Enhanced Čerenkov second-harmonic emission in nonlinear photonic structures

We study experimentally and theoretically the ?erenkov-type second-harmonic generation in a one-dimensional nonlinear photonic crystal. We demonstrate that the power of emitted second-harmonic can be enhanced 270 times by varying the angle of incidence of the fundamental beam such that the reciprocal lattice vector of the crystal can be used to compensate for the phase mismatch in the transverse direction enabling interaction in the nonlinear Bragg diffraction regime.     

Tailoring Čerenkov second-harmonic generation in bulk nonlinear photonic crystal

We investigate theoretically the ?erenkov-type second-harmonic generation in two-dimensional bulk nonlinear photonic crystal with longitudinal modulation of the χ((2)) nonlinearity. We show that in this scheme the ?erenkov radiation can be achieved simultaneously at multiple directions with comparable intensities. The angles of emission are controllable by the spatial modulation of the nonlinearity. We propose a design of the periodically poled domain pattern, which maximizes the efficiency of the second-harmonic emission.     

Domain-shape-based modulation of Čerenkov second-harmonic generation in multidomain strontium barium niobate

We study experimentally and numerically the second-harmonic ?erenkov emission with two different characteristic azimuthal intensity distributions in strontium barium niobate with a random structure of χ2 nonlinearity. We monitor in situ the ?erenkov emission during domain switching and show that a change of domain size and shape results in a fourfold azimuthal modulation of the ?erenkov cone.     

CČerenkov second-harmonic generation by nondiffracting Bessel beams in bulk optical crystals

A new method of optical second-harmonic generation (SHG) in bulk media is proposed, using Bessel beams which realize Cerenkov phase matching. Single-domain crystals are presently considered. For noncollinear emission the scheme has the advantage of achieving conversion efficiencies of typically about double those achieved with unfocused Gaussian beams, over the same temperature bandwidth. The harmonic radiation is analysed using a Hankel transform-based spectral method. Numerical examples are given based on the crystal KNbO3, and possible experimental arrangements are suggested for the practical implementation of this method.     

Phase matching in ?erenkov second-harmonic generation: a leaky-mode analysis

Use of leaky modes allows us to demonstrate very simply that ?erenkov second-harmonic generation is not free of phase matching. The ?erenkov phase-matching condition is derived for what is to our knowledge the first time. The way to overcome the difficulty linked with the divergence at infinity of the leaky modes is discussed.     

Analysis of two-dimensional photonic band gap structure with a rhombus lattice

The relative band gap for a rhombus lattice photonic crystal is studied by plane wave expansion method and high frequency structure simulator(HFSS)simulation.General wave vectors in the first Briliouin zone are derived.The relative band gap as a function of air-filling factor and background material is investigated,respectively,and the nature of photonic band gap for different lattice angles is analyzed by the distribution of electric energy.These results would provide theoretical instruction for designing optical integrated devices using photonic crystal with a rhombus lattice.     

Polarization of Čerenkov radiation in anisotropic media

Using the method of Stokes parameters, we examine the polarization of erenkov radiation in anisotropic media. The study reveals that the radiation is totally polarized and that circular polarization is purely a quantum effect. We examine two cases: when the particle initially moves along the optical axis and when the particle initially moves perpendicular to the optical axis.     

Vavilov-Čerenkov radiation in dielectric and magnetic crystals

Relations are derived for the angular and spectral density of the radiation of electrons moving in crystals, the optical properties of which are described by symmetrical tensors of the dielectric constant and permeability.     

Regimes and spectra of čerenkov beam instability in a nonlinear plasma

We study the nonlinear evolution of an arbitrary initial disturbance due to the development of Čerenkov beam instability in a magnetized plasma-beam system of finite transverse size. Singleparticle, collective, and aperiodic regimes of this instability are considered. We calculate the nonlinear spatial spectra of the waves excited at different development stages of the beam instability in a plasma for the cases of quasi-monochromatic, pulsed, and noise initial disturbances. We analyze the formation and decay of regular structures in the beam and plasma at the developed nonlinear stage of the process. We find that plasma nonlinearity leads to the transfer of disturbance energy to the short-wave region of the spectrum. We show that, due to the development of beam instability, noise initial disturbance tends to become more monochromatic, whereas the shape of a pulsed one tends to remain unchanged. Transformation of monochromatic spatial disturbances into quasi-monochromatic plasma waves due to the instability development is analyzed. Institute of General Physics of the Russian Academy of Sciences, Moscow, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 42, No. 10, pp. 958–976, October 1999.     

