Showing papers on "High harmonic generation published in 1991"
TL;DR: A detailed analysis of a subharmonically seeded single-pass free-electron laser utilizing two wiggler magnets separated by a dispersion section and the physical process in the system and the optimization of parameters is presented.
Abstract: We present a detailed analysis of a subharmonically seeded single-pass free-electron laser (FEL) utilizing two wiggler magnets separated by a dispersion section. To be specific, suppose the seed to be laser light at 300 nm. A first wiggler is used to energy modulate the electron beam. This is followed by a dispersion section to produce spatial bunching, and a second wiggler resonant to 100 nm. Upon passing through the second wiggler, the prebunched electron beam first radiates coherently, and then this radiation is exponentially amplified. Finally, a tapered section is used to extract additional power from the electron beam. In this manner we can achieve pulses of duration {approx}10 psec with 1 mJ per pulse in 10{sup {minus}4} bandwidth, with continuously tunable wavelength in the range 100--300 nm. We present the analytical tools we have employed for the preliminary estimate of the system performance and of the optimization of the parameters. We describe our modification of the simulation code TDA to include harmonic generation and discuss its use in analyzing the subharmonically seeded FEL. The analytic and computer-simulation calculations are in good agreement. We discuss in detail the physical process in the system and the optimization of parameters.
472 citations
TL;DR: In this paper, the authors present theoretical studies of high-order harmonic generation in a rare-gas medium using a 1064 nm Nd-YAG laser in the 1013 W cm-2 intensity range.
Abstract: The authors present theoretical studies of high-order harmonic generation in a rare-gas medium. The experimental results obtained at Saclay with a 1064 nm Nd-YAG laser in the 1013 W cm-2 intensity range are summarized. The harmonic emission strengths, first decrease rather steeply for the first orders, then form a long plateau up to the 21st harmonic in xenon, or up to the 33rd harmonic in argon, before decreasing again rather abruptly. The theoretical description of these experiments consists first in the calculation of the photoemission spectra emitted by a single atom. The spectra are obtained by numerically integrating a time dependent Schrodinger equation for the laser-excited rare-gas atom. Second, one must account for collective effects in the medium, described by Maxwell's equations. A theoretical framework for describing the generation and propagation of harmonics in strong laser fields is developed. An numerical solution of the propagation equations for the harmonic fields in xenon at 1064 nm provides results which agree well with experimental data.
282 citations
TL;DR: In this paper, the authors demonstrated a new method of generating pulses of freely propagating THz electromagnetic radiation, which are the shortest directly measured THz pulses in free space to date and are more powerful than those generated by Hertzian dipoles or by resonant dipole antennas.
Abstract: We have demonstrated a new method of generating pulses of freely propagating THz electromagnetic radiation. The resulting 380 fs pulses are the shortest directly measured THz pulses in free space to date and are more powerful than those generated by Hertzian dipoles or by resonant dipole antennas. Temporal features as short as 190 fs were observed on these THz radiation pulses and thereby, illustrate an ultrafast receiver response time.
218 citations
TL;DR: The weaker variation with pump intensity of the induced dipole in the high-field regime leads to an enormous enhancement in phase matching compared to the perturbative limit and a defocusing of the generated harmonics.
Abstract: We present a completely ab initio calculation of harmonic generation in xenon exposed to a strong laser field. The time-dependent Schrodinger equation for the atomic response and the propagation equation are numerically integrated yielding excellent agreement with experiment. The weaker variation with pump intensity of the induced dipole in the high-field regime leads to an enormous enhancement in phase matching compared to the perturbative limit and a defocusing of the generated harmonics.
120 citations
TL;DR: In this paper, the authors present a new set of refractive index values with better than fourth decimal place precision, as well as measurements of the thermo-optic parameters.
Abstract: 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. >
117 citations
TL;DR: In this paper, a visible, surface-emitting, solid-state diode laser for InGaAs, InP, and GaAs geometries, as well as for several other devices, is described and demonstrated.
Abstract: Proof-of-concept devices to create surface-emitting visible lasers are described and demonstrated. A visible, surface-emitting, solid-state diode laser for InGaAs, InP, and GaAs geometries, as well as for several other devices, is discussed. The use of a multilayer system to enhance the waveguide harmonic mixing over a large bandwidth is demonstrated. The resulting surface-emitted light can then be used to measure frequency differences of multiple optical channels in a fiber communication system. It can also be used for nonblocking switching systems. Since phase is preserved by the harmonic mixing, the device is also usable in coherent communication schemes. Experimental measurements of harmonic generation coefficients for a large Al alloy content in AlGaAs are presented. >
76 citations
TL;DR: Stimulated backscattered harmonic radiation generated by the interaction of an intense pump-laser field with an electron beam or plasma is analyzed using a fully nonlinear, relativistic, fluid theory valid to all orders in the pump- laser amplitude.
