Negative refraction at optical frequencies in nonmagnetic two-component molecular media

There is significant motivation to develop media with negative refractive indices at optical frequencies, but efforts in this direction are hampered by the weakness of the magnetic response at such frequencies. We show theoretically that a nonmagnetic medium with two atomic or molecular constituents can exhibit a negative refractive index. A negative index is possible even when the real parts of both the permittivity and permeability are positive. This surprising result provides a route to isotropic negative-index media at optical frequencies.     

Interaction of counterpropagating few cycle light pulses in nonlinear dielectric media and radiation generation at combination frequencies in this process

The regularities of the interaction of counterpropagating optical pulses of only a few oscillations of the light field in nonlinear dielectric media are studied theoretically. The temporal structure of the pulse field, due to its interaction with the counterpropagating pulse, is shown to be varied such that the field zeros are the most shifted in time and its extreme values are not shifted. The center of mass of the spectral density is shifted to the short-wavelength region. The efficiency of these phenomena is determined by the energy of the counterpropagating pulse and does not depend on its duration and spectral composition. The possibility of wave generation at tripled and combination frequencies is demonstrated for the media whose size is less than the interaction region. The efficiency of this generation with respect to the phase mutual modulation is shown to be increasing with a decrease in the number of oscillations in colliding pulses.     

Electric and magnetic optical response of dielectric nanospheres: Optical forces and scattering anisotropy

Nanospheres made of non-magnetic materials are shown to present non-conventional scattering properties similar to those previously reported for somewhat hypothetical magnetodielectric particles. We find a wide window in the near-infrared, where light scattering by lossless submicrometer semiconductor nanospheres is fully described by their induced electric and magnetic dipoles. The interference between electric and magnetic dipolar fields is shown to lead to anisotropic angular distributions of scattered intensity, including zero backward and almost zero forward scattered intensities at specific wavelengths. Interesting new consequences for the corresponding optical forces are derived from the interplay, both in and out of resonance, between the electric- and magnetic-induced dipoles.     

The ionic contribution to the nonlinear polarizability of a crystal at optical frequencies

It is shown that the ionic mechanism contributes negligibly to the part of the polarization at frequency 2. This is deduced from formulas previously derived from the microscopic theory of the nonlinear polarizability.     

The conduction regime in a nematic liquid crystal with negative dielectric anisotropy at frequencies above the dielectric relaxation frequency

Due to the relaxation of the longitudinal dielectric constant, the dielectric anisotropy in a nematic liquid crystal may change sign and become negative. This gives rise to a conduction regime with negative dielectric anisotropy at high frequencies. The width and cutoff frequency of this conduction regime are calculated.     

Excitation of oscillations in a hemispherical dielectric resonator by a radial magnetic dipole

Forced oscillations excited by a radial magnetic dipole in a dielectric hemisphere (resonator) placed on a perfectly conducting plane are studied. It is shown that the dipole excites H modes. When the dipole radiation frequency equals the eigenfrequency of the resonator, an amplitude resonance is observed in the spectrum. The excitation efficiency is high when the magnetic dipole is placed at the maximum of the radial field component of the resonator’s eigenmode.     

Intense laser effects on nonlinear optical absorption and optical rectification in single quantum wells under applied electric and magnetic field

In this work the effects of intense laser on the electron-related nonlinear optical absorption and nonlinear optical rectification in GaAs-Ga_1−xAl_xAs quantum wells are studied under, applied electric and magnetic field. The electric field is applied along the growth direction of the quantum well whereas the magnetic field has been considered to be in-plane. The calculations were performed within the density matrix formalism with the use of the effective mass and parabolic band approximations. The intense laser effects are included through the Floquet method, by modifying the confining potential associated to the heterostructure. Results are presented for the nonlinear optical absorption, the nonlinear optical rectification and the resonant peak of these two optical processes. Several configurations of the dimensions of the quantum well, the applied electric and magnetic fields, and the incident intense laser radiation have been considered. The outcome of the calculation suggests that the nonlinear optical absorption and optical rectification are non-monotonic functions of the dimensions of the heterostructure and of the external perturbations considered in this work.     

