Showing papers in "Progress in Optics in 2009"

Singular optics: optical vortices and polarization singularities

Abstract: Publisher Summary The widespread availability of spatially and temporally coherent laser sources makes the production of optical vortices inevitable in any experiment involving scattered laser light. The realization of quantized vortices is not specific to optics: these objects occur in all spatial scalar fields. Although optical vortices are often referred to as “points of phase singularity within a cross section of the field,” physical optical fields extend over three dimensions, and the phase singularities are actually lines of perfect destructive interference that are embedded in the volume filled by the light. Optical vortices are examples of the singularity lines within all complicated scalar fields. By comparison, electromagnetic vector fields do not generally have nodes in all components simultaneously. However, vector fields possess singularities associated with the parameterization of elliptical and partial polarization rather than phase. Polarization singularities are present in many situations, ranging from sunlight to the light transmitted by birefringent materials. Their descriptors are more complicated than their scalar counterpart in that they have both handedness and additional categorization. The study of optical vortices and orbital angular momentum has led to a recognition that the energy flow—characterized by the Poynting vector—has features not immediately apparent from the intensity alone, nor from global properties of a beam.

Transformation Optics and the Geometry of Light

Abstract: Publisher Summary This chapter describes the geometry of light and the concepts of transformation optics. Transformation optics is beginning to transform optics. The chapter introduces connections between geometry and electromagnetism in media that is as consistent and elementary as possible. This chapter analyzes four examples of transformation media—cloaking devices, perfect lenses, vortices, and horizons; these four cases illustrate characteristic non-trivial topologies, each one with different physics, and they have been experimentally verified. This chapter focuses on the main ideas and some connections between optics, in particular, transformation optics, and other areas of physics and mathematics. It also addresses the classical optics of transformation media.

Soliton Shape and Mobility Control in Optical Lattices

Abstract: We present a progress overview focused on the recent theoretical and experimental advances in the area of soliton manipulation in optical lattices Optical lattices offer the possibility to engineer and to control the diffraction of light beams in media with periodically-modulated optical properties, to manage the corresponding reflection and transmission bands, and to form specially designed defects Consequently, they afford the existence of a rich variety of new families of nonlinear stationary waves and solitons, lead to new rich dynamical phenomena, and offer novel conceptual opportunities for all-optical shaping, switching and routing of optical signals encoded in soliton formats In this overview, we consider reconfigurable optically-induced lattices as well as waveguide arrays made in suitable nonlinear materials We address both, one-dimensional and multi-dimensional geometries We specially target the new possibilities made possible by optical lattices induced by a variety of existing nondiffracting light patterns, we address nonlinear lattices and soliton arrays, and we briefly explore the unique features exhibited by light propagation in defect modes and in random lattices, an area of current topical interest and of potential cross-disciplinary impact

Coherent Backscattering and Anderson Localization of Light

Abstract: In this review we discuss localization of waves by multiple scattering. In the weak case, also known as coherent backscattering, there is a twofold enhancement of the reflected intensity in the back direction. We discuss the origin of this effect, its shape with reflection angle as well as the influence of finite sample size and absorption on this shape. This discussion of the properties of the coherent backscattering cone is based on experimental investigations of multiple scattering of light in various media over the last two decades. In addition, we discuss experiments on coherent backscattering using many other types of waves. In a second part, we discuss the experimental search for strong localization in the context of past and present experiments. This leads to a presentation of the most direct method to date to show effects of strong localization via time resolved transmission measurements. These recent experiments are discussed in detail and we draw some conclusions on the nature of the localization transition. The paper ends with an outlook on possible future experiments.

Chapter 1 The Resolution Challenge in 3D Optical Microscopy

Abstract: Publisher Summary This chapter discusses the theoretical principles of 3D microscopy with the widespread realizations of 3D microscopy.Based on the paraxial diffraction equations, it has been shown that conventional microscopes, when dealing with 3D fluorescent samples, provide sets of 2D images. These images of the different transverse sections of the 3D object contain, in addition to the sharp image of the in focus section, the blurred images of the rest of the specimen. The paraxial formalism has been generalized in a very simple way to a non-paraxial context, showing that the equations that govern non-paraxial imaging are similar to those that govern paraxial imaging. The only difference is the integral that provides the 3D PSF. Therefore, all the background acquired in many decades of study concerning paraxial imaging can easily be transferred to the non-paraxial regime.

Invisibility Cloaking by Coordinate Transformation

Abstract: Recently, the covariance property of the Maxwell equations under a coordinate transformation has been exploited for controlling the flow of electromagnetic waves in an unprecedented manner. Together with the development of electromagnetic metamaterial technologies, realization of perfect invisibility cloaks is no longer an intangible dream. Here we review both theoretical and experimental efforts to realize such invisibility cloaks. Their perspectives and limitations are also discussed.

Chapter 3 Photorefractive Solitons and Their Underlying Nonlocal Physics

Abstract: Publisher Summary Photorefractive solitons are the arena for a vast and innovative effort in nonlinear optics and nonlinear science as a whole. The chapter focuses on those aspects of the photorefractive soliton-supporting nonlinearity that are associated to the underlying physical mechanism, a light-driven charge migration in a full three-dimensional time-dependent setting. This migration process introduces nonlocality in both space and time, a feature that has a prevailing importance in many observed phenomena, starting from the observation of round 2D solitons. This nonlocality is discussed as the basis for the understanding of many of the peculiarities of the observed self-trapping and to render explicit the great potential that the direct coupling of an optical wave to an intrinsically nonlocal charge migration mechanism affords. Even though the charge migration process is not directly observed in experiments that detect the optical beam intensity, yet this hidden nonlocality is at the very heart of photorefractive self-trapping.

Chapter 4 Stimulated Scattering Effects of Intense Coherent Light

Abstract: Publisher Summary This chapter discusses the development and progress of stimulated scattering studies over the past four to five decades. The chapter focuses on the principles (mechanisms or models), basic experimental features, and technical applications of various stimulated scattering effects and related processes. Stimulated scattering is a very broad research subject. The key issues of the impulsive stimulated (Brillouin, Raman, and thermal) scattering studies are focused on the dynamic responses of short (or ultrashort) laser pulse-induced phonon fields. In a similar manner, studies of stimulated scattering in plasmas are mainly aimed at exploring opto-physical properties of the plasma medium. Other stimulated scattering-related issues, such as the CARS effect is a Raman-enhanced four wave frequency-mixing (FWFM) process, which requires phase-matching condition and can only occur in the forward direction.

Signal and Quantum Noise in Optical Communications and Cryptography

Abstract: Fundamental quantum noise manifestations in optical amplification, optical direct detection and coherent detection systems are presented from the physics and information theory basics to their system limitation or impairments. Application to optical communications and quantum cryptography will be discussed in relation to classical technical system impairments.

Chapter 6 Quantum Feed-Forward Control of Light

Abstract: Publisher Summary Quantum electro-optics feed-forward have made a major impact on the field of quantum information processing. Feed-forward has enabled the implementation of quantum teleportation—a universal squeezing operation—and a computational SUM gate. In addition, it is foreseen that it would enable the development of quantum error correction (QEC)-coding protocols and one-way quantum computation. Feed-forward control is a very important part of future quantum informational systems.