Abstract: Stimulated backscattered harmonic radiation generated by the interaction of an intense pump-laser field with an electron beam or plasma is analyzed using a fully nonlinear, relativistic, fluid theory valid to all orders in the pump-laser amplitude. The backscattered radiation occurs at odd harmonics of the Doppler-shifted incident laser frequency. The growth rates, saturation levels (efficiencies), and thermal limitations are calculated for the backscattered harmonic radiation. This mechanism may provide a practical method for producing coherent radiation in the XUV regime.
65 citations
TL;DR: Efficient frequency conversion of cw mode-locked Ti:A1(2)O(3) laser radiation using lithium triborate, beta-barium borate, and lithium iodate crystals as the nonlinear material is demonstrated.
Abstract: Efficient frequency conversion of cw mode-locked Ti:Al2O3 laser radiation using lithium triborate, β-barium borate, and lithium iodate crystals as the nonlinear material is demonstrated. Second-, third-, and fourth-harmonic generation results in tunable blue and ultraviolet radiation down to 205 nm with transform-limited pulses and pulse lengths below 1 ps. Maximum average powers (repetition rate 82 MHz) of 700 mW at 400 nm, 120 mW at 272 nm, and 10 mW at 210 nm were obtained. The effects of group-velocity dispersion have to be taken into account to optimize the different frequency-conversion processes.
65 citations
TL;DR: In this article, a second-harmonic generation in the 26-40 GHz band through soliton propagation on a GaAs monolithic nonlinear transmission line was reported, at 20-dBm input power, a 20-diode structure attained >
Abstract: A second-harmonic generation is reported in the 26-40-GHz band through soliton propagation on a GaAs monolithic nonlinear transmission line. At 20-dBm input power, a 20-diode structure attained >
55 citations
IBM1
TL;DR: In this paper, the authors extended the optical transfer matrix technique for the analysis of optical harmonic generation and mixing in laminar structures to include the case of anisotropic media, where attenuation and phase shifts of the pump beams due to nonlinear interactions can be neglected.
Abstract: The optical transfer matrix technique for the analysis of optical harmonic generation and mixing in laminar structures is extended to include the case of anisotropic media. This approach is applicable in the limit of low conversion efficiencies, where attenuation and phase shifts of the pump beams due to nonlinear interactions can be neglected. In this approximation one first solves the linear problem for the pump waves in the structure, using optical transfer matrices to take all reflections and linear attenuation into account. Then the nonlinear polarizations driven by these waves are found, and finally expressions for the waves at the harmonic and combination frequencies generated by these polarizations are derived, again using transfer matrices to account exactly for all reflections and linear attenuation. In the anisotropic case 4 × 4 transfer and propagation matrices are required, and all polarization components are treated simultaneously. The results are given in a computationally convenient form.
47 citations
TL;DR: In this paper, a multiple quantum well GaAs/AlGaAs laser with two electrically isolated contacts is passively mode locked in an external cavity at the first through sixth harmonics of the pulse roundtrip frequency of 1.17 GHz to produce pulses shorter than 10 ps.
Abstract: A multiple quantum well GaAs/AlGaAs laser with two electrically isolated contacts is passively mode locked in an external cavity at the first through sixth harmonics of the pulse round‐trip frequency of 1.17 GHz to produce pulses shorter than 10 ps. The repetition rate is switched between harmonics by adjusting the gain section current, and large hysteresis between the different repetition rates is observed, with up to four different repetition rates for the same gain current. The results are compared with small and large signal passive mode‐locking theories by considering modifications to the saturated gain recovery between pulses when the laser operates at different harmonics.
TL;DR: In this article, the authors proposed a simple theoretical model to explain the third-harmonic generation process, which arises from the scattering of electrons by ions in the presence of the strong laser field.
Abstract: Relatively efficient (up to 3%) third-harmonic generation of picosecond Nd:YAG laser pulses for wavelength λ = 1.06 μm in a low-density laser plasma is reported for a coherent (i.e., collinear) geometry. The third-harmonic beam produced is nearly diffraction limited and coherent and can be used in other nonlinear-optical experiments. A simple theoretical model is proposed in order to explain this result. In the model, third-harmonic generation is considered to be a process that arises from the scattering of electrons by ions in the presence of the strong laser field.
