Second—Harmonic Generation of Bessel Beams in Lossy Media

We present a further analysis for the second-harmonic generation of Bessel beams in lossy media.The emphasis is put on the effect of absorption to the radial pattern of the second-harmonic beam.It is shown that within the absorption length of the second harmonic,the Bessel second-harmonic beam approaches limited diffraction in the radial direction and behaves as in the case of lossless media.     

Photoinduced Second Harmonic Generation of CuI Microcrystalite Doped Glass

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Enhancement of Available Conversion Efficiency of Optical Parametric Amplifier in a Cascaded Photonic Crystal Structure

Using the cascaded structure of a linear and a second-order nonlinear photonic crystals, we realize a high-efficiency optical parametric amplifier in the case of exact phase matching. This proposal is verified using the slow-envelope nonlinear finite difference time domain numerical method. Compared with the case of the individual nonlinear photonic crystal structure, the oscillation threshold is decreased obviously; and the peak power amplification factor of the transmitted signal is enhanced more than 20 times.     

Second Harmonic Generation from Co Magnetic Thin Films

The magnetization-induced second harmonic generation (MSHG) in the sputtered and epitaxial-grown Co thin films was studied. The magnetic contrast of the MSHG intensity could be clearly distinguished for the cobalt films prepared by both the methods, but the signal measured in air for sputtered films was not smoother than that for the in-situ measurement of epitaxial films. Compared with the magneto-optical Kerr effect, the MSHG shows some new behaviour indicating that more information could be obtained if these two methods are combined. The MSHG reveals a giant nonlinear Kerr rotation in orders of magnitude larger than its linear one.     

Enhancement of Bichromatic High-Order Harmonic Generation by a Strong Laser Field and Its Third Harmonic

We investigate high-order harmonic generation （HHG） in a linearly polarized bichromatic field composed of a fundamental laser field with frequency w and an additional laser field with frequency 3w. The numerical results show that it is possible to enhance the intensity of most high harmonics in orders of magnitude. A most striking feature in the enhancement is that the intensity of several special high harmonics is practically impaired as compared with that in the monochromatic case. The qualitative explanation to the great enhancement is that the additional high-frequency field can provide new transition paths for electrons to reach the continuum. The relative phase between the fundamental field and its third harmonic field also affects the intensity of high-order harmonics near the cutoff efficiently.     

Second Harmonic Generation of Femtosecond Laser at One Micron in a Partially Deuterated KDP

Partially deuterated KDP is an ideal nonlinear crystal for second-harmonic generation （SHG） of femtosecond lasers at 1 μm, which features with vanished group-velocity mismatch at its retracing point of phase-matching. We numerically investigate the characteristics of SHG with femtosecond lasers in a partially deuterated KDP, which shows that group-velocity dispersion plays an important role. This spectrally non-critical phase-matching configuration can support both high efficiency and large acceptance bandwidth.     

Formation of Optical Solitons in Nonlinear Photonic Crystal Waveguides

Relying on the huge group velocity dispersion available in photonic crystal (PC) waveguides, we observe the formation of both Bragg grating solitons and gap solitons in nonlinear PC waveguides in numericalexperiments. Also, we indicate the potential applications of optical solitons in optical limiting, optical delay, and pulse compression and the feasibility of observing optical solitons in practical experiments.     

Second Harmonic Generation under the Influence of the Earth’s Gravitational Field

The influence of the Earth’s gravitational field on a weakly relativistic electron involved in the process of generation of microwave radiation is evaluated. It is shown that such exposure leads to the generation of a second harmonic.     

Supercontinuum Generation in a Photonic Crystal Fibre

Nearly 1000-nm broad continuum from 390 nm to 1370 nm is generated in a 2-m long photonic crystal fibre. The maximum total power of supercontinuum is measured to be 60mW with the pumping power of 800mW output from a 200-fs Ti:sapphire laser. The evolution of the pumping light into supercontinuum is experimentally studied in detail. It is found that the mechanism for supercontinuum generation has direct relations with Raman effect and soliton effect, and the four-wave mixing plays an important role in the last phase of the supercontinuum generation.     

