176 research outputs found
A review of anomalous resonance, its associated cloaking, and superlensing
We review a selected history of anomalous resonance, cloaking due to
anomalous resonance, cloaking due to complementary media, and superlensing.Comment: 15 pages and 1 figur
Anisotropic focusing characteristics of micro-domain structures within crystalline Sr<sub>0.61</sub>Ba<sub>0.39</sub>Nb<sub>2</sub>O<sub>6</sub> : the crystal ball
We report the anisotropic focusing characteristics of a spherically configured region of micro-domains that have been induced within a cubic shaped crystal of Ce:doped Sr0.61Ba0.39Nb2O6. The internal spherical structure focuses extraordinary polarised light, but not ordinary polarised. The spherical region, which is easily observed via scattering, is formed as the crystal cools down, after a repoling cycle through the Curie temperature, with an applied field. Analytic modelling of the thermal gradients that exist within the crystal during cooling reveals a small (< 1°) temperature difference between the central and outside regions. The similarity in shape between these temperature profiles and the observed scattering region suggests a possible mechanism for the growth of this spherical micro-domained structure
Temperature sensitivity of repoling in strontium barium niobate near to the glassy transition
We report the observation of an enhanced temperature sensitivity for transient repoling near to the domain freezing temperature in ferroelectric strontium barium niobate. This work has important consequences for the use of optical fields to control domain patterns in such materials. We model the repoling characteristics of the material using a Vogel-Fulcher type response and present results showing the degree of repoling as a function of field and temperature, for short duration repoling times
Phase conjugate fluorozirconate fibre laser operating at 800nm
We report phase-conjugate feedback into a fluorozirconate optical fiber amplifier at infrared wavelengths. By using a semiconductor laser diode at 807 nm, a grating is established in photorefractive BaTiO3 that, in the ring configuration, provides feedback into the amplifier necessary for laser action. Once written, the grating is self-sustaining, and lasing is observed even after the laser diode is removed
Selective radiolabelling with 68Ga under mild conditions: a route towards a porphyrin PET/PDT theranostic agent
A theranostic conjugate for use as a positron emission tomography (PET) radiotracer and as a photosensitiser for photodynamic therapy (PDT) has been synthesised. A water-soluble porphyrin was coupled with the bifunctional chelate, H4Dpaa.ga. This conjugate is capable of rapid68Ga complexation under physiological conditions; with 93% and 80% radiochemical yields achieved, at pH 4.5 and pH 7.4 respectively, in 15 min at 25 °C. Photocytotoxicity was evaluated on HT-29 cells and showed the conjugate was capable of >50% cell death at 50 ΌM upon irradiation with light, while causing minimal toxicity in the absence of light (>95% cell survival)
Opaque perfect lenses
The response of the ``perfect lens'', consisting of a slab of lossless
material of thickness with at one frequency is
investigated. It is shown that as time progresses the lens becomes increasingly
opaque to any physical TM line dipole source located a distance from
the lens and which has been turned on at time . Here a physical source is
defined as one which supplies a bounded amount of energy per unit time. In fact
the lens cloaks the source so that it is not visible from behind the lens
either. For sources which are turned on exponentially slowly there is an exact
correspondence between the response of the perfect lens in the long time
constant limit and the response of lossy lenses in the low loss limit. Contrary
to the usual picture where the field intensity has a minimum at the front
interface we find that the field diverges to infinity there in the long time
constant limit.Comment: The 7th International Conference on the Electrical transport and
Optical Properties of Inhomogenous Media (ETOPIM7
Solutions in folded geometries and associated cloaking due to anomalous resonance
Solutions for the fields in a coated cylinder where the core radius is bigger than the shell radius are seemingly unphysical, but can be given a physical meaning if one transforms to an equivalent problem by unfolding the geometry. In particular, the unfolded material can act as an impedance matched hyperlens, and as the loss in the lens goes to zero finite collections of polarizable line dipoles lying within a critical region surrounding the hyperlens are shown to be cloaked having vanishingly small dipole moments. This cloaking, which occurs both in the folded geometry and the equivalent unfolded one, is due to anomalous resonance, where the collection of dipoles generates an anomalously resonant field, which acts back on the dipoles to essentially cancel the external fields acting on them
Synthesis of a porphyrin with histidine-like chelate: an efficient path towards molecular PDT/SPECT theranostics
© The Royal Society of Chemistry 2020. The goal of âpersonalisedâ medicine has seen a growing interest in the development of theranostic agents. Bifunctional, and targeted-trifunctional, theranostic water-soluble porphyrins with a histidine-like chelating group have been synthesisedviacopper-catalysed azide-alkyne cycloaddition (CuAAC) âclickâ chemistry in high yield and purity. They are capable of photodynamic treatment and [99mTc(CO)3]+complexation for single-photon emission computed tomography (SPECT) imaging, with a radiochemical yield of >95%. The toxicity and phototoxicity were evaluated on HT-29 cells, DU145, and DU145-PSMA cell lines, with the targeted theranostic showing more potent phototoxicity towards DU145-PSMA expressing cells
Fast electron transport patterns in intense laser-irradiated solids diagnosed by modeling measured multi-MeV proton beams
The measured spatial-intensity distribution of the beam of protons accelerated from the rear side of a solid target irradiated by an intense (>10 Wcm) laser pulse provides a diagnostic of the two-dimensional fast electron density profile at the target rear surface and thus the fast electron beam transport pattern within the target. An analytical model is developed, accounting for rear-surface fast electron sheath dynamics, ionization and projection of the resulting beam of protons. The sensitivity of the spatial-intensity distribution of the proton beam to the fast electron density distribution is investigated. An annular fast electron beam transport pattern with filamentary structure is inferred for the case of a thick diamond target irradiated at a peak laser intensity of 6 Ă 10 Wcm
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