Patent•
09 Oct 1991
TL;DR: In this article, a high-order harmonic laser was proposed, which consists of a output coupler, total reflection mirror, and a laser medium disposed there between. But the output couplers and the total reflection mirrors form a resonator.
Abstract: An intra-cavity high order harmonic laser consists of a output coupler, total reflection mirror, and a laser medium disposed therebetween. The output coupler and the total reflection mirror form a resonator. At least two nonlinear crystals are disposed between the laser medium and the output coupler. One of the crystals acts as a frequency doubler, doubling the fundamental frequency of the laser and the other crystal acts as a frequency mixer or high order harmonic doubler in order to produce higher nth order harmonic (n≧2). The invention overcomes the disadvantages associated with producing a high order harmonic laser beam in low peak power lasers such as CW lasers.
01 Jul 1991-Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment
TL;DR: In this article, the nonlinear properties of the free electron laser gain that result when an electron beam is bunched by an external pulsed laser have been explored for the purpose of producing coherent light in the VUV spectral range.
Abstract: The goal of this experiment is to explore the possibility of producing coherent light in the VUV spectral range using the nonlinear properties of the free electron laser gain that result when an electron beam is bunched by an external pulsed laser. The positive results, that have been obtained in 1987 on the old storage ring ACO, have lead us to install an experiment on Super-ACO, but with some modifications. This article presents the most recent results obtained on Super-ACO, where coherent photons have been produced at the 3rd (177 nm) and 5th (106 nm) harmonics of the incident laser. It presents also a brief summary of the practical interest and difficulties of this techniques.
TL;DR: In this paper, a new nonlinear crystal thienylchalcone (T‐17) was grown from acetone by the falling temperature method and the nonlinear optic properties were determined.
Abstract: Large single crystals (60×20×8 mm3) of a new nonlinear crystal thienylchalcone (T‐17) were grown from acetone by the falling temperature method and the nonlinear optic properties were determined. The effective nonlinear optical coefficient, the angular acceptance (Δθ,Δφ), and the walk‐off angle were 7.1 pm/V, 0.053° cm, 1.2° cm1/2, and 3.6°, respectively. Thienylchalcone could be type‐I phase matched for the light of wavelengths longer than 910 nm. It is an attractive nonlinear crystal for generating green and blue lasers.
TL;DR: A Fourier analysis of the Rayleigh-Plesset equation is used to obtain an approximate solution for the nonlinear effects in the oscillation of a single bubble in an infinite fluid, and the resulting expressions are evaluated numerically in order to examine the non linear effects.
Abstract: This paper persents a spectral analysis of the response of a fluid containing bubbles to the motions of a wall oscillating normal to itself. First, a Fourier analysis of the Rayleigh-Plesset equations is used to obtain an approximate solution for the nonlinear effects in the oscillation of a single bubble in an infinite fluid. This is used in the approximate solution of the oscillating wall problem, and the resulting expressions are evaluated numerically in order to examine the nonlinear effects. Harmonic generation results from the nonlinearity. It is observed that the bubble natural frequency remains the dominant natural frequency in the volume oscillations of the bubbles near the wall. On the other hand, the pressure perturbations near the wall are dominated by the first and second harmonics present at twice the natural frequency while the pressure perturbation at the natural frequency of the bubble is inhibited. The response at the forcing frequency and its harmonics is explored along with the variation with amplitude of wall oscillation, void fraction, and viscous and surface tension effects. Splitting and cancellation of frequencies of maximum and minimum response due to enhanced nonlinear effects are also observed.
TL;DR: In this article, the potential of lithium triborate (LBO) temperature-tuned to achieve type-I noncritical phase matching, for picosecond high-power second-harmonic generation (SHG) and tunable optical parametric amplification (OPA), was evaluated.
Abstract: We evaluate the potential of lithium triborate (LBO) temperature‐tuned to achieve type‐I noncritical phase matching, for picosecond high‐power second‐harmonic generation (SHG) and tunable optical parametric amplification (OPA). Pumped by 35 ps, 1.064 μm laser pulses, a conversion efficiency of 65% was obtained from SHG. The output of OPA, pumped by 0.532 μm was tunable from 0.75 to 1.8 μm with an efficiency better than 20%.
Patent•
07 Jan 1991TL;DR: In this paper, a micro-laser is formed from a substantially thin etalon of a self-doubling crystal which has two opposite faces and which is positioned relative to a close coupled and diode pumped source of optical radiation, for resonantly enhanced phase-matched harmonic generation along an axis of propagation which is substantially perpendicular to the two faces of the etalon.
