Unidirectional amplification and shaping of optical pulses by three-wave mixing with negative phonons

A possibility to greatly enhance frequency-conversion efficiency of stimulated Raman scattering is shown by making use of extraordinary properties of three-wave mixing of ordinary and backward waves. Such processes are commonly attributed to negative-index plasmonic metamaterials. This work demonstrates the possibility to replace such metamaterials that are very challenging to engineer by readily available crystals which support elastic waves with contra-directed phase and group velocities. The main goal of this work was to investigate specific properties of indicated nonlinear optical process in short-pulse regime and to show that it enables elimination of fundamental detrimental effect of fast damping of optical phonons on the process concerned. Among the applications is the possibility of creation of a family of unique photonic devices such as unidirectional Raman amplifiers and femtosecond pulse shapers with greatly improved operational properties.     

Negative group velocity and three-wave mixing in dielectric crystals

We investigate extraordinary features of optical parametric amplification of Stokes electromagnetic waves that originate from the three-wave mixing of a backward phonon wave with negative group velocity and two ordinary electromagnetic waves. Such properties were earlier shown to exist only in plasmonic negative-index metamaterials that are very challenging to fabricate. Nonlinear optical photonic devices with properties similar to those predicted for negative-index metamaterials are proposed.     

Acoustic properties of globular photonic crystals based on synthetic opals

Acoustic properties of globular photonic crystals based on synthetic opals and composed of closely packed SiO₂ globules about 200 nm in diameter are theoretically investigated. Dispersion characteristics of the investigated samples are numerically simulated, and the group velocity of acoustic waves and the effective mass of acoustic phonons are found. It is shown that phononic bandgaps in these photonic crystals are within the gigahertz frequency range. The effective mass of the acoustic phonons corresponding to the edges of the bandgaps is found, and a possibility that bound states of acoustic phonon pairs, biphonons, manifest themselves in the light scattering spectra is discussed.     

Four-wave mixing, quantum control, and compensating losses in doped negative-index photonic metamaterials

The possibility of compensating absorption in negative-index metamaterials (NIMs) doped by resonant nonlinear-optical centers is shown. The role of quantum interference and the extraordinary properties of four-wave parametric amplification of counterpropagating electromagnetic waves in NIMs are discussed.     

Resonant nonlinear optics of backward waves in negative-index metamaterials

The extraordinary properties of resonant four-wave mixing of backward and ordinary electromagnetic waves in doped negative-index materials are investigated. The feasibility of independent engineering of the negative refractive index and the nonlinear optical response as well as quantum control of the nonlinear propagation process in such composites is shown due to the coherent energy transfer from a control field to a signal field. Laser-induced transparency, quantum switching, frequency-tunable narrow-band filtering, amplification, and realizing a miniature mirrorless optical parametric generator of the entangled backward and ordinary waves are among the possible applications of the investigated processes.     

From the inverted pendulum to the periodic interface modes

The physics of the spatial propagation of monochromatic waves in periodic media is related to the temporal evolution of the parametric oscillators. We transpose the possibility that a parametric pendulum oscillates in the vicinity of its unstable equilibrium position to the case of monochromatic waves in a lossless unidimensional periodic medium. We develop this concept, that can formally applies to any kind of waves, to the case of longitudinal elastic wave. Our analysis yields us to study the propagation of monochromatic waves in a periodic structure involving two main periods. We evidence a class of phonons we refer to as periodic interface modes that propagate in these structures. These modes are similar to the optical Tamm states exhibited in photonic crystals. Our analysis is based on both a formal and an analytical approach. The application of the concept to the case of phonons in an experimentally realizable structure is given. We finally show how to control the frequencies of these phonons from the engineering of the periodic structure.     

Homogenization of magnetodielectric photonic crystals

We calculate the low-frequency index of refraction of a medium which is homogeneous along axis z and possesses a periodic dependence of the permittivity epsilon(r) and permeability micro(r) in the x-y plane (2D magnetodielectric photonic crystal). Exact analytical formulas for the effective index of refraction for two eigenmodes with vector E or H polarized along axis z are obtained. We show that, unlike nonmagnetic photonic crystals where the E mode is ordinary and the H mode is extraordinary, now both modes exhibit extraordinary behavior. Because of this distinction, the magnetodielectric photonic crystals exhibit optical properties that do not exist for natural crystals. We also discuss the limiting case of perfectly conducting cylinders and clarify the so-called problem of noncommuting limits, omega-->0 and epsilon--> infinity.     

Optics of Photonic Crystals

In this article, a general theoretical framework to describe and analyze the optical properties of photonic crystals is presented. In addition to the analytical treatment of their optical response based on the method of Green’s function, numerical tools to calculate the dispersion relations and the eigenfunctions of the radiation field, transmission spectra, localized midgap modes, and lasing threshold are introduced and applied to some typical examples. Group theory to analyze the symmetry of the eigenmodes is also introduced, and the existence of uncoupled modes that cannot be excited by external plane waves is shown. The presence of the enhancement effect of nonlinear optical processes and stimulated emission due to the small group velocity which is easily realized in the photonic crystals is pointed out, and the possibility of low-threshold lasing in the photonic crystals is discussed.     

