74 research outputs found
Spatial entanglement of twin quantum images
We show that spatial entanglement of two twin images obtained by parametric
down-conversion is complete, i.e. concerns both amplitude and phase. This is
realised through a homodyne detection of these images which allows for
measurement of the field quadrature components. EPR correlations are shown to
exist between symmetrical pixels of the two images. The best possible
correlation is obtained by adjusting the phase of the local oscillator field
(LO) in the area of maximal amplification. The results for quadrature
components hold unchanged even in absence of any input image i.e. for pure
parametric fluorescence. In this case they are not related to intensity and
phase fluctuations.Comment: 19 pages, 2 figure
Spatial entanglement of twin quantum images
We show that the spatial entanglement of two twin images obtained by parametric down conversion is complete, i.e., concerns both amplitude and phase. By considering a homodyne detection scheme, which allows comparison of field quadrature components of the two images pixel by pixel, Einstein-Podolsky Rosen correlations are shown to exist between symmetrical pixels of the two images. The best possible correlation is obtained by adjusting the phase profile of the local oscillator in the amplification area. The results for quadrature components hold even in the absence of any input image, i.e., for pure parametric fluorescence. In this case, they are not related to intensity and phase fluctuations
Differential Ghost Imaging
We present a new technique, differential ghost imaging (DGI), which dramatically enhances the signal-to-noise ratio (SNR) of imaging methods based on spatially correlated beams. DGI can measure the transmission function of an object in absolute units, with a SNR that can be orders of magnitude higher than the one achievable with the conventional ghost imaging (GI) analysis. This feature allows for the first time, to our knowledge, the imaging of weakly absorbing objects, which represents a breakthrough for GI applications. Theoretical analysis and experimental and numerical data assessing the performances of the technique are presented
Quantum structures in nonlinear optics and atomic physics : a background overview
A brief overview of quantum effects in spatial structures such as nonlinear optical patterns, chains of trapped ions and atoms in optical lattices is presented. Some of the main results of the contributions to this Focus Issue are also briefly described
Spatio-temporal dynamics in semiconductor microresonators with thermal effects.
In this paper we study the dynamics of the intracavity field, carriers and lattice temperature in externally driven semiconductor microcavities. The combination/competition of the different time-scales of the dynamical variables together with diffraction and carrier/thermal diffusions are responsible for new dynamical behaviors. We report here the occurrence of a spatio-temporal instability of the Hopf type giving rise to Regenerative Oscillations and travelling patterns and cavity solitons
Microresonator defects as sources of drifting cavity solitons
Cavity solitons (CS) are localized structures appearing as single intensity peaks in the homogeneous background of the field emitted by a nonlinear (micro)resonator. In real devices, their position is strongly influenced by the presence of defects in the device structure. In this Letter we show that the interplay between these defects and a phase gradient in the driving field induces the spontaneous formation of a regular sequence of CSs moving in the gradient direction. Hence, defects behave as a device built-in CS source, where the CS generation rate can be set by controlling the system parameters
Spatial patterns in optical parametric oscillators with spherical mirrors: classical and quantum effects: errata
We investigate the formation of transverse patterns in a doubly resonant degenerate optical parametric oscillator. Extending previous work, we treat the more realistic case of a spherical mirror cavity with a finite-sized input pump field. Using numerical simulations in real space, we determine the conditions on the cavity geometry, pump size and detunings for which pattern formation occurs; we find multistability of different types of optical patterns. Below threshold, we analyze the dependence of the quantum image on the width of the input field, in the near and in the far field
Self-generation of optical frequency comb in single section Quantum Dot Fabry-Perot lasers: a theoretical study
Optical Frequency Comb (OFC) generated by semiconductor lasers are currently
widely used in the extremely timely field of high capacity optical
interconnects and high precision spectroscopy. Very recently, several
experimental evidences of spontaneous OFC generation have been reported in
single section Quantum Dot (QD) lasers. Here we provide a physical
understanding of these self-organization phenomena by simulating the multi-mode
dynamics of a single section Fabry-Perot (FP) QD laser using a Time-Domain
Traveling-Wave (TDTW) model that properly accounts for coherent
radiation-matter interaction in the semiconductor active medium and includes
the carrier grating generated by the optical standing wave pattern in the laser
cavity. We show that the latter is the fundamental physical effect at the
origin of the multi-mode spectrum appearing just above threshold. A
self-mode-locking regime associated with the emission of OFC is achieved for
higher bias currents and ascribed to nonlinear phase sensitive effects as Four
Wave Mixing (FWM). Our results are in very good agreement with the experimental
ones
Soliton dynamics of ring quantum cascade lasers with injected signal
AbstractNonlinear interactions in many physical systems lead to symmetry breaking phenomena in which an initial spatially homogeneous stationary solution becomes modulated. Modulation instabilities have been widely studied since the 1960s in different branches of nonlinear physics. In optics, they may result in the formation of optical solitons, localized structures that maintain their shape as they propagate, which have been investigated in systems ranging from optical fibres to passive microresonators. Recently, a generalized version of the Lugiato–Lefever equation predicted their existence in ring quantum cascade lasers with an external driving field, a configuration that enables the bistability mechanism at the basis of the formation of optical solitons. Here, we consider this driven emitter and extensively study the structures emerging therein. The most promising regimes for localized structure formation are assessed by means of a linear stability analysis of the homogeneous stationary solution (or continuous-wave solution). In particular, we show the existence of phase solitons – chiral structures excited by phase jumps in the cavity – and cavity solitons. The latter can be deterministically excited by means of writing pulses and manipulated by the application of intensity gradients, making them promising as frequency combs (in the spectral domain) or reconfigurable bit sequences that can encode information inside the ring cavity
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