Nonlinear Interaction Of Light Research Articles

Four‐Wave Mixing Holographic Multiplexing Based on Nonlinear Metasurfaces

AbstractMetasurfaces are utilized to realize computer‐generated holograms (CGHs), with excellent wavefront shaping ability and ultrasmall footprint. To increase the information capacity of metasurface holograms, smart multiplexing techniques together with suitable designs are highly demanded. However, so far only a few approaches to achieve nonlinear metasurfaces holographic multiplexing based on CGHs are proposed, due to limited freedoms of multiplexing and proper metasurfaces' design. The nonlinear interaction of light with the metasurface can generate new frequencies compared to the input laser beam, which is promising to realize spectral and spatial multifunctional wavefront manipulation. Here, a four‐wave mixing (FWM) holographic multiplexing technique is numerically proposed using a nonlinear metasurface composed of a nanoapertures array. It is demonstrated that the complex amplitude modulation by such a metasurface through the FWM process can be utilized for amplitude‐only CGHs, which can process significantly independent information at different nonlinear frequencies in the optical regime. Utilizing the spatial and spectral multiplexing of nonlinear metasurfaces holography, they can be found applications for multidimensional holographic displays and can provide enhanced security for optical data storage. These results show that nonlinear metasurfaces are promising for applications of arbitrary frequency conversion and optical encryption and anticounterfeiting designs.

Optical nonlinearities of small polarons in lithium niobate

An overview of optical nonlinearities of small bound polarons is given, which can occur in the congruently melting composition of LiNbO3. Such polarons decisively influence the linear and nonlinear optical performance of this material that is important for the field of optics and photonics. On the basis of an elementary phenomenological approach, the localization of carriers in a periodic lattice with intrinsic defects is introduced. It is applied to describe the binding energies of four electron and hole small polarons in LiNbO3: small free NbNb4+ polarons, small bound NbLi4+ polarons, small bound NbLi4+:NbNb4+ bipolarons, and small bound O− hole polarons. For the understanding of their linear interaction with light, an optically induced transfer between nearest-neighboring polaronic sites is assumed. It reveals spectrally well separated optical absorption features in the visible and near-infrared spectral range, their small polaron peak energies and lineshapes. Nonlinear interaction of light is assigned to the optical formation of short-lived small polarons as a result of carrier excitation by means of band-to-band transitions. It is accompanied by the appearance of a transient absorption being spectrally constituted by the individual fingerprints of the small polarons involved. The relaxation dynamics of the transients is thermally activated and characterized phenomenologically by a stretched exponential behavior, according to incoherent 3D small polaron hopping between regular and defect sites of the crystal lattice. It is shown that the analysis of the dynamics is a useful tool for revealing the recombination processes between small polarons of different charge. Nonlinear interaction of small polarons with light furthermore results in changes of the index of refraction. Besides its causal relation to the transients via Kramers-Kronig relation, pronounced index changes may occur due to optically generated electric fields modulating the index of refraction via the linear electro-optic effect, also. Based on a microscopic picture and by considering the local structural environment of bound polarons, the appearance of photovoltaic currents is explained straightforwardly as a result of the optically induced carrier transfer. Both transient absorption and index changes are spatially confined to the intensity profile of the interacting light allowing for the recording of efficient mixed absorption and phase volume holograms. By means of holographic spectroscopy, these small-polaron based optical nonlinearities are verified either without or with the action of the linear electro-optic effect; their prominent features are highlighted by appropriate experimental studies wherin the ultrafast response on the picosecond time scale is the most recognized one. Based on these findings, the consequences for applications of LiNbO3 in the field of nonlinear optics and photonics are presented. Besides visionary examples like real-time, 3D holographic displays, the impact of optical nonlinearities of small polarons for present applications are discussed with frequency conversion and respective limiting effects, such as green-induced infrared absorption and optical damage, as important example.

Nonlinear optics of fibre event horizons.

The nonlinear interaction of light in an optical fibre can mimic the physics at an event horizon. This analogue arises when a weak probe wave is unable to pass through an intense soliton, despite propagating at a different velocity. To date, these dynamics have been described in the time domain in terms of a soliton-induced refractive index barrier that modifies the velocity of the probe. Here we complete the physical description of fibre-optic event horizons by presenting a full frequency-domain description in terms of cascaded four-wave mixing between discrete single-frequency fields, and experimentally demonstrate signature frequency shifts using continuous wave lasers. Our description is confirmed by the remarkable agreement with experiments performed in the continuum limit, reached using ultrafast lasers. We anticipate that clarifying the description of fibre event horizons will significantly impact on the description of horizon dynamics and soliton interactions in photonics and other systems.

Research of Condensed Matter Physics Based on Ultrafast Spectroscopy

Ultrafast spectroscopy has many characteristics, which has attracted much attention in recent years. It is of high time resolution, rich nonlinear interaction of light and matter. It can be used to regulate the quantum state of matter coherent photons and its derivatives and grafting technology bring a lot of changes in condensed matter physics experiment technology. This article introduces the general principles time-resolved technique and typical configuration of ultrafast spectroscopy. Through specific examples this paper shows its applications in condensed matter physics research.

Nonlinear Nanowire Close to a Truncated Metallic Film: a Step Toward Nanosized Light Sources

A controllable nanosized light source based on nonlinear interaction of light and a semiconductor nanowire is proposed. Surface plasmon polariton (SPP) waves with different frequencies propagate along the upper and lower surfaces of a truncated metallic film and are scattered at its end face. A nanowire, in that vicinity, is pumped by the scattered light, and new harmonics are generated via second-order nonlinear optical effects. Green's function surface integral equation method is exploited to numerically calculate the electric field, the magnetic field, and the power of the generated frequency components. Results show that the power of the generated harmonics depends on the position and radius of the nanowire, thickness of the metallic film, as well as the wavelength of the incident SPP waves. On the other hand, by controlling the phase difference between incident SPP waves having the same frequencies, it is possible to manipulate the electric field pattern and also to change the power of the generated harmonics.