Negative-index metamaterials: second-harmonic generation, Manley–Rowe relations and parametric amplification

Second harmonic generation and optical parametric amplification in negative-index metamaterials (NIMs) are studied. The opposite directions of the wave vector and the Poynting vector in NIMs results in a “backward” phase-matching condition, causing significant changes in the Manley–Rowe relations and spatial distributions of the coupled field intensities. It is shown that absorption in NIMs can be compensated by backward optical parametric amplification. The possibility of distributed-feedback parametric oscillation with no cavity has been demonstrated. The feasibility of the generation of entangled pairs of left- and right-handed counter-propagating photons is discussed. PACS 78.67.-n; 42.65.Ky; 42.65.Lm     

Nonlinear optics of backward waves and extraordinary features of plasmonic nonlinear-optical microdevices

Extraordinary properties and unique features of coherent nonlinear-optical coupling of ordinary and backward electromagnetic waves in negative-index metamaterials are described and numerically simulated. The possibility for design of unique microscopic photonic devices and all-optical data processing chips is shown.     

Slow light in photonic crystals

The problem of slowing down light by orders of magnitude has been extensively discussed in the literature. Such a possibility can be useful in a variety of optical and microwave applications. Many qualitatively different approaches have been explored. Here we discuss how this goal can be achieved in linear dispersive media, such as photonic crystals. The existence of slowly propagating electromagnetic waves in photonic crystals is quite obvious and well known. The main problem, though, has been how to convert the input radiation into the slow mode without losing a significant portion of the incident light energy to absorption, reflection, etc. We show that the so-called frozen mode regime offers a unique solution to the above problem. Under the frozen mode regime, the incident light enters the photonic crystal with little reflection and, subsequently, is completely converted into the frozen mode with huge amplitude and almost zero group velocity. The linearity of the above effect allows the slowing of light regardless of its intensity. An additional advantage of photonic crystals over other methods of slowing down light is that photonic crystals can preserve both time and space coherence of the input electromagnetic wave.     

Bound states in the continuum in metal—dielectric photonic crystal with a birefringent defect

By using the difference of the band structure for the TE and TM waves in the metal—dielectric photonic crystals beyond the light cone and the birefringence of the anisotropic crystal, a one-dimensional photonic system is constructed to realize the bound states in the continuum (BICs). In addition to the BICs arising from the polarization incompatibility, the Friedrich—Wintgen BICs are also achieved when the leaking TM wave is eliminated due to the destructive interference of its ordinary and extraordinary wave components in the anisotropic crystal. A modified scheme favorable for practical application is also proposed. This scheme for BICs may help to suppress the radiation loss in the metal—dielectric photonic crystal systems.     

Polarization-anisotropic scattering lines in LiNbO3

Lines of light-induced scattering with extraordinary polarization from two ordinary polarized pump waves in LiNbO₃:Fe crystals are observed. A nonlinear mixing of four copropagating waves in the crystal with photovoltaic charge transport is shown to be the reason for parametric amplification of the seed radiation scattered from optical imperfections of the sample.     

Backward ion‐acoustic waves in plasma with unidirectional ion flow

This paper considers ion‐acoustic waves in a plasma in which the ions move unidirectionally. The dispersion equation is considered and analysed as a two‐dimensional problem. It is shown that the ion‐acoustic waves can be in the form of backward waves (BWs ). The area boundaries in the plane {k _x , k _y } where the BW exists are found.     

Optimal poling of nonlinear photonic crystals for frequency conversion

Nonlinear photonic crystals formed by two-dimensional periodic poling of the quadratic susceptibility chi(2) can support quasi-phase-matched harmonic generation. The frequency-conversion efficiency depends on the photonic crystal's poling pattern through certain Fourier coefficients of the poling function. A procedure is described for finding those poling patterns that are most efficient for any specific quasi-phase-matched frequency-conversion scheme.     

Self-modulation of light in piezoelectric crystals

Spectroscopic measurements were used to monitor the optical interference of ordinary (o-ray) waves with extraordinary (e-ray) waves by incidence of plane-polarized light and transmission through piezoelectriccrystals (alpha-quartz, LiNbO3, and LiTaO3). This observation confirms that the rotations of the vibration planes of the o- and e-ray waves originate from the dynamic gratings induced by the electric field of the incident light. This is a self-modulation process of the polarized incident light in piezoelectric crystals.     

光子晶体表面光波导的特性研究

采用平面波展开法和时域有限差分法,研究了光子晶体表面光波导的色散及光传输特性。研究结果表明,表面模的出现及其色散特性与表面介质柱的半径相关,色散曲线的斜率保持单调变化,并在最低或最高频率附近展现低群速度频率区。由于光子带隙和全内反射的共同影响,光场将沿晶体表面高效率地传输。研究结果为探索在光子晶体外部控制光传输具有重要的理论意义。     

Superprism effect based on phase velocities

The superprism effect has been studied in the past by use of the anomalous group velocities of optical waves in photonic crystals. We suggest the possibility of realizing agile beam steering based on purely phase-velocity effects. We present designs of photonic crystal prisms that might make experimental observation of this effect possible.     

Surface wave-induced enhancement of the Goos-Hänchen effect in one-dimensional photonic crystals

The excitation conditions of surface electromagnetic waves in one-dimensional photonic crystals (Bragg reflectors) are studied. Surface electromagnetic waves are visualized by the far-field optical microscopy of the surface of the photonic crystal. The enhancement of the Goos-Hänchen effect by surface electromagnetic waves excited in one-dimensional photonic crystals has been experimentally observed. The Goos-Hänchen shift reaches 30λ for a wavelength of λ = 532 nm.