Carmel Rotschild

Two-dimensional multipole solitons in nonlocal nonlinear media

We present the experimental observation of scalar multipole solitons in highly nonlocal nonlinear media, including dipole, tripole, quadrupole, and necklace-type solitons, organized as arrays of out-of-phase bright spots. These complex solitons are metastable, but with a large parameters range where the instability is weak, permitting their experimental observation.

Dye alignment in luminescent solar concentrators: I. Vertical alignment for improved waveguide coupling

Luminescent solar concentrators (LSCs) use dye molecules embedded in a flat-plate waveguide to absorb solar radiation. Ideally, the dyes re-emit the absorbed light into waveguide modes that are coupled to solar cells. But some photons are always lost, re-emitted through the face of the LSC and coupled out of the waveguide. In this work, we improve the fundamental efficiency limit of an LSC by controlling the orientation of dye molecules using a liquid crystalline host. First, we present a theoretical model for the waveguide trapping efficiency as a function of dipole orientation. Next, we demonstrate an increase in the trapping efficiency from 66% for LSCs with no dye alignment to 81% for a LSC with vertical dye alignment. Finally, we show that the enhanced trapping efficiency is preserved for geometric gains up to 30, and demonstrate that an external diffuser can alleviate weak absorption in LSCs with vertically-aligned dyes.

Boundary force effects exerted on solitons in highly nonlinear media.

We study the effects caused by remote boundaries on soliton dynamics in nonlinear media with a large range of nonlocality, and demonstrate theoretically and experimentally how asymmetric boundary forces can lead to soliton steering and oscillation in predetermined trajectories.

Adjustable spiral phase plate

A spiral phase retarder phi(r, theta) = mtheta has been constructed with use of a deformed cracked plexiglass plate. By changing the degree of deformation, the retarder can be adjusted for use at any wavelength, and the value of the phase step 2pim at theta = 2pi can be chosen.

Soliton dynamics and self-induced transparency in nonlinear nanosuspensions

We study spatial soliton dynamics in nano-particle suspensions. Starting from the Nernst-Planck and Smoluchowski equations, we demonstrate that in these systems the underlying nonlinearities as well as the nonlinear Rayleigh losses depend exponentially on optical intensity. Two different nonlinear regimes are identified depending on the refractive index contrast of the nanoparticles involved and the interesting prospect of self-induced transparency is demonstrated. Soliton stability is systematically analyzed for both 1D and 2D configurations and their propagation dynamics in the presence of Rayleigh losses is examined. The possibility of synthesizing artificial nonlinearities using mixtures of nanosuspensions is also considered.

Dye alignment in luminescent solar concentrators: II. Horizontal alignment for energy harvesting in linear polarizers

We describe Linearly Polarized Luminescent Solar Concentrators (LP-LSCs) to replace conventional, purely absorptive, linear polarizers in energy harvesting applications. As a proof of concept, we align 3-(2-Benzothiazolyl)-N,N-diethylumbelliferylamine (Coumarin 6) and 4- dicyanomethyl-6-dimethylaminostiryl-4H-pyran (DCM) dye molecules linearly in the plane of the substrate using a polymerizable liquid crystal host. We show that up to 38% of the photons polarized on the long axis of the dye molecules can be coupled to the edge of the device for an LP-LSC based on Coumarin 6 with an order parameter of 0.52.

Roadmap on optical energy conversion

For decades, progress in the field of optical (including solar) energy conversion was dominated by advances in the conventional concentrating optics and materials design. In recent years, however, conceptual and technological breakthroughs in the fields of nanophotonics and plasmonics combined with a better understanding of the thermodynamics of the photon energy-conversion processes reshaped the landscape of energy-conversion schemes and devices. Nanostructured devices and materials that make use of size quantization effects to manipulate photon density of states offer a way to overcome the conventional light absorption limits. Novel optical spectrum splitting and photon-recycling schemes reduce the entropy production in the optical energy-conversion platforms and boost their efficiencies. Optical design concepts are rapidly expanding into the infrared energy band, offering new approaches to harvest waste heat, to reduce the thermal emission losses, and to achieve noncontact radiative cooling of solar cells as well as of optical and electronic circuitries. Light–matter interaction enabled by nanophotonics and plasmonics underlie the performance of the third- and fourth-generation energy-conversion devices, including up- and down-conversion of photon energy, near-field radiative energy transfer, and hot electron generation and harvesting. Finally, the increased market penetration of alternative solar energy-conversion technologies amplifies the role of cost-driven and environmental considerations. This roadmap on optical energy conversion provides a snapshot of the state of the art in optical energy conversion, remaining challenges, and most promising approaches to address these challenges. Leading experts authored 19 focused short sections of the roadmap where they share their vision on a specific aspect of this burgeoning research field. The roadmap opens up with a tutorial section, which introduces major concepts and terminology. It is our hope that the roadmap will serve as an important resource for the scientific community, new generations of researchers, funding agencies, industry experts, and investors.

Periodic solitons in nonlocal nonlinear media

We identify periodic solitons in nonlocal nonlinear media: multi-hump soliton solutions propagating in a fully periodic fashion. We also demonstrate recurrences and breathers whose evolution is statistically periodic and discuss why some systems support periodic solitons while others do not.

Computer-generated real-time digital holography: first time use in clinical medical imaging

AIMS Assessment of the feasibility of creating real-time interactive 3D digital holograms in a standard catheterization laboratory. 3D medical images are typically displayed and interacted with on 2D screens limiting their usefulness. A digital computer-generated real-time holographic display of patients 3D data could provide a spatially accurate image with all the depth cues and afford interaction within the image. METHODS AND RESULTS We performed a feasibility study of creating real-time interactive 3D digital holograms with a purpose-built prototype using intraprocedural data from 3D rotational angiography and live 3D transesophageal echocardiography. The primary objective was to demonstrate that all the anatomical landmarks identified on standard imaging can be similarly identified using dynamic and static holographic images. The secondary objective was to demonstrate the usability of interactions with the image. Parameters were assessed by a rating scale. Eight patients were enrolled of whom five underwent transcatheter ASD closure using 3DTEE and three patients were evaluated by 3D rotational angiography. In all cases dynamic real-time and static 3D holograms were created in standard cath lab conditions. Four individual observers identified all anatomical landmarks on the holographic display independently from the 2D display. Interactions with the hologram including marking, cropping and rotation were performed. There were no adverse events. CONCLUSIONS This study demonstrates, for the first time, the feasibility of generating high quality, clinically relevant, 3D real-time colour dynamic holograms in a standard clinical setting with real patient volumetric data. The impact of computer-generated holography needs to be evaluated in controlled clinical trials.

Optical beam instabilities in nonlinear nanosuspensions

We investigate the modulation instability of plane waves and the transverse instabilities of soliton stripe beams propagating in nonlinear nanosuspensions. We show that in these systems the process of modulational instability depends on the input beam conditions. On the other hand, the transverse instability of soliton stripes can exhibit new features as a result of 1D collapse caused by the exponential nonlinearity.