Abstract: A micro-laser is formed from a substantially thin etalon of a self-doubling crystal which has two opposite faces and which is positioned, relative to a close coupled and diode pumped source of optical radiation, for resonantly enhanced phase-matched harmonic generation along an axis of propagation which is substantially perpendicular to the two faces of the etalon.
TL;DR: In this paper, the authors compare calculated optical harmonic spectra for the hydrogen molecule and the hydrogen atom in an intense, linearly polarized laser field, and show that if the H 2 bond length is stretched so that H 2 has the same ionization potential as H 2, both systems produce remarkably similar spectra when irradiated with a 1064 nm laser at 1 × 10 14 or 2 × 10 13 W/cm 2.
TL;DR: In this article, the effect of nonuniformity in graded index, channel waveguide dimensions on the phase matching condition for guided-wave nonlinear frequency conversion was studied, and theoretical and experimental results using normalized waveguide parameters and quasi-phase matching for second- harmonic generation in annealed proton-exchanged LiNbO3 waveguides were provided.
Abstract: We have studied the effect of nonuniformity in graded index, channel waveguide dimensions on the phase‐matching condition for guided‐wave nonlinear frequency conversion. Both theoretical and experimental results using normalized waveguide parameters and quasi‐phase matching for second‐ harmonic generation in annealed proton‐exchanged LiNbO3 waveguides show the existence of an optimum waveguide design which is insensitive to inhomogeneities in the waveguide dimensions. Application of such a waveguide design using normalized approach can significantly relax the fabrication tolerance, leading to nonlinear guided‐wave devices with long interaction lengths and useful conversion efficiencies.
Book•
01 Jan 1991
TL;DR: In this paper, the theory of MSB free-free and bound-free field-induced coherent transitions in a single atom above-threshold ionization has been studied in a semi-classical approach.
Abstract: Stimulated Bremsstrahlung multiphoton stimulated Bremsstrahlung spontaneous and stimulated compton scattering ponderomotive potential, Kapitza-Dirac effect and transverse electron channeling in a standing wave free electron lasers laser acceleration of electrons wave packets and their free evolution wave packets in the theory of MSB free-free and bound-free field-induced coherent transitions in a single atom above-threshold ionization - perturbation theory and semi-classical approach, method of essential states, AC Stark shift and ponderomotive acceleration, ATI in the limit of extremely short pulses, harmonic generation interference suppression of photoionization from Rydberg levels in a strong ionizing field
TL;DR: In this article, the second order nonlinear optical properties of doped polymer thin films are studied by optical second harmonic generation and electro-optic coefficient measurements, and the results show that cross-linked polymers are more stable, whereas orientation in guest-host systems decay rapidly with time.
Abstract: Second order nonlinear optical properties of doped polymer thin films are studied by optical second harmonic generation and electro-optic coefficient measurements. The studied thin films are guest-host systems and cross linked polymers with charge transfer noncentrosymmetric amines as curing agents. The in situ second harmonic generation (SHG) measurements during poling optimize the poling process and give corresponding components of (chi) (2)(- 2(omega) ;(omega) ,(omega) ) tensor depending on the fundamental harmonic electric field polarization configurations. At the same time they follow the stability of induced dipolar orientation by poling. Obviously, crosslinked polymers are more stable, whereas orientation in guest-host systems decay rapidly with time. The electro-optic measurements in thin films by reflection using the technique proposed by Teng and Man and by Schildkraut measures r33 coefficient even in the doped polymer absorption band and give its real and imaginary parts.
Journal Article•
TL;DR: In this article, an efficient internally frequency-doubled mode-locked Nd:YAG laser has been operated, which makes use of an intracavity harmonic mirror to produce 1.5 W of 0.53μ power in the output beam.
Abstract: An efficient internally frequency‐doubled mode‐locked Nd:YAG laser has been operated. An interaction between the intracavity harmonic generation and mode locking, which results in a lengthening of the mode‐locked pulse and a corresponding decrease in fundamental circulating power, has been observed with this laser. The laser makes use of an intracavity harmonic mirror to produce 1.5 W of 0.53‐μ power in the output beam. A significant decrease in laser noise is observed when the laser is mode locked.
TL;DR: Developpement d'une technique des interferences optiques non lineaires dans la generation des harmoniques secondaires de surface, pour mesurer directement la variation de the susceptibilite non lineaire of the surface de CO/Ni(110) en fonction du recouvrement en CO.
