Session D2: Contributed Session II: Quantum Optics and Nanophotonics

Quantum Signal Transmission and Phenomenon of Superradiance

Electronic transport through one-dimensional periodic structures is investigated utilizing the method of effective non-Hermitian Hamiltonian based on the Feshbach projection formalism [1]. In an open system the internal states become resonances. At sufficiently strong coupling to the leads the resonances undergo a sharp redistribution of decay widths resulting in segregation of short-lived ``superradiant" states and long-lived ``trapped" states. The superradiant phase transition significantly enhances the transport through the structure [2,~3]. One of the advantages of the formalism is its flexibility which allows for a straightforward incorporation of extra elements (qubits), disorder and additional degrees of freedom, such as phonons. Numerical results of transport through different structures are presented. \begingroup \renewcommand{\section}[2]{} \begin{thebibliography}{1} \bibitem{Zelevinsky} V.~V.~Sokolov and V.~G.~Zelevinsky, Ann. Phys. {\bf 216}, 323 (1992). \bibitem{Tayebi1} Y.~S.~Greenberg, C.~Merrigan, A.~Tayebi, and V.~Zelevinsky, Eur. Phys. J. B {\bf 86}, 368 (2013). \bibitem{Tayebi2} A.~Tayebi, and V.~Zelevinsky, AIP Conf. Proc., {\bf 1619}, 162 (2014). \end{thebibliography} \endgroup   

Theoertical investigation of quantum waveform shaping for single-photon emitters

In this work, we investigate a new technique for quantum-compatible waveform shaping that goes beyond the time-lens limit. Under realistic experimental conditions, it is shown that it is possible to both temporally compress and shape optical waveforms in the nanosecond to hundreds of picoseconds range, which is generally difficult to achieve using standard dispersive pulse-shaping techniques. The results of our theoretical investigation indicate that it is possible not only to perform wavelength translation, but also to change the spectro-temporal shape of input waveforms in a coherent manner and lossless manner, as our approach involves phase operations only. We calculate both the necessary phase operations and show how they can be performed under realistic experimental conditions. Numerical simulations under these conditions indicate that the technique is well suited to the regime of operation of single photon emitters that are characterized by photon lifetimes that are too long for standard dispersive waveform shaping.   

Quantum Tunneling in Metal-Insulator-Metal Nanoantennas

The goal of this research is to experimentally examine the optical properties of nanometer-sized metal-insulator-metal (MIM) structures. A set of experiments are designed to measure the second and third-harmonic waves scattered from the nanostructured MIM antenna when illuminated with different lasers and, also, to quantify the current/voltage characteristics of carefully fabricated MIMs. The MIM sample geometry is designed so that there is a nanometer-sized gap between two metals that is filled with an insulator (dielectric) material. The prediction of higher-order optical harmonics generation related to the MIM geometry is predicated on the photon-assisted, electronic quantum tunneling process. The quantum tunneling process calculates a set of conductivities that is used in our numerical simulations to describe the electromagnetic properties of the MIM. The initial results from numerical simulations were compared to other numerically intensive methods available in the literature to validate them. For this research, we extend the validation process by performing more numerical simulations to compare with data from our optical experiments. Our research is guided by numerical calculations to find the optimal conditions for generating the optical harmonic waves.   

Silver nanoparticles as a potential solar absorber and the effect of UV-C irradiation during synthesis

This work reports the possibility of developing Silver nanoparticles implanted into a polymer as a solar absorber. The plasmonic nature of the silver nanoparticle allows for adjustments to be made in its UV-VIS-NIR absorbance spectrum. A combination of different sized/shaped particles could result in ideal absorption of the majority of the solar spectrum. Allotting this with the stability of a polymer leads to potential solids or solutions that could work as a solar absorber. Tests were also performed to determine whether or not UV-C irradiation during synthesis affects the characteristics of silver nanoparticles, in particular the absorbance. Successful synthesis of Silver nanoparticles in solid form or as colloidal particles in a solution by using a strong reducing agent was achieved, with stabilization of the particles in a polymer material. By controlling the reactivity of the reducing agent used in the synthesis process, we are able to significantly affect the plasma frequency of the particles. UV-C light irradiation during synthesis led to relatively higher absorbance levels in both the solids and the colloidal particles. Silver nanoparticles with different plasmon frequencies combined with the effect of UV-C irradiation during synthesis have potential for solar absorbing technology.   

Synthesis of nearly Monodispersed Nanocrystals via Colloidal Atomic Layer Deposition(c-ALD)

Due to the overwhelming demand, the need of miniaturization of the semiconductor devices is growing. Nanocrystals, with properties different from those of the corresponding bulk structures, can be building blocks for the next generation of technology. However, polydispersity in size and shape, less control over the nanocrystal stoichiometry, surface chemistry defects, poor crystallinity, etc., are some of the reasons that inhibit use of nanocrystals in a wide variety of applications. In our lab, we have demonstrated a general strategy to synthesize monodispersed quantum dots exhibiting a size dispersion below 5{\%}. So, this presentation will be about the underlying notions about the growth of high quality nearly monodispersed nanometer size crystallites, with emphasis on CdS.   

Improved synthesis of YAG nanophosphors for light emitting diodes

Ce-doped YAG (CeYAG) is an excellent phosphor for blue light emitting diodes (LED) with unique properties including strong absorption at the blue LED wavelength, broad-band yellow emission and high quantum efficiency. CeYAG phosphors synthesized by simple chemical methods would reduce cost and enhance performance. In this work, we synthesize YAG nanophosphors using the sol-gel method. It is obvious that the use of nano-phosphors instead of large grain-sized phosphors should reduce light scattering. YAG and CeYAG precursors were prepared using metal nitrates with various chemical agents and photo-irradiation and then converted to a gel and then solid by a series of heat treatments. Polymerization agents and photo-irradiation are investigated for their effects on YAG particle size and luminescence. The use of photo-irradiation led to the formation of a pure YAG phase at relatively low temperatures. In addition, photo-irradiation and polymerization agents slightly reduced particle size. X-ray induced luminescence spectroscopy was applied to examine the luminescence efficiency of CeYAG nanocrystals, revealing a strong luminescence at 525nm.