We report on a high-intensity source of polarization-entangled photon pairs with high momentum definition. Type-II noncollinear phase matching in parametric down conversion produces true entanglement: No part of the wave function must be discarded, in contrast to previous schemes. With two-photon fringe visibilities in excess of 97%, we demonstrated a violation of Bell's inequality by over 100 standard deviations in less than 5 min. The new source allowed ready preparation of all four of the EPR-Bell states.

http://people.bu.edu/alexserg/Entangled.pdf

New high-intensity source of polarization-entangled photon pairs.

Over the last decade there have been spectacular developments in ultrafast laser technology, due to the introduction of solid state active materials and of new mode-locking and amplification techniques. These advances, together with the discovery of new nonlinear optical crystals, have fostered the introduction of ultrafast optical parametric amplifiers as a practical source of femtosecond pulses tunable across the visible and infrared spectral ranges. This article summarizes the recent progress in the development of ultrafast optical parametric amplifiers, giving the basic design principles for different frequency ranges and in addition presenting some advanced designs for the generation of ultrabroadband, few-optical-cycle pulses. Finally, we also briefly discuss the possibility of applying parametric amplification schemes to large-scale, petawatt-level systems.

Ultrafast optical parametric amplifiers

Singular optics is a branch of modern physical optics that involves a wide class of effects associated with the phase singularities in wave fields and with the topology of wave fronts. Optical singularities (optical vortices) exhibit some fundamental features absent in the "usual" fields with smooth wave fronts. Namely, optical vortices possess orbital angular momentum, topological charge for helical wave front of beams with well-defined direction of propagation. As a result, an interesting spatial evolution can be generated such as optical vortices "nucleation" and "annihilation" by pairs with participation of phase saddles, often called "optical chemistry." To study the structure of the circular edge dislocation, an isolated dark (zero-amplitude) ring is created within a light beam, with an analytical description of the field. A screw wave-front dislocation has a feature that the spatial structure of the wave front has the form of a helicoid around the dislocation axis. The chapter also describes reflection, refraction, interference and diffraction of OVs. Both frequency up- and down-conversion processes possess essential peculiarities for light beams with OVs. The chapter discusses the topology of wave fronts and vortex trajectories. Gouy phase shift in singular optics is also described in the chapter.

Chapter 4 - Singular optics

Towards quantum superpositions of a mirror

The prospects for ultrashort pulse duration and ultrahigh intensity using optical parametric chirped pulse amplifiers

This text provides a complete description of the properties and applications of all non-linear crystals reported in the literature up to the beginning of 1990. It also includes the most important equations for calculating parameters of non-linear frequency converters. This textbook on nonlinear optics and laser physics is intended for researchers, engineers and postgraduate students.

Handbook of nonlinear optical crystals

This chapter contains the main reference material, namely, optical and nonlinear optical properties of 77 crystals which are used in applied nonlinear optics for frequency conversion of laser light. All nonlinear optical crystals described in this chapter are divided into four groups: basic, frequently used, other inorganic, and other organic. The properties of crystalline quartz which is not phase-matchable but nevertheless is often used as a standard in the d-tensor coefficients’ measurements are given in a separate section. Inside every group of crystals an ordering of crystals according to the wavelength of the short-wave absorption edge was done.

Properties of Nonlinear Optical Crystals

This chapter introduces the main concepts of the physics of nonlinear optical processes: three-wave interactions, phase matching and phase-matching angle, role of phase mismatch for the interaction of quasi-plane waves, group-velocity mismatch and interaction of ultrashort light pulses, optics of uniaxial and biaxial crystals, crystal symmetry and effective nonlinearity, “walk-off” angle, phase-matching bandwidths (angular, temperature, spectral), thermal effects, and so on. It presents the main material required for calculating of phase-matching angles and for an assessment (as a rule, in approximation of quasi-plane light waves) of frequency conversion efficiency in the case of generation of optical harmonics and combination (sum and difference) frequencies, and optical parametric oscillation in nonlinear optical crystals. For convenience, the so-called “effective lengths” are introduced for the corresponding processes: by comparing the nonlinear crystal’s length with the effective length of the corresponding process, we may conclude whether this process must be taken into account for the calculation of the conversion efficiency or not. The chapter contains many tables with the equations for calculating phase-matching and “walk-off” angles, bandwidths, effective nonlinearity and conversion efficiency.

Optics of Nonlinear Crystals

This chapter contains the main reference material, namely, optical and nonlinear optical characteristics of the more than 50 crystals used most extensively in practice. Uniaxial and biaxial inorganic crystals as well as organic crystals are described. For each crystal, typical values of indices in the transparency range, dispersion relations (Sellmeier equations), linear and nonlinear (two-photon) absorption coefficients, symmetry group, nonzero components of the square susceptibility tensor, effective nonlinearities in the phase-matched direction, and optical breakdown thresholds for different laser pulse durations are given. The chapter contains many references. An index of the crystals is provided at the end of the handbook.

Nonlinear Optical Properties of Crystals

This chapter is devoted to applications of nonlinear crystals in nonlinear optical devices. It describes the generation of second and higher (up to sixth) optical harmonics of neodymium laser radiation, generation of optical harmonics of powerful wide-aperture neodymium glass laser radiation, generation of optical harmonics of other lasers (ruby, gas, semiconductor, and so on), sum-frequency generation, (including up-conversion of IR radiation to the visible range), difference-frequency generation, parametric light oscillation as a tool for generating tunable radiation, stimulated Raman scattering, and picosecond continuum generation. The chapter contains abundant tabular material on the parameters of converted laser radiation and many references.

Valentin G. Dmitriev

Papers

Handbook of nonlinear optical crystals

Properties of Nonlinear Optical Crystals

Optics of Nonlinear Crystals

Nonlinear Optical Properties of Crystals

Applications of Nonlinear Crystals