Nonlinear elastic waves in a monatomic chain with nonlinear interactionReceived

Nonlinear wave equation for a one-dimensional anharmonic crystal lattice in terms of its microscopic parameters is obtained by means of a continuum approximation. Using a small time scale transformation, the nonlinear wave equation is reduced to a combine     

Nonlinear elastic waves in a monatomic chain with nonlinear interaction

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Characteristics of local photonic state density in an infinite two-dimensional photonic crystal

The local density of photonic states （LDPS） of an infinite two-dimensional （2D） photonic crystal （PC） composed of rotated square-pillars in a 2D square lattice is calculated in terms of the plane-wave expansion method in a combination with the point group theory. The calculation results show that the LDPS strongly depends on the spatial positions. The variations of the LDPS as functions of the radial coordinate and frequency exhibit “mountain chain” structures with sharp peaks. The LDPS with large value spans a finite area and falls abruptly down to small value at the position corresponding to the interfaces between two different refractive index materials. The larger/lower LDPS occurs inward the lower/larger dielectric-constant medium. This feature can be well interpreted by the continuity of electricdisplacement vector at the interface. In the frequency range of the pseudo-PBG （photonic band gap）, the LDPS keeps very low value over the whole Wiger-Seitz cell. It indicates that the spontaneous emission in 2D PCs cannot be prohibited completely, but it can be inhibited intensively when the resonate frequency falls into the pseudo-PBG.     

Absolute band gaps in two-dimensional graphite photonic crystal

The off-plane propagation of electromagnetic (EM) waves in a two-dimensional (2D) graphite photonic crystal structure was studied using transfer matrix method. Transmission spectra calculations indicate that such a 2D structure has a common band gap from 0.202 to 0.2035 c/a for both H and E polarizations and for all off-plane angles form 0° up to 90°. The presence of such an absolute band gap implies that 2D graphite photonic crystal, which is much easier and more feasible to fabricate, can exhibit some properties of a three-dimensional (3D) photonic crystal.     

Splitting of Vavilov-Čerenkov radiation spectra in excited dispersing media

Within the framework of quantum electrodynamics, the additional mechanism of shaping Vavilov-erenkov radiation, characteristic for excited media and not described by their refractive index, is examined. Its interference with the usual generation channel under stationary homogeneous conditions can eliminate the spectrum splitting detected earlier theoretically. Splitting is restored in inhomogeneous situations. The time inhomogeneity is analyzed.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 14–19, July, 1988.     

The measurement of bending wave intensity in a two-dimensional structure

I.IntroductionOfallstructuralwaves,bendingwaveismostimportant.Itiseasilyexcitedandresultsinairbornenoiseradiation'Inpractice,itisnecessarytodeterminetheenergydistributionandpowertransmissionincoupledstructl1res.Bendingwaveenergycanbecalculatedfrombendingwaveaccelerationwhilebendingwavepowertransmissionischaracterizedbybendingwaveintensitywhichisavectorgivillgthemagnitudeanddirection.TheengineeringaPplicationofthevectorpropertyofbendingwaveilltensityisnumerous[1~3]buttheinvestigationinitispre…     

Optical multistability in 1D photonic crystals with nonlinear Thue–Morse structure

A 1D photonic crystal structure contains 16 layers, 8 common dielectric layers and 8 layers with nonlinear medium, with an arrangement similar to the 5th generation, Thue–Morse multilayer is presented. The properties of photonics band gap, field distribution and optical multistability are investigated. On the band gap, 5 resonant modes is observed. On the behavior of output intensity versus input intensity around resonant frequencies, the multistability response observed. When the frequency of incident field is close to the resonant frequency, the threshold intensity of multistability is decreased.