Equal-Amplitude Optical Pulse Generation from a Rational Harmonic Mode-Locked Fibre Laser

A simple technique for the generation of equal-amplitude high repetition rate pulses from a rational harmonic mode-locked fibre ring laser is demonstrated. The principle is based on the combination of the nonlinear characteristics of the modulator and the effect of rational harmonic mode-locking. The two sources act on each other and the integrated effect eventually leads to the pulse amplitude-equalization. We obtain amplitude-equalized short pulses up to the fifth-order rational harmonic mode-locking with an optimum bias level and modulation depth of the modulator, which demonstrates the efficiency of this method.     

Hybrid Atomic–Optical Quantum Gyrometry

JETP Letters - A “hybrid” atomic–optical scheme of an interferometer–gyroscope has been proposed and investigated. It is based on the ring configuration of a...     

Laser Phase Relations of High-Order Harmonic Generation

Laser phase relations of high-order harmonic generation （HHG） are calculated with the saddle point theory. The results show a two-peak structure including a symmetric and an asymmetric temporal distributions of the instantaneous frequency of HHG radiation. These distributions are fitted with Gaussian and polynomial functions, respectively. Two calculation formulae are presented to analyse attosecond x-rays with specified time duration and energy bandwidth in experiments.     

Effects of Pulse Durations on High-order Harmonic Generation

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Ionization and Harmonic Generation of Diatomic Molecular Ion

l.IntroductionRecentexPerimentshavcdemonstratedthehigh-orderharmonicgenerationinraregasandmoleculargas[1~'j.TherearemanytheoreticalpaPersdealingwithharmonicgen-erationofatom[6~8j,comparativelysPeaking,theoreticalworksabouttheharmonicgen-erationofmolecuIeareless[9j,esPeciallyabouttheevolutionofionizationandharmonicgenerationwiththeinternuclearseparation,andtherelationbetweenionizationandhar-monicgeneration.InthispaPerwegivesomenumericalresultsofdiatomicmolecularionirradiatedbyalinearlyPOlari…     

Enhancement of Plasma Nonlinearities and Generation of a Microwave–Terahertz Supercontinuum in the Field of Subterawatt Mid-Infrared Pulses

JETP Letters - The smallness of the velocity $$v$$ of laser-field-induced motion of electrons compared to the speed of light c is one of the fundamental physical factors limiting the efficiency of...     

Second Harmonic Generation from Electrically Polarized CdS_xSe_(1-x) Microcrystallite Doped Glass

1.IntroductionSecond--ordernonlinearopticalmaterialisonekindofthequitesignificantnonlinearmaterialswhichiswidelyusedinlaserandphotonicsyStems.Theoretically,themacrthscopicsecondharmonicgeneration(SHG)inmaterialswithinversionsymmetrysuchasglassesshouldbeforbiddenaccordingtononlinearopttes.However,Osterbergetal.LijandlaterTometal.[2]observedSHGfromtheGeOZ-dopedSiOZglassfibersilluminatedwithintense1.06Urnlaserbeamorwith1.06urnfundamentalandfrequency--doubledlaserbeamssimultaneously.Theyatt…     

Fifth—Order Harmonic Generation using a Coherent Controlled Two—Pulsed Optical Field

We have experimentally studied the characteristics of fifth-order harmonic radiation produced by two coherent femtosecond laser pulses with a changeable relative phase.The intensities of harmonic generation are found to increase with the coherent degree.In one optical Period,the temporal variation of harmonics exhibits an asymmetric characteristic,which is interpreted in terms of ionization theory and the deformation of the wave packets of fundamental field contribution to harmonic generation.     

Possibilities of Characterizing the Crystal Parameters of CdxHg1 – xTe Structures on GaAs Substrates by the Method of Generation of the Probe-Radiation Second Harmonic in Reflection Geometry

Physics of the Solid State - Results of numerical simulation and experimental data on recording azimuthal angular dependences of a second-harmonic signal reflected from...