Light Field Modes Research Articles

Unraveling the Quantum Nature of Atomic Self-Ordering in a Ring Cavity.

Atomic self-ordering to a crystalline phase in optical resonators is a consequence of the intriguing nonlinear dynamics of strongly coupled atom motion and photons. Generally the resulting phase diagrams and atomic states can be largely understood on a mean-field level. However, close to the phase transition point, quantum fluctuations and atom-field entanglement play a key role and initiate the symmetry breaking. Here we propose a modified ring cavity geometry, in which the asymmetry imposed by a tilted pump beam reveals clear signatures of quantum dynamics even in a larger regime around the phase transition point. Quantum fluctuations become visible both in the dynamic and steady-state properties. Most strikingly we can identify a regime where a mean-field approximation predicts a runaway instability, while in the full quantum model the quantum fluctuations of the light field modes stabilize uniform atomic motion. The proposed geometry thus allows to unveil the "quantumness" of atomic self-ordering via experimentally directly accessible quantities.

Investigation of the dynamics of expansion of the near-surface light erosion plasma formed during the evaporation of a material by broadband high-brightness radiation

The dynamics of the vapor-plasma flows formed at impact of erosion type magnetoplasma compressor (MPC) discharge radiation on Ti, Al and PTFE targets with use of methods of a holographic interferometry and schlieren photos (Toepler’s scheme in the light field mode) is investigated. In the schlieren and interferogram photos, zones characteristic of the studied process of radiation interaction with matter are well visible: the gas-dynamic evaporation mode is realized (plasma piston mode), there is a shock wave in the gas, the contact boundary between the shock-compressed gas and the vapor plasma. The interferograms analysis indicates that the regime of developed evaporation is preceded by a regime of diffusion evaporation. On the interferograms above the targets at different distances from the radiation source (from the MPC), we observe 3 types of gas-dynamic perturbations: an acoustic wave, a simple wave (Riemann wave), and a shock wave. Qualitative and quantitative description of processes in these zones is discussed in the report. The effect of the radiation spectral composition (we use the method of gas spectral selection), the targets materials, and the degree of surface treatment on the evaporation is shown experimentally.

The Light Field Attachment: Turning a DSLR into a Light Field Camera Using a Low Budget Camera Ring.

We propose a concept for a lens attachment that turns a standard DSLR camera and lens into a light field camera. The attachment consists of eight low-resolution, low-quality side cameras arranged around the central high-quality SLR lens. Unlike most existing light field camera architectures, this design provides a high-quality 2D image mode, while simultaneously enabling a new high-quality light field mode with a large camera baseline but little added weight, cost, or bulk compared with the base DSLR camera. From an algorithmic point of view, the high-quality light field mode is made possible by a new light field super-resolution method that first improves the spatial resolution and image quality of the side cameras and then interpolates additional views as needed. At the heart of this process is a super-resolution method that we call iterative Patch- And Depth-based Synthesis (iPADS), which combines patch-based and depth-based synthesis in a novel fashion. Experimental results obtained for both real captured data and synthetic data confirm that our method achieves substantial improvements in super-resolution for side-view images as well as the high-quality and view-coherent rendering of dense and high-resolution light fields.

A Gradient Index Liquid Crystal Microlens Array for Light-Field Camera Applications

We have developed a microlens array (MLA) that utilizes liquid crystal (LC) for switching between light field and normal picturing modes in the camera application. The gradient index (GRIN) profile in an LC layer was obtained by applying the electric field distribution between a pair of molded-and-buried concave and planar electrodes. The concave array was formed by the imprinting method with ultraviolet curing resin. An indium tin oxide layer was deposited on the concave array to make the transparent electrode, which was then buried and flattened with the same resin. The transparency and flatness of the electrodes and resin keep the image quality high without applied voltage in the normal mode, and the electrode in the concave shape causes the LC layer to have a GRIN profile that acts as a MLA when voltage is applied in the light-field mode. The fabricated MLA showed suitable mode-switching operations by applying (for light-field mode) or not applying (for normal mode) a voltage of ±4 V.

