ type case has been used for housing the diodes.