A concept of the remotely actuated and interrogated four-wave mixing photonic sensor, which employs the negative-index photonic materials, is described. Unique electromagnetic properties of such a metamaterial enable enhancement of frequency conversion and redirection of the signals which carry important information for environmental probing. Four-wave mixing process allows for independent engineering of resonantly enhanced optical nonlinearities and negative refractive index.
A concept of a family of unique backward-wave photonic devices, such as frequency up and down converting nonlinear-optical mirrors, sensors, modulators, filters and amplifiers is proposed. Novel materials are considered, which support coexistence of ordinary and backward waves and thus enable enhanced nonlinear-optical frequency conversion processes. Particular properties of short-pulse regime are investigated.
The extraordinary properties of nonlinear optical propagation processes in double-domain positive/negative
index metamaterials are reviewed. These processes include second harmonic generation, three- and four-wave
frequency mixing, and optical parametric amplification. Striking contrasts with the properties of the counterparts
in ordinary materials are shown. We also discuss the possibilities for compensating strong losses inherent to
plasmonic metamaterials, which present a major obstacle in numerous exciting applications, and the possibilities
for creation of unique ultracompact photonic devices such as data processing chips and nonlinear-optical sensors.
Finally, we propose similar extraordinary three-wave mixing processes in crystals based on optical phonons with
negative dispersion.
The concept of all-optically controlled, remotely actuated and interrogated, ultra-compact nonlinear-optical sensor
which can be employed for environmental probing in remote or hostile locations is proposed and the underlying
theory is developed. Backwardness of electromagnetic waves propagating in the negative-index metamaterials
play critically important role in the proposed concept. Difference-frequency, three- and four-wave mixing processes
are investigated and numerically simulated, which utilize uncommon coherent energy transfer from the
control optical field to the contra-propagating negative-phase wave. Such conversion leads to parametric amplification
of the incident signal and frequency-shifted wave generated in the direction of reflection. Extraordinary
features of the proposed microscopic devices applied to sensing applications are discussed. Numerical experiments
have been carried out to identify optimum operational requirements and the anticipated properties of the
proposed sensor.
The feasibilities and specific features of coherent nonlinear-optical energy transfer from control fields to a negativephase
signal are studied, and they are found to stem from the backwardness of electromagnetic waves inherent
to negative-index metamaterials. Plasmonic metamaterials that possess negative group velocity for light waves
promise a revolutionary breakthrough in nanophotonics. However, strong absorption inherent to such metaldielectric
nanocomposites imposes severe limitations on the majority of such applications. Herein we show the
feasibility and discuss different nonlinear-optical techniques of compensating such losses, producing transparency,
amplification and even generation of negative-phase light waves in originally strongly absorbing microscopic
samples of plasmonic metal-dielectric nanostructured composites.
Interactive numerical simulator, based on MATLAB/SIMULINK platform, for virtual experimentation and optimization of frequency tunable optically pumped dimer laser has been created. Nonperturbative theory considering features of quantum coherence and interference effects at Doppler broadened transitions under two strong driving fields accounting for collisions and other kinetic processes in vapor-gas mixture as well as for propagation effects in optically thick medium is developed. The results are in good agreement with real experiments.
We theoretically study cw two-photon resonant four-wave mixing process (formula available in paper) when fundamental radiation with frequencies (formula available in paper) are strong enough and lead to coherent population trapping (CPT). It is shown that under conditions of CPT, the linear and nonlinear polarization can be the same order. Efficient nonlinear frequency conversion in atomic Ba vapor in cw regime is demonstrated.
The possibility of elimination of Doppler broadening and simultaneous coherent coupling of atoms from wide velocity intervals in three-photon schemes is shown. A simple physical analysis in terms of modification of frequency- correlation properties of multiphoton processes in strong fields is given. Numerical illustrations are presented.
Appearance of coherence effects in resonant Raman and double-A schemes appropriate to the cw experiments on Doppler-broadened transitions of Na2 and I2 molecules is discussed. Possibilities for manipulating the resonance shape in optically thick Doppler-broadened media with effects of quantum interference, as well as elimination of Doppler broadening in strong driving fields are outlined.