Efficiency and fidelity of photon-echo quantum memory in an atomic system with longitudinal inhomogeneous broadening

We have performed a theoretical analysis of the photon-echo-based quantum memory realized recently in A. L. Alexander et al., Phys. Rev. Lett. 96, 043602 (2006) in the medium with linear correlation between atomic spatial coordinates and frequency detunings of the inhomogeneously broadened transition. A more general vision on the physical picture of temporal and spatial light-atoms dynamics has been obtained in the analytical solutions, taking into account the atomic phase relaxation, inhomogeneous broadening, and arbitrary parameters of the probe light pulses. We have evaluated preferable experimental conditions for the storage of incoming data light field modes where quantum memory efficiency and fidelity have been found. Physics of high efficiency in the forward geometry of the quantum memory and advantages for the realization of more universal long-lived storage on this basis are clarified.

Cavity QED with a Bose–Einstein condensate

Cavity quantum electrodynamics (cavity QED) describes the coherent interaction between matter and an electromagnetic field confined within a resonator structure, and is providing a useful platform for developing concepts in quantum information processing. By using high-quality resonators, a strong coupling regime can be reached experimentally in which atoms coherently exchange a photon with a single light-field mode many times before dissipation sets in. This has led to fundamental studies with both microwave and optical resonators. To meet the challenges posed by quantum state engineering and quantum information processing, recent experiments have focused on laser cooling and trapping of atoms inside an optical cavity. However, the tremendous degree of control over atomic gases achieved with Bose-Einstein condensation has so far not been used for cavity QED. Here we achieve the strong coupling of a Bose-Einstein condensate to the quantized field of an ultrahigh-finesse optical cavity and present a measurement of its eigenenergy spectrum. This is a conceptually new regime of cavity QED, in which all atoms occupy a single mode of a matter-wave field and couple identically to the light field, sharing a single excitation. This opens possibilities ranging from quantum communication to a wealth of new phenomena that can be expected in the many-body physics of quantum gases with cavity-mediated interactions.

Surface plasmon polaritons in metal stripes and wires.

Surface plasmon polaritons (SPPs) are collective electron oscillations coupled to a light field which are propagating along the interface of a metal and a dielectric. As a surface wave, SPP modes feature properties essentially different from light-field modes in all dielectric structures. These properties could allow the realization of novel photonic devices that overcome certain limitations of conventional devices. Specifically, the realization of two-dimensional optics and light-field transport in sub-wavelength SPP waveguides seems feasible. In this review we discuss recent experimental advances regarding SPP waveguides, i.e. laterally confined metal thin films that guide SPPs. Electron-beam lithography is applied to tailor these films with widths ranging from a few micrometres (stripes) to nanoscopic values (wires). We investigate SPP properties such as propagation length, mode field profile and reflection or scattering at interfaces. Various techniques for SPP excitation and detection are discussed.

The split-density model: a unified description of polarization and array dynamics for vertical-cavity surface-emitting lasers

A rate equation model describing the laser dynamics of general one or two dimensional vertical cavity surface emitting laser (vcsel) arrays is introduced. It is shown that the theory includes both the previous theory for edge emitting semiconductor laser arrays and the theory of polarization dynamics in single quantum well vcsels in a single unified description. The model is based on the physical assumption of separate carrier density pools individually coupled to different light field modes. These modes interact through the coherent light field dynamics derived from Maxwell's equations. The special case of two densities and two light field modes is solved and the implications for larger arrays are discussed. Our analytic results show that typical solutions of the split density model range from phase locking to chaos, depending on the magnitude of the coherent interaction. For weak coupling the stable supermode is always the mode of highest frequency. This indicates that anti-phase locking is the only stable phase locking possible in semiconductor laser arrays.