Reconfigurable Nanophotonic Cavities with Nonvolatile Response

 This is the author accepted manuscript. The final version is available from American Chemical Society via the DOI in this recordThe use of phase-change materials on waveguide photonics is presently being purported for a range of applications from on-chip photonic data storage to new computing paradigms. Photonic integrated circuits in combination with phase-change materials provide on-chip control handles, featuring nonvolatility and operation speeds down to the nano- and picosecond regime. Besides ultrafast control, efficient operation of nonvolatile elements is crucial and requires compact photonic designs. Here we embed phase-change materials in photonic crystal cavities to realize tunable nanophotonic devices which can be reconfigured on demand. The devices exploit strong light matter interactions between the resonant modes of the cavity and the evanescently coupled phase-change material cell. This results in an increased transmission contrast and a power reduction of 520% over conventional phase-change nanophotonic devices when reversibly switched with optical pulses. Such designs can thus open up new areas of reconfigurable nanophotonics without sacrificing the speeds or functionality for applications in optical memory cells, optical switches, and tunable wavelength filters.Engineering and Physical Sciences Research Council (EPSRC)European Research CouncilEuropean Union Horizon 202

On the Equation of State of Nuclear Matter in 158A GeV Pb+Pb Collisions

Within a hydrodynamical approach we investigate the sensitivity of single inclusive momentum spectra of hadrons in 158A GeV Pb+Pb collisions to three different equations of state of nuclear matter. Two of the equations of state are based on lattice QCD results and include a phase transition to a quark-gluon plasma. The third equation of state has been extracted from the microscopic transport code RQMD under the assumption of complete local thermalization. All three equations of state provide reasonable fits to data taken by the NA44 and NA49 Collaborations. The initial conditions before the evolution of the fireballs and the space-time evolution pictures differ dramatically for the three equations of state when the same freeze-out temperature is used in all calculations. However, the softest of the equations of state results in transverse mass spectra that are too steep in the central rapidity region. We conclude that the transverse particle momenta are determined by the effective softness of the equation of state during the fireball expansion.Comment: 4 pages, including 4 figures and 2 tables. For a PostScript file of the manuscript, you can also goto http://t2.lanl.gov/schlei/eprint.htm

Thermal photons as a measure for the rapidity dependence of the temperature

The rapidity distribution of thermal photons produced in Pb+Pb collisions at CERN-SPS energies is calculated within scaling and three-fluid hydrodynamics. It is shown that these scenarios lead to very different rapidity spectra. A measurement of the rapidity dependence of photon radiation can give cleaner insight into the reaction dynamics than pion spectra, especially into the rapidity dependence of the temperature.Comment: 3 Figure

Microscopic study of freeze-out in relativistic heavy ion collisions at SPS energies

The freeze-out conditions in the light (S+S) and heavy (Pb+Pb) colliding systems of heavy nuclei at 160 AGeV/$c$ are analyzed within the microscopic Quark Gluon String Model (QGSM). We found that even for the most heavy systems particle emission takes place from the whole space-time domain available for the system evolution, but not from the thin ''freeze-out hypersurface", adopted in fluid dynamical models. Pions are continuously emitted from the whole volume of the reaction and reflect the main trends of the system evolution. Nucleons in Pb+Pb collisions initially come from the surface region. For both systems there is a separation of the elastic and inelastic freeze-out. The mesons with large transverse momenta, $p_t$, are predominantly produced at the early stages of the reaction. The low $p_t$-component is populated by mesons coming mainly from the decay of resonances. This explains naturally the decreasing source sizes with increasing $p_t$, observed in HBT interferometry. Comparison with S+S and Au+Au systems at 11.6 AGeV/$c$ is also presented.Comment: REVTEX, 26 pages incl. 9 figures and 2 tables, to be published in the Physical Review

Reconfigurable nanophotonic cavities with nonvolatile response

The use of phase-change materials on waveguide photonics is presently being purported for a range of applications from on-chip photonic data storage to new computing paradigms. Photonic integrated circuits in combination with phase-change materials provide on-chip control handles, featuring nonvolatility and operation speeds down to the nano- and picosecond regime. Besides ultrafast control, efficient operation of nonvolatile elements is crucial and requires compact photonic designs. Here we embed phase-change materials in photonic crystal cavities to realize tunable nanophotonic devices which can be reconfigured on demand. The devices exploit strong light matter interactions between the resonant modes of the cavity and the evanescently coupled phase-change material cell. This results in an increased transmission contrast and a power reduction of 520% over conventional phase-change nanophotonic devices when reversibly switched with optical pulses. Such designs can thus open up new areas of reconfigurable nanophotonics without sacrificing the speeds or functionality for applications in optical memory cells, optical switches, and tunable wavelength filters

Reconfigurable nanophotonic cavities with nonvolatile response

The use of phase-change materials on waveguide photonics is presently being purported for a range of applications from on-chip photonic data storage to new computing paradigms. Photonic integrated circuits in combination with phase-change materials provide on-chip control handles, featuring nonvolatility and operation speeds down to the nano- and picosecond regime. Besides ultrafast control, efficient operation of nonvolatile elements is crucial and requires compact photonic designs. Here we embed phase-change materials in photonic crystal cavities to realize tunable nanophotonic devices which can be reconfigured on demand. The devices exploit strong light matter interactions between the resonant modes of the cavity and the evanescently coupled phase-change material cell. This results in an increased transmission contrast and a power reduction of 520% over conventional phase-change nanophotonic devices when reversibly switched with optical pulses. Such designs can thus open up new areas of reconfigurable nanophotonics without sacrificing the speeds or functionality for applications in optical memory cells, optical switches, and tunable wavelength filters