Three dimensional Light Bullets (3D-LBs) are the most symmetric solitary waves, being nonlinear optical
wavepackets propagating without diffraction nor dispersion. Since their theoretical prediction, 3D-LB's have
constituted a challenge in nonlinear science, due to the impossibility to avoid catastrophic collapse in conventional
homogeneous nonlinear media. We have recently observed stable 3D-LBs in media with periodically
modulated transverse refractive index profile. We found that higher order linear and nonlinear effects force the
3D-LBs to evolve along their propagation path and eventually decay. The evolution and decay mechanism entails
spatiotemporal effects, which under certain conditions, leads to superluminally propagating wavepackets.
Twisted light, or light with orbital angular momentum (OAM), plays an emerging role in both classical and quantum science, with important applications in areas as diverse as biophotonics, micromachines, spintronics, or quantum information. It offers fascinating opportunities for exploring new fundamental ideas in physics, as well as for being used as a tool for practical applications. One important point is to determine how to generate single photons, and two-photon states, with an appropriate OAM content. Here we describe the paraxial orbital angular momentum of entangled photon pairs generated by spontaneous parametric down-conversion (SPDC) in different non-collinear geometries. These geometries introduce a variety of new features. In particular, we find the OAM of entangled pairs generated in purely transverse-emitting configurations, where the entangled photons counter-propagate perpendicularly to the direction of propagation of the pump beam. The spatial walk-off of all interacting waves in the parametric process also determines the OAM content of the down-converted photons, and here its influence is also revealed.
The two-photon state generated by spontaneous parametric down-conversion (SPDC) exhibit spatial entanglement embedded in the corresponding mode function. The control of the spatial characteristics of the generated two-photon state is an issue of paramount importance. For example, the spatial entanglement of the two down converted photons forms the basis of quantum imaging, and entanglement in orbital angular momentum has opened a new scenario for implementing multidimensional Hilbert spaces. We put forward several techniques to engineer the spatial structure of entangled two-photon states generated in SPDC. The first strategy we consider for spatial control of the quantum state makes use of the direct manipulation of the pump beam. This technique makes feasible to prepare arbitrary engineered entangled states in any d-dimensional Hilbert space. The second strategy is based on the proper preparation of the down-converting crystal itself, namely quantum state manipulation by quasi-phase-matching (QPM) engineering. We use properly designed transversely varying QPM gratings in nonlinear crystals.
We elucidate the paraxial orbital angular momentum of entangled photon pairs generated by spontaneous parametric down-conversion (SPDC) in different non-collinear geometries. To date, most investigations addressed SPDC in nearly collinear phase-matching geometries, where the pump, the signal and idler photons propagate coaxially almost along the same direction. However, non-collinear geometries introduce a variety of new features. The OAM of the entangled photons strongly depend on the propagation direction of the photons. Here we show that locally paraxial measurements of the OAM conducted with entangled photons generated in non collinear geometries, they do not comply with the known selection rules for the spiral index of the pump, signal and idler mode functions (Mair et al., Nature 412, 313 (2001)). In particular, we find the orbital angular momentum of entangled pairs generated in purely transverse-emitting configurations, where the entangled photons counter-propagate perpendicularly to the direction of propagation of the pump beam. In transverse emitting configurations, the spatial shape of the down converted in one transverse dimensions strongly depends on the corresponding spatial shape of the input pump beam, while in the other transverse dimension, the shape is tailored by the longitudinal phase matching. The spatial walk-off of all interacting waves in the parametric process also determines the OAM content of the down-converted photons, and here its influence is also revealed.
We report theoretically the existence, classification and basic properties of families of stationary two-dimensional cnoidal-type waves in bulk Kerr-type saturable nonlinear media. This is the first known example of families of two-dimensional cnoidal-type wave solutions, which in addition are shown to exhibit richer features than their known one-dimensional counterparts. At low and high energy flows the cnoidal patterns are predicted to be robust enough to be observable experimentally.
We report the results of analytical and numerical studies of the reflection of N -soliton bound states at the interface formed by a Kerr nonlinear medium and a linear dielectric. A variety of effects are shown to occur, including bistability and soliton filtering, with applications to all-optical soliton switching concepts.
We show the dynamics of evolution of screw phase-dislocations existing in the wave front of Gaussian beam with nested multiple-charged vortices that propagate in quadratic nonlinear crystals under conditions for seeded second-harmonic generation. The number of existing vortices is shown to depend on the input light and material conditions, including the topological charge, width and intensity of the pump and seed signals, as well as on the propagation length inside the crystal.
In this paper we introduce the use of normalized parameters to study an electrooptically active
Y-Junction, by means of a five-layer model and the step approximation method. In a similar way
as it is done for three-layer and four-layer waveguides, we find a set of dimensionless parameters for
five-layer waveguides that allows the description of their waveguiding features.
In the present work we analyse the nonlinear, nonlocal response tensor describing optical second-harmonic processes
in centrosymmetric free-electron-like bulk metals with a flat surface. On the basis of the classical infinite barrier
(CIB)-model and the Boltzmann equation in the relaxation time approximation we present new analytic results for
the fully nonlocal nonlinear response tensor. Via numerical calculations the nonlinear, fully nonlocal response tensor's
dependence on the fundamental frequency is discussed and compared with that of the near-local (hydrodynamic)
response tensor. Finally, the significance of the contribution to the nonlinear, nonlocal optical response stemming
for single-particle excitations, i.e. Landau interactions, is considered.