Abstract: A nonlinear-optical-interference technique in surface second-harmonic generation is developed to measure directly the variation of surface nonlinear susceptibility of CO/Ni(110) as a function of the CO coverage. It is found that some of the susceptibility elements vary linearly with the coverage and others nonlinearly. A simple model suggests that the former are dominated by contributions from nearly free electrons, while the latter by contributions from the more localized electrons.
TL;DR: Laser spiking in a long pulse Nd:YAG laser has been substantially suppressed by intracavity second harmonic generation with very little loss of laser pulse energy.
Abstract: Laser spiking in a long pulse Nd:YAG laser has been substantially suppressed by intracavity second harmonic generation with very little loss of laser pulse energy.
TL;DR: In this article, the authors review the development of FIR nonlinear spectroscopy which took place essentially in the past decade and give examples on the one hand of harmonic generation which leads to evaluate nonlinear potentials of lattice ions and mobile carriers, and on the other hand describes laser-induced population changes in electronic states which result in both saturated absorption and saturated photoconductance.
TL;DR: In this paper, a wide range of nonlinear optical coefficients and various systems of notation have been used to describe optical second-harmonic generation (SHG), and the techniques of optical nonlinear coefficient measurement and the elementary theory of SHG are briefly reviewed.
Abstract: A wide range of nonlinear optical coefficients and various systems of notation have been used to describe optical second-harmonic generation (SHG). To avoid possible confusion, the techniques of optical nonlinear coefficient measurement and the elementary theory of SHG are briefly reviewed. Absolute and relative nonlinear coefficient measurements by phase-matched SHG are described. The following results were obtained: d36(KDP) equals 0.38 pm/V, d36(KD*P) equals 0.37 pm/V, d22(BaB2O4) equals 2.2 pm/V, d31(LiIO3) equals -4.1 pm/V, d31(5%MgO:LiNbO3) equals -4.7 pm/V, d15(KTP) equals 1.9 pm/V and d24(KTP) equals 3.5 pm/V. The accuracy of these measurements is estimated to be better than 10%. An example of high-repetition-rate pulsed SHG in AgGaSe2 is given to demonstrate the use of quantitative analysis of harmonic generation for evaluation of nonlinear optical material performance.
TL;DR: In this paper, the thermal behavior of the second-harmonic generation (SHG) phase-matching loci of deuterated l-arginine phosphate (dLAP) at a fundamental wavelength of 1.064 μm was investigated.
Abstract: We present measurements of the thermal behavior of the second-harmonic generation (SHG) phase-matching loci of deuterated l-arginine phosphate (dLAP) at a fundamental wavelength of 1.064 μm. These results clearly indicate the existence of temperature-insensitive phase-matching directions that possess large nonlinear couplings. To the best of our knowledge, this property of temperature-insensitive SHG phase-matching directions is uniqe to dLAP. Such behavior can greatly decrease thermal contributions to phase mismatch in high-average-power harmonic conversion.
TL;DR: In this paper, side emitted 3ω/2 radiation was studied by interacting 1.064 μm laser light with plasmas obtained from exploding thin foils, and the observed spectral features, including substantial lack of a ''blue» component, the amount of red shift and bandwidth, are consistent with the Karttunen theory of half-integer harmonics generated in plasmons.
Abstract: Side emitted 3ω/2 radiation was studied by interacting 1.064 μm laser light with plasmas obtained from exploding thin foils. Both focusing (f/8) and collecting (f/7) optics were designed in order to reduce the instrumental bandwidth of the 3ω/2 spectrum. Time-resolved spectra and time-resolved images were obtained and analysed. All the observed spectral features, including the substantial lack of a «blue» component, the amount of red shift and bandwidth, are consistent with the Karttunen theory of half-integer harmonics generated in plasmas. This theory takes into account the propagation of ω/2 plasmons produced by «two plasmon decay» and their coupling with laser light.
TL;DR: In this paper, a 30 degrees cut frequency-doubling LiIO/sub 3/ crystal was used to mode lock both transitions, demonstrating the superiority of this mode-locking technique over that using saturable absorbers.
Abstract: Passive mode locking of a Nd:YAlO/sub 3/ laser at 1.08 and 1.34 mu m using a nonlinear mirror based on second harmonic generation is described. A single 30 degrees cut frequency-doubling LiIO/sub 3/ crystal was used to mode lock both transitions, demonstrating the superiority of this mode-locking technique over that using saturable absorbers. Pulses as short as 50 ps at 1.08 mu m and 15 ps at 1.34 mu m were obtained. A comparative analysis of the mode-locking performance at the two fundamental wavelengths is presented, indicating that the longer pulse duration at 1.08 mu m is due to the higher gain and an insufficient number of round-trips in the pulse train development. >