Quantum lithography by coherent control of classical light pulses

The smallest spot in optical lithography and microscopy is generally limited by diffraction. Quantum lithography, which utilizes interference between groups of N entangled photons, was recently proposed to beat the diffraction limit by a factor N. Here we propose a simple method to obtain N photons interference with classical pulses that excite a narrow multiphoton transition, thus shifting the "quantum weight" from the electromagnetic field to the lithographic material. We show how a practical complete lithographic scheme can be developed and demonstrate the underlying principles experimentally by two-photon interference in atomic Rubidium, to obtain focal spots that beat the diffraction limit by a factor of 2.Comment: 6 pages, 4 figures, Submitted to Opt. Expres

Nonlinear interactions with an ultrahigh flux of broadband entangled photons

We experimentally demonstrate sum-frequency generation (SFG) with entangled photon-pairs, generating as many as 40,000 SFG photons per second, visible even to the naked eye. The nonclassical nature of the interaction is exhibited by a linear intensity-dependence of the nonlinear process. The key element in our scheme is the generation of an ultrahigh flux of entangled photons while maintaining their nonclassical properties. This is made possible by generating the down-converted photons as broadband as possible, orders of magnitude wider than the pump. This approach is readily applicable for other nonlinear interactions, and may be applicable for various quantum-measurement tasks.Comment: 4 pages, 2 figures, Accepted to Phys. Rev. Let

Updated Semiempirical Cross Sections for Cosmic Rays Propagation

High precision cross sections estimates are crucial to help infer the source abundance of elements and isotopes that have large secondary components in the arriving cosmic-ray abundances, e.g., N, Na, Al and P. We propose here correction factors to further refine our recent semiempirical cross sections estimates. Factors for elements that are nearly purely secondary, e.g, B and F, are also proposed for improved propagation calculations. We also point to some inconsistencies in the measured cross sections. The nucleus-nucleus component, including scaling factors, as well as a non-nuclear contribution to the inelastic cross section therein are also discussed

Hanbury Brown and Twiss Correlations of Anderson Localized Waves

When light waves propagate through disordered photonic lattices, they can eventually become localized due to multiple scattering effects. Here we show experimentally that while the evolution and localization of the photon density distribution is similar in the two cases of diagonal and off-diagonal disorder, the density-density correlation carries a distinct signature of the type of disorder. We show that these differences reflect a symmetry in the spectrum and eigenmodes that exists in off-diagonally disordered lattices but is absent in lattices with diagonal disorder.Comment: 4 pages, 3 figures, comments welcom

A Comparison of Models of Cosmic-Ray Source Composition

Several models for the origin of cosmic rays have been proposed to explain the relative differences of cosmic-ray source abundances and the general abundances of elements and isotopes. One model, for example, assumes injection at normal stars like the sun, using FIP-modified coronal rather than photospheric abundances. Another with acceleration and breakup of grains by supernova shock waves has been popular with several authors. On the basis of the known abundances of few elements, we demonstrate how a critical evaluation of one model's merits against the others can be made

Cosmic-Ray Sources and Source Composition

Present data on cosmic-ray elemental and isotopic relative abundances are shown to be unable to distinguish between various models of cosmic-ray sources and their composition. For example, the model of freshly nucleosynthesized material from supernova explosions as the cosmic-ray source is unable to account for some measured, key cosmic-ray elemental abundances. This and two other models are evaluated here in light of recent isotopic and elemental measurements. It is shown that model-dependent preferential injection, acceleration, and reacceleration do not allow a clear distinction of one model against the others. Future measurements of critical elements and isotopes are suggested, which should afford us the ability to do that. We base our suggestions on measurements and a quantitative comparison between the predictions of the standard leaky-box model for the Galactic propagation of cosmic rays and one in which reacceleration is taken into account

Parametric Self-Oscillation via Resonantly Enhanced Multiwave Mixing

We demonstrate an efficient nonlinear process in which Stokes and anti-Stokes components are generated spontaneously in a Raman-like, near resonant media driven by low power counter-propagating fields. Oscillation of this kind does not require optical cavity and can be viewed as a spontaneous formation of atomic coherence grating

All-Optical Switching with Transverse Optical Patterns

We demonstrate an all-optical switch that operates at ultra-low-light levels and exhibits several features necessary for use in optical switching networks. An input switching beam, wavelength $\lambda$, with an energy density of $10^{-2}$ photons per optical cross section [$\sigma=\lambda^2/(2\pi)$] changes the orientation of a two-spot pattern generated via parametric instability in warm rubidium vapor. The instability is induced with less than 1 mW of total pump power and generates several $\mu$Ws of output light. The switch is cascadable: the device output is capable of driving multiple inputs, and exhibits transistor-like signal-level restoration with both saturated and intermediate response regimes. Additionally, the system requires an input power proportional to the inverse of the response time, which suggests thermal dissipation does not necessarily limit the practicality of optical logic devices