Manifestations of two photon photo-effect at illumination intensities on the order of solar light (10-3 W/cm2) were observed for the first time. We believe that it is due giant enhancement of the nonlinear effects in the local fields, inherent to fractal nano-structures.
We study resonant four-wave mixing process (omega) 4 equals (omega) 1 minus (omega) 2 plus (omega) 3 under conditions of coherent population trapping (CPT) when radiations with frequencies (omega) 1,2 are strong, and (omega) 1 minus (omega) 2 equals (omega) 20 ((omega) 20 is a frequency of electrodipole-forbidden transition). It is shown that under the CPT sufficiently large nonlinear polarization (the same as linear polarization or higher) may be created. We show that in atomic Ba vapor for cw lasers quantum conversion efficiency can be as high as several tens percent.
An influence of nonlinear interference processes at quantum transitions in strong resonance electromagnetic fields on absorption, amplification and refractive indices as well as on four-wave mixing processes is investigated. Doppler broadening of the coupled transitions, incoherent excitation, relaxation processes, as well as power saturation processes associated with the coupled levels are taken into account. Both closed (ground state is involved) and open (only excited states are involved) energy level configurations are considered. Common expressions are obtained which allow to analyze the optical characteristics (including gain without inversion and enhanced refractive index at vanishing absorption) for various V, (Lambda) and H configurations of interfering transitions by a simple substitution of parameters. Similar expressions for resonant four-wave mixing (FWM) in Raman configurations are derived too. Crucial role of Doppler broadening is shown. Theory is applied for numerical analysis of some recent and potential experiments.
Interference effects in quantum transitions, giving rise to amplification without inversion, optical transparency and to enhancements in nonlinear optical frequency conversions are considered. Review of the relevant early theoretical and experimental results is given. The role of relaxation processes, spontaneous cascade of polarizations, local field effects, Doppler- broadening, as well as specific features of the interference in the spectral continuum are discussed.
Double-lambda four-level configuration, coupled to two driving and two probe fields is considered. Explicit formulae, based on density-matrix approach, for the analysis of the conditions of amplification without population inversion both in V and (Lambda) configurations are given. Effects of inhomogeneous broadening of the transitions on coherent coupling are discussed. Crucial importance of these effects for the choice of the proper transition schematics is shown. Numerical analysis of the conditions for amplification without inversion and four-wave mixing in the Ne energy-level configuration, relevant to the experiments, which are under way, is given.
Giant increase (up to 1010 times) of aggregation rate of silver colloids to the fractal structures under influence of optical radiation is found. Spectral, temporal and energy characteristics of the process are investigated. The instantaneous spectral changes are explained by the influence of laser-induced far-ranged electrostatic forces on the fractal aggregation and by the subsequent fractal photomodification.
This paper is aimed at discussing the basic principles of light-induced drift (LID) and estimating the characteristic of the effect, produced by quasi-black-body radiation. Many astrophysical objects as well as laser-produced plasmas may be described by that model in the first approximation. The feasibility is analyzed of converting the radiation of the most efficient cw laser (a technological CO2 laser) via laser-produced plasma into a broad-band radiation to be used as a source of LID of a wide range of substances.
Dynamic orientation of anisotropic molecules in a gas-phase medium under the action of laser pulses of a duration shorter than the rotation relaxation time has been studied both theoretically and experimentally. The effect was observed in the VUV third-harmonic generation in naphthalene vapor. The peculiarities of nonlinear optical UV and VUV generation (by frequency mixing of Nd-laser radiation) in the vapors of some compounds are studied.
The paper studies the process of photostimulated aggregation of ultradispersoidal silver particles into fractal clusters observed in some colloidal solutions irradiated by different types of pulsed and continuous-wave lasers and by a nonmonochromatic light. A photoaggregaton mechanism has been proposed, based on mutual charging of different-size particles in a conducting medium when the Fermi potentials become equal because of their dimensional dependence.
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