A. Aiello

Role of beam propagation in Goos-Hänchen and Imbert-Fedorov shifts.

We derive the polarization-dependent displacements parallel and perpendicular to the plane of incidence for a Gaussian light beam reflected from a planar interface, taking into account the propagation of the beam. Using a classical-optics formalism we show that beam propagation may greatly affect both Goos-Hänchen and Imbert-Fedorov shifts when the incident beam is focused.

Observation of Goos-Hänchen shifts in metallic reflection

We report the first observation of the Goos-Hänchen shift of a light beam incident on a bare metal surface. This phenomenon is particularly interesting because the Goos-Hänchen shift for p polarized light in metals is negative and much bigger than the positive shift for s polarized light. The experimental result for the measured shifts as a function of the angle of incidence is in excellent agreement with theoretical predictions. In an energy-flux interpretation, our measurement shows the existence of a backward energy flow at the bare metal surface when this is excited by a p polarized beam of light.

Loss-induced transition of the Goos-Hänchen effect for metals and dielectrics

We report a unifying approach to the Goos-Hänchen (GH) shifts on external optical reflection for metals and dielectrics in particular for the case of high losses, that is for a large imaginary part of the dielectric constant. In this regime metals and dielectrics have a similar GH shift which is in contrast to the low-loss regime where the metallic and dielectric forms of the GH shift are very different. When going from the low-loss to the high-loss regime we find that metals show a much more prominent transition; we present a condition on the dielectric constant which characterizes this transition. We illustrate our theoretical analysis with a realistic example of seven lossy materials.

Intrinsic entanglement degradation by multimode detection

Relations between photon scattering, entanglement, and multimode detection are investigated. We first establish a general framework in which one- and two-photon elastic scattering processes can be discussed; then, we focus on the study of the intrinsic entanglement degradation caused by a multimode detection. We show that any multimode scattered state cannot maximally violate the Bell-Clauser-Horne-Shimony-Holt inequality because of the momentum spread. The results presented here have general validity and can be applied to both deterministic and random scattering processes.

Observing nonspecular reflection of a light beam

The Law of Reflection of a light ray incident upon a mirror (θin = θout) was first formulated by Euclid around 300 BC in his book Catoptrics; it has been a tenet of geometrical optics ever since [1]. However, it has been discussed since the 1970s, that the Law of Reflection does not necessarily hold for a physical light beam, when this is regarded as the implementation of a ray [2–5]. The violation is due to a diffractive correction to geometrical optics; it may occur for oblique incidence on any mirror provided that its reflectivity is less than 100%. We present here the first experimental demonstration of this effect in the optical domain; it may affect all kinds of optical angular metrology, e.g. in Michelson interferometers and in cantilever-based surface probe microscopies as AFM.

Observing Angular Deviations in the Specular Refl ection of a Light Beam

Simple diffraction does not establish the limits on lateral resolution. We can use our new knowledge of light propagation to develop ultrasensitive instruments.

Observing Nonspecular Reflection of a Light Beam

We present here the first experimental demonstration of angularly nonspecular reflection of a light beam by a planar mirror; it occurs due to a diffractive correction if the mirror reflectivity is below 100%.

Angular dimensionality of two-photon entanglement

We pass twin-photons through rotatable angular phase plates, and detect entanglement that has a continuously variable angular dimensionality D. Experimentally, D was varied from 2 to 6 and values up to 50 are practically feasible.

Goos-Hänchen Shift on Flat and Not-So-Flat Metal Surfaces

We report the first observation of the Goos-Hanchen shift in metallic reflection. The shift is found to be insensitive to surface flatness but it depends on the microscopic roughness of the metal surface.

Quantum Entanglement of Singular Photons

We manipulate the azimuthal degrees of freedom of twin photons by rotating singular quantum projectors in signal and idler beams of a SPDC set-up. This allows generation of high-dimensional entangled two photon states.