Saturation of the magnetic response of split-ring resonators at optical frequencies

We investigate numerically the limits of the resonant magnetic response with a negative effective permeability mu(eff) for single-ring multicut split-ring resonator (SRR) designs up to optical frequencies. We find the breakdown of linear scaling due to the free electron kinetic energy for frequencies above approximately 100 THz. Above the linear scaling regime, the resonance frequency saturates, while the amplitude of the resonant permeability decreases, ultimately ceasing to reach negative value. The highest resonance frequency at which mu(eff) < 0 increases with the number of cuts in the SRR. A LC circuit model provides explanation of the numerical data.     

Multimodal nonlinear optical polarizing microscopy of long-range molecular order in liquid crystals

We demonstrate orientation-sensitive multimodal nonlinear optical polarizing microscopy capable of probing orientational, polar, and biaxial features of mesomorphic ordering in soft matter. This technique achieves simultaneous imaging in broadband coherent anti-Stokes Raman scattering, multiphoton excitation fluorescence, and multiharmonic generation polarizing microscopy modes and is based on the use of a single femtosecond laser and a photonic crystal fiber as sources of the probing light. We show the viability of this technique for mapping of three-dimensional patterns of molecular orientations and show that images obtained in different microscopy modes are consistent with each other.     

非线性介质光波导中的传输功率和光学双稳态

本文对结构为非线性包层/线性芯层/非线性衬底的非线性介质光波导的传输特性进行了深入的分析,给出了模场分布函数,色散关系和传输功率的一组形式统一的公式,并对其传输功率的光学双稳态特性进行了讨论.     

Surface plasmon-assisted optical switching/bistability at telecommunication wavelengths in nonlinear dielectric gratings

In this paper, we numerically investigate nonlinear optical responses in dielectric gratings coated by flat metallic surface, where the structural parameters are chosen for wavelengths of operation at the telecom regime. The presented designs show the output light reflection with respect to the incident intensity of increasing, decreasing, and non-monotonic belt-shape functions. Nonlinear optical responses including switching and bistability appeared in the telecom region owing to assistance of surface plasmon resonance excited at the metal/dielectric interface, which enhances the diffraction efficiency and induces the momentum matching for the leaky modes of the dielectric grating. This results in electric intensity-effective refractive index dependence enhancement in the Kerr nonlinear media. Our design and investigation of the linear and nonlinear optical responses will provide a general guideline for a hybrid metallic-dielectric structure-based optical switching/bistability device design.     

Intense interactions of molecules with a short-wavelength electromagnetic radiation field: II. Resonance scattering of radiation and fluorescence

Within the framework of the nonadiabatic approach developed in the preceding paper, the resonance scattering, resonance Raman scattering, and resonance fluorescence are studied in detail for diatomic and triatomic molecules, and polyatomic symmetric and antisymmetric top molecules, which interact with the field of short-wavelength radiation with a wavelength λ ≥ Å and an intensity up to 10¹⁴ W/cm². The coherent excitations of high-lying Rydberg and autoionizing states are taken into account. Analytical expressions for calculating the tensors and cross sections of the above processes are derived.     

Metamaterial-based source and scattering enhancements: From microwave to optical frequencies

A brief review of metamaterial applications to source and scattering problems in the microwave and optical frequency regimes is given. Issues associated with modelling these systems are discussed. Electrically small radiating and scattering systems are emphasized. Single negative, double negative, and zero-index versions of these metamaterial-based systems are introduced that provide a means to manipulate their efficiency, bandwidth, and directivity characteristics.     

Bistatic scattering by arbitrarily shaped objects with rough surface at optical and infrared frequencies

The scattering cross sections for arbitrarily shaped dielectric objects with rough surface are determined for optical and infrared frequencies using the Kirchhoff approximation. The formula of the coherent scattering cross section is derived, and numerical method of incoherent scattering cross section is given. As a specific example, the infrared laser scattering cross sections of rough spheres are calculated at 1.06 m.