Multi-Photon Interference and Temporal Distinguishability of Photons

A number of recent interference experiments involving multiple photons are reviewed. These experiments include generalized photon bunching effects, generalized Hong-Ou-Mandel interference effects and multi-photon interferometry for demonstrations of multi-photon de Broglie wavelength. The multi-photon states used in these experiments are from two pairs of photons in parametric down-conversion. We find that the size of the interference effect in these experiments, characterized by the visibility of interference pattern, is governed by the degree of distinguishability among different pairs of photons. Based on this discovery, we generalize the concept of multi-photon temporal distinguishability and relate it to a number of multi-photon interference effects. Finally, we make an attempt to interpret the coherence theory by the multi-photon interference via the concept of temporal distinguishability of photons.Comment: fixed figures 4,5,

Spin correlated interferometry for polarized and unpolarized photons on a beam splitter

Spin interferometry of the 4th order for independent polarized as well as unpolarized photons arriving simultaneously at a beam splitter and exhibiting spin correlation while leaving it, is formulated and discussed in the quantum approach. Beam splitter is recognized as a source of genuine singlet photon states. Also, typical nonclassical beating between photons taking part in the interference of the 4th order is given a polarization dependent explanation.Comment: RevTeX, 19 pages, 1 ps figure, author web page at http://m3k.grad.hr/pavici

Enhanced conversion efficiency for harmonic generation with double resonance

Conversion efficiency for cw harmonic generation is calculated for the situation in which both fundamental and harmonic waves are resonant. Compared with the situation of a singly resonant cavity at the fundamental, the doubly resonant geometry can lead to an increase of the effective nonlinear coefficient. High conversion efficiency can thus be achieved with nonlinear crystals of relatively low nonlinear coefficient. and with modest pump power for the fundamental input

Projection Measurement of the Maximally Entangled N-Photon State for a Demonstration of N-Photon de Broglie Wavelength

We construct a projection measurement process for the maximally entangled N-photon state (the NOON-state) with only linear optical elements and photodetectors. This measurement process will give null result for any N-photon state that is orthogonal to the NOON state. We examine the projection process in more detail for N=4 by applying it to a four-photon state from type-II parametric down-conversion. This demonstrates an orthogonal projection measurement with a null result. This null result corresponds to a dip in a generalized Hong-Ou-Mandel interferometer for four photons. We find that the depth of the dip in this arrangement can be used to distinguish a genuine entangled four-photon state from two separate pairs of photons. We next apply the NOON state projection measurement to a four-photon superposition state from two perpendicularly oriented type-I parametric down-conversion processes. A successful NOON state projection is demonstrated with the appearance of the four-photon de Broglie wavelength in the interference fringe pattern.Comment: 8 pages, 3 figures, new title, some content change, replaced Fig.

Reconfigurable photonic metamaterials drive by Coulomb, Lorentz and optical forces

Metamaterials offer a huge range of enhanced and novel functionalities that natural materials cannot provide. They promise applications in superresolution imaging, optical data storage, optical filters, polarization control, cloaking, fraud prevention and many more. However, their unique optical properties are often narrowband and usually fixed. Here we demonstrate how the mechanical rearrangement of metamaterial structures at the nanoscale provides a powerful platform for controlling metamaterial properties dynamically. Using thermal, electrical, magnetic and optical control signals we demonstrate large-range tuning, high-contrast switching and modulation of metamaterial optical properties at megahertz frequencies and beyond. Beyond the obvious benefit of adding tunability to known metamaterial functionalities, this unlocks many new opportunities in areas such as light modulation and highly nonlinear & bistable optical device