Novel approaches to control the propagation of electromagnetic waves : metamaterials and photonic crystals

Cataloged from PDF version of article.Applications in areas such as photonics, antennas, imaging and optics require the control of propagation of electromagnetic waves and the control of emission of electromagnetic radiation. Achievements in three key research fields may provide the answer to these problems. These emerging research fields are metamaterials, photonic crystals and surface plasmons. This thesis will be about our work on metamaterials and photonic crystals. Metamaterials are a new class of artificial structures whose electromagnetic response can be described by effective permeability and permittivity functions that may attain negative values. I will present our results on the properties of a metamaterial structure that we proposed recently, the labyrinth structure. I will demonstrate that the labyrinth structure can be used to design a medium that exhibits negative permeability values within a certain frequency range. Moreover, I will explore the possibility of negative refraction and sub-wavelength focusing of electromagnetic waves by two and threedimensional labyrinth structure based left-handed mediums. Novel applications such as metamaterial based compact size antennas, ultra-small high-Q cavities will be also discussed. Another type of artificial electromagnetic structures are the photonic crystals. Photonic crystals can be described by a periodic modulation of the permittivity and/or the permeability of a medium. I will discuss two phenomena arising from the dispersion properties of photonic crystals and their possible applications. One of these phenomena is the existence of surfacebound electromagnetic modes and the other is the negative refraction effect. I will further show that the surface-bound modes can be used for applications such as beaming of electromagnetic waves and enhancement of transmission through sub-wavelength apertures. In addition, I will demonstrate that the negative refraction effect can be utilized to focus electromagnetic waves emitted from a finite size source.Bulu, İrfanPh.D

Radiation properties of sources inside photonic crystals

Cataloged from PDF version of article.The control of spontaneous emission is an important problem both in basic and applied physics. Two main problems arise in the control of emission: enhancement or suppression and angular confinement of radiation. In this work we studied the properties of emission of radiation from a localized microwave source embedded inside a photonic crystal. We showed that by using a photonic crystal it is possible to enhance the emitted power. We achieved up to 22 times enhancement of power at the band edge of the photonic crystal. We also studied the properties of emission of radiation from a source embedded inside a single defect structure and embedded inside a coupled defect structure. Enhanced emission for single defect and coupled defect structures was also observed. Moreover, angular distribution of power from a localized microwave source embedded inside a photonic crystal was studied. Angular confinement was achieved near the band edge of the photonic crystal. Half power beam widths as small as 6 degrees were obtained. This is the smallest half power beam width in the literature obtained by using photonic crystals. We also investigated frequency and size dependence of the angular distribution. We observed that the angular confinement strongly depends on frequency and on the size of the photonic crystal. In fact, we showed that angular confinement could be obtained just at the band edge frequency. In conclusion, our work showed that the problem of controlling the spontaneous emission could be solved at once by using photonic crystals.Bulu, İrfanM.S

Broadband Waveguide QED System on a Chip

We demonstrate that a slot waveguide provides a broadband loss-free platform suitable for applications in quantum optics. We find that strong coupling between light quanta and a single quantum emitter placed in the waveguide slot can be achieved with efficiency higher than 96% and Purcell factor (spontaneous emission factor) larger than 200. The proposed system is a promising platform for quantum information processing and can be used to realize an efficient single photon source and optically addressable photon register.Engineering and Applied Science

Single Color Centers Implanted in Diamond Nanostructures

The development of materials processing techniques for optical diamond nanostructures containing a single color center is an important problem in quantum science and technology. In this work, we present the combination of ion implantation and top-down diamond nanofabrication in two scenarios: diamond nanopillars and diamond nanowires. The first device consists of a 'shallow' implant (~20nm) to generate Nitrogen-vacancy (NV) color centers near the top surface of the diamond crystal. Individual NV centers are then isolated mechanically by dry etching a regular array of nanopillars in the diamond surface. Photon anti-bunching measurements indicate that a high yield (>10%) of the devices contain a single NV center. The second device demonstrates 'deep' (~1\mu m) implantation of individual NV centers into pre-fabricated diamond nanowire. The high single photon flux of the nanowire geometry, combined with the low background fluorescence of the ultrapure diamond, allows us to sustain strong photon anti-bunching even at high pump powers.Comment: 20 pages, 7 figure

Plasmonic resonators for enhanced diamond NV- center single photon sources

We propose a novel source of non-classical light consisting of plasmonic aperture with single-crystal diamond containing a single Nitrogen-Vacancy (NV) color center. Theoretical calculations of optimal structures show that these devices can simultaneously enhance optical pumping by a factor of 7, spontaneous emission rates by Fp ~ 50 (Purcell factor), and offer collection efficiencies up to 40%. These excitation and collection enhancements occur over a broad range of wavelengths (~30nm), and are independently tunable with device geometry, across the excitation (~530nm) and emission (~600-800nm) spectrum of the NV center. Implementing this system with top-down techniques in bulk diamond crystals will provide a scalable architecture for a myriad of diamond NV center applications.Comment: 9 pages, 7 figure

Optomechanical and photothermal interactions in suspended photonic crystal membranes

We present here an optomechanical system fabricated with novel stress management techniques that allow us to suspend an ultrathin defect-free silicon photonic-crystal membrane above a Silicon-on-Insulator (SOI) substrate with a gap that is tunable to below 200 nm. Our devices are able to generate strong attractive and repulsive optical forces over a large surface area with simple in- and out- coupling and feature the strongest repulsive optomechanical coupling in any geometry to date (g[subscript OM]/2π ≈ −65 GHz/nm). The interplay between the optomechanical and photo-thermal-mechanical dynamics is explored, and the latter is used to achieve cooling and amplification of the mechanical mode, demonstrating that our platform is well-suited for potential applications in low-power mass, force, and refractive-index sensing as well as optomechanical accelerometry.United States. Defense Advanced Research Projects Agency. (Contract N66001-09-1-2070-DOD)National Science Foundation (U.S.) (CAREER Grant

Single-Color Centers Implanted in Diamond Nanostructures

The development of material-processing techniques that can be used to generate optical diamond nanostructures containing a single-color center is an important problem in quantum science and technology. In this work, we present the combination of ion implantation and top-down diamond nanofabrication in two scenarios: diamond nanopillars and diamond nanowires. The first device consists of a 'shallow' implant (similar to 20 nm) to generate nitrogen-vacancy (NV) color centers near the top surface of the diamond crystal prior to device fabrication. Individual NV centers are then mechanically isolated by etching a regular array of nanopillars in the diamond surface. Photon anti-bunching measurements indicate that a high yield (> 10%) of the devices contain a single NV center. The second device demonstrates 'deep' (similar to $1 \mu m$) implantation of individual NV centers into diamond nanowires as a post-processing step. The high single-photon flux of the nanowire geometry, combined with the low background fluorescence of the ultrapure diamond, allowed us to observe sustained photon anti-bunching even at high pump powers.Engineering and Applied SciencesPhysic

A study of thermally-induced optical bistability and the role of surface treatments in Si-based mid-infrared photonic crystal cavities

We report the observation of optical bistability in Si-based photonic crystal cavities operating around 4.5 \mum. Time domain measurements indicate that the source of this optical bistability is thermal, with a time constant on the order of 5 \mus. Quality (Q) factor improvement is shown by the use of surface treatments (wet processes and annealing), resulting in an increase of Q-factor from 11,500 to 29,300 at 4.48 \mum. After annealing in a N2 environment, optical bistability is no longer seen in our cavities