The term photonic crystals appears because of the analogy between electron waves in crystals and the light waves in artificial periodic dielectric structures. During the recent years the investigation of one-, two-and three-dimensional periodic structures has attracted a widespread attention of the world optics community because of great potentiality of such structures in advanced applied optical fields. The interest in periodic structures has been stimulated by the fast development of semiconductor technology that now allows the fabrication of artificial structures, whose period is comparable with the wavelength of light in the visible and infrared ranges.

http://ieeexplore.ieee.org/iel5/6354/16969/00781867.pdf

Photonic crystals

인공고관절의 세라믹 볼 헤드의 기계적 안정성 평가를 위한 3 차원 유한요소 해석

Two-photon excitation provides a means of activating chemical or physical processes with high spatial resolution in three dimensions and has made possible the development of three-dimensional fluorescence imaging, optical data storage, and lithographic microfabrication. These applications take advantage of the fact that the two-photon absorption probability depends quadratically on intensity, so under tight-focusing conditions, the absorption is confined at the focus to a volume of order λ3 (where λ is the laser wavelength). Any subsequent process, such as fluorescence or a photoinduced chemical reaction, is also localized in this small volume. Although three-dimensional data storage and microfabrication have been illustrated using two-photon-initiated polymerization of resins incorporating conventional ultraviolet-absorbing initiators, such photopolymer systems exhibit low photosensitivity as the initiators have small two-photon absorption cross-sections (δ). Consequently, this approach requires high laser power, and its widespread use remains impractical. Here we report on a class of π;-conjugated compounds that exhibit large δ (as high as 1, 250 × 10−50 cm4 s per photon) and enhanced two-photon sensitivity relative to ultraviolet initiators. Two-photon excitable resins based on these new initiators have been developed and used to demonstrate a scheme for three-dimensional data storage which permits fluorescent and refractive read-out, and the fabrication of three-dimensional micro-optical and micromechanical structures, including photonic-bandgap-type structures.

Two-photon polymerization initiators for three-dimensional optical data storage and microfabrication

This article reviews recent theoretical and experimental advances in the fundamental understanding and active control of quantum fluids of light in nonlinear optical systems. In the presence of effective photon-photon interactions induced by the optical nonlinearity of the medium, a many-photon system can behave collectively as a quantum fluid with a number of novel features stemming from its intrinsically nonequilibrium nature. A rich variety of recently observed photon hydrodynamical effects is presented, from the superfluid flow around a defect at low speeds, to the appearance of a Mach-Cherenkov cone in a supersonic flow, to the hydrodynamic formation of topological excitations such as quantized vortices and dark solitons at the surface of large impenetrable obstacles. While the review is mostly focused on a specific class of semiconductor systems that have been extensively studied in recent years (planar semiconductor microcavities in the strong light-matter coupling regime having cavity polaritons as elementary excitations), the very concept of quantum fluids of light applies to a broad spectrum of systems, ranging from bulk nonlinear crystals, to atomic clouds embedded in optical fibers and cavities, to photonic crystal cavities, to superconducting quantum circuits based on Josephson junctions. The conclusive part of the article is devoted to a review of the future perspectives in the direction of strongly correlated photon gases and of artificial gauge fields for photons. In particular, several mechanisms to obtain efficient photon blockade are presented, together with their application to the generation of novel quantum phases.

Quantum fluids of light

This paper reviews the recent theoretical and experimental advances in the study of ultra-cold gases made of bosonic particles interacting via the long-range, anisotropic dipole–dipole interaction, in addition to the short-range and isotropic contact interaction usually at work in ultra-cold gases. The specific properties emerging from the dipolar interaction are emphasized, from the mean-field regime valid for dilute Bose–Einstein condensates, to the strongly correlated regimes reached for dipolar bosons in optical lattices. (Some figures in this article are in colour only in the electronic version)

https://iopscience.iop.org/article/10.1088/0034-4885/72/12/126401/pdf

The physics of dipolar bosonic quantum gases

We demonstrate theoretically and experimentally the manipulation of spatial localized structures (spatial solitons) of a laser with saturable absorber in a self-imaging resonator. We show the on-off bistability of the solitons, their movement by phase gradient forces, the parameters of their existence, the limits of their stability, and periodic soliton nucleation and dynamics.

Spatial soliton laser: Localized structures in a laser with a saturable absorber in a self-imaging resonator

Temporal periodic modulation of the interatomic s-wave scattering length in Bose-Einstein condensates is shown to excite subharmonic patterns in the atom density through a parametric resonance. The dominant wavelength of the spatial structures is primarily selected by the excitation frequency but also affected by the depth of the spatial modulation via a nonlinear resonance. These phenomena represent analogues of the Faraday patterns excited in vertically vibrated liquids.

Faraday patterns in bose-Einstein condensates.

We investigate nondiffractive propagation of electromagnetic radiation, including visible light, through materials with a periodic space modulation of the refraction index, i.e., through photonic crystals. We calculate analytically and numerically the regimes where the dominating order of diffraction vanishes, i.e., the light beams of arbitrary width propagate without diffractive broadening and, equivalently, arbitrary light patterns can propagate without diffractive ``smearing.'' We investigate the subdiffractive light propagation, where the propagation is governed by the higher (fourth) diffraction order, when the dominating order of diffraction vanishes.

Nondiffractive propagation of light in photonic crystals.

A laser Ginzburg-Landau equation with fourth- and higher-order diffusion terms is derived from the Maxwell-Bloch equations describing a laser. It is shown that the higher-order diffusion terms in the laser Ginzburg-Landau equation are crucial for the transverse structure formation. Laser-hydrodynamical equations are derived, and the correspondence between laser light dynamics and the dynamics of a compressible, viscous, quantized fluid is demonstrated.

Laser Ginzburg-Landau equation and laser hydrodynamics.

Order Parameter Equations for Lasers.- Order Parameter Equations for Other Nonlinear Resonators.- Zero Detuning: Laser Hydrodynamics and Optical Vortices.- Finite Detuning: Vortex Sheets and Vortex Lattices.- Resonators with Curved Mirrors.- The Restless Vortex.- Domains and Spatial Solitons.- Subcritical Solitons I: Saturable Absorber.- Subcritical Solitons II: Nonlinear Resonance.- Phase Domains and Phase Solitons.- Turing Patterns in Nonlinear Optics.- Three-Dimensional Patterns.- Patterns and Noise.

Kestutis Staliunas

Papers

Spatial soliton laser: Localized structures in a laser with a saturable absorber in a self-imaging resonator

Faraday patterns in bose-Einstein condensates.

Nondiffractive propagation of light in photonic crystals.

Laser Ginzburg-Landau equation and laser hydrodynamics.

Transverse Patterns in Nonlinear Optical Resonators