Nonlinear interaction of light with a Bose-Einstein condensate: Methods to generate sub-Poissonian light

We consider a $\ensuremath{\Lambda}$-type model of the Bose-Einstein condensate of sodium atoms interacting with the light. Coefficients of the Kerr nonlinearity in the condensate can achieve large and negative values, providing the possibility for effective control of group velocity and dispersion of the probe pulse. We find a regime when the observation of the ``slow'' and ``fast'' light propagating without absorption becomes achievable due to the strong nonlinearity. An effective two-level quantum model of the system is derived and studied. Our approach is based on a possibility of establishing a connection of the underlying algebra with the $su(2)$ algebra within the formalism of the polynomial algebras of excitations (PAE). We propose an efficient way for the generation of sub-Poissonian fields in the Bose-Einstein condensate at time-scales much shorter than the characteristic decay time in the system. We show that the quantum properties of the probe pulse can be controlled in BEC by the classical coupling field.

Intense X-Shaped Pulses of Light Propagate Without Spreading in Water and Other Dispersive Media

The nonlinear interaction of light with matter can imbue optical pulses with surprising and potentially useful properties.

Effect of optical activity on the self-focusing of light beams in cubic photorefractive crystals

The self-focusing of Gaussian light beams and the propagation of screening spatial solitons in a cubic optically active photorefractive crystal with the (1̄1̄0) cut plane are studied for an arbitrary orientation of an external electric field in this plane. A change in the rotation of the polarisation plane caused by the nonlinear interaction of light with the crystal is studied theoretically. It is shown that optical activity enhances self-focusing in some cases. Screening self-focusing was observed in an incoherently illuminated Bi12SiO20 crystal without additional laser irradiation. The experimental data well agree with the proposed theoretical model.

Space-time dynamics of nanoparticles of a magnetofluid in a laser beam

Laser-induced space-time dynamics of nanoparticles of a magnetofluid was observed. Visualization was effectuated and the redistribution of the particles was measured. These showed a strong decrease in the particle density on and around the periphery of the laser beam axis. A number of proofs showing that the thermal diffusion of nanoparticles plays the key role in determining the dynamics of the particle redistribution are presented. High-quality pictures taken of the self-modulation of the laser beam serve as a new and powerful method for investigating transport phenomena and the nonlinear interaction of light with colloids.

Nonlinear Interaction of Light with Transversely Moving Medium.

Interaction of a light beam with matter reveals extreme sensitivity to transverse motions. Spatio-temporal delocalization of interaction and diffusive transport of light-induced perturbations is revealed through a new family of diffraction patterns. The response of the medium to the transverse motion of the light enhances near the second order phase transition point. The phenomenon has large application potential for the study of motions that are beyond the power of Doppler-effect-based methods, and suggests fundamental problems about critical processes with nonstationary influences.

NEAR INFRARED NONLINEAR OPTICAL PHASE CONJUGATION IN PHOTOREFRACTIVE CRYSTALS AND SEMICONDUCTOR MATERIALS PART I: FUNDAMENTALS

The concept of optical wavefront reversing as a tool for phase aberration correction is reviewed. Presenting the fundamental and basic nature of the nonlinear interaction of light with matter leading to optical phase conjugation, a theoretical description of the photorefractive effect is given with a special emphasis on the gain of a coupling experiment and the speed of the photorefractive effect. Optical phase conjugation configurations, designs, and enhancement techniques are described and summarized comparing the possibilities and disadvantages regarding specific applications in the near infrared.

Non-Markov model of nonlinear interaction of light in a strongly couple electron-phonon system

Non-Markov model of nonlinear interaction of light in a strongly couple electron-phonon system

Investigation of the rotation of a wave front in a molecular multipass amplifier

Close attention has been focused on the phenomenon of the rotation of a wave front (RWF) which arises upon nonlinear interaction of light with matter in connection with the broad possibilities for its practical applications in contemporary laser technology. However, one can note the low energy efficiency of this phenomenon from the results of experimental investigations known up to this time in the various schemes for producing RWF. One of the interesting solutions of this problem is the accomplishment of RWF with four-photon mixing (FPM) in amplifying media. This process was first discussed theoretically in [i]. The experimental results [2] showed that in a multipass amplifier the "rotated" wave can exceed by several times the level of the incident wave.

A master equation approach to nonlinear optics

The nonlinear interaction of light with matter is described from a quantum-statistical point of view. The phenomena of two-photon emission and two-photon absorption including both the single- and two-mode cases and the Raman effect are discussed in detail. A master equation for the density operator of the light fields alone is derived. This operator equation is converted to a c number equation and analytic solutions are obtained for the diagonal matrix elements of the density operator in the Fock representation. No linearizing approximation is introduced. These solutions allow one to compute the moments of the photon distribution for the above nonlinear processes.

Quantum Statistics of Nonlinear Optics

Nonlinear interaction of light with matter is described from the quantum-statistical point of view. The cases of two-photon absorption, Raman transition, sum-frequency generation, parametric amplification, and incoherent scattering are discussed. It is shown that the nonlinear optical effects depend strongly on the statistical properties of the light fields. The rate of nonlinear absorption, generation, and amplification is higher for chaotic than for coherent, and also higher for multimode than for single-mode pump fields. Measurements of the statistics of the output fields may yield information about the statistics of the input fields and the properties of the medium.

Nonlinear Interaction of Light in a Plasma

Nonlinear Interaction of Light in a Plasma