773 research outputs found
Mark Stockman, the knight of plasmonics
No full textMark Stockman, one of the founding members and pioneers of plasmonics and nanophotonics, passed away at the age of 73 on 11 November 2020 in Atlanta, Georgia, USA. Always at the front row of the conference hall, nodding in agreement or shaking his head in disapproval, Mark will be remembered not only for his breakthrough studies, but also for his passion for science and the uncompromising standards in research that he applied to himself and others. At every conferencesession, the speakers would be nervously waiting, with the audience, for Mark’s insightful questions
Bianisotropic Effective Parameters of Optical Metamagnetics and Negative-Index Materials
Get PDFApproaches to the adequate homogenization of optical metamaterials are becoming more and more complex, primarily due to an increased understanding of the role of asymmetric electrical and magnetic responses, in addition to the nonlocal effects of the surrounding medium, even in the simplest case of plane-wave illumination. The current trend in developing such advanced homogenization descriptions often relies on utilizing bianisotropic models as a base on top of which novel optical characterization techniques can be built. In this paper, we first briefly review general principles for developing a bianisotropic homogenization approach. Second, we present several examples validating and illustrating our approach using single-period passive and active optical metamaterials. We also show that the substrate may have a significant effect on the bianisotropic characteristics of otherwise symmetric passive and active metamaterials
Nanophotonics & Metamaterials
No full textThis course, instructed by Vlad Shalaev of Purdue University, aims to "cover nanoscale processes and devices and their applications for manipulating light on the nanoscale." The topics covered in this course are: Photonic crystals, Photonic crystal fibers, Photonic nanocircuits, Metal optics, Manipulating light with plasmonic nanostructures, Plasmonic nano-sensors, Near-field optics, and Metamaterials and negative refractive index and super-resolution. Here, visitors will find the course outline and syllabus, recommended readings, homework assignments, and weekly lecture notes. There is also a link to two online textbooks. This resource has plenty of assignment ideas and lecture materials to draw on for any educator's own nanotechnology classroom
Fabrication and realistic modeling of three-dimensional metal-dielectric composites
Get PDFHistorically, the methods used to describe the electromagnetic response of random, three-dimensional (3D), metal-dielectric composites (MDCs) have been limited to approximations such as effective-medium theories that employ easily-obtained, macroscopic parameters. Full-wave numerical simulations such as finite-difference time domain (FDTD) calculations are difficult for random MDCs due to the fact that the nanoscale geometry of a random composite is generally difficult to ascertain after fabrication. We have developed a fabrication method for creating semicontinuous metal films with arbitrary thicknesses and a modeling technique for such films using realistic geometries. We extended our two-dimensional simulation method to obtain realistic geometries of 3D MDC samples, and we obtained the detailed near-and far-field electromagnetic responses of such composites using FDTD calculations. Our simulation results agree quantitatively well with the experimentally measured far-field spectra of the real samples. (C) 2011 Society of Photo-Optical Instrumentation Engineers (SPIE). [DOI: 10.1117/1.3590208
Optical metamaterials: Basic structures and potential applications
No full textOptical metamaterials—artificially structured materials with engineered electromagnetic responses at optical frequencies—have exhibited optical properties not observed in their constituent materials and not found in nature. They extend the electromagnetic properties of usual optical media and allow unconventional material properties such as a negative magnetic permeability and a negative index of refraction. Optical metamaterials have enabled unprecedented flexibility in manipulating light waves and producing new functionalities. Among the many proposed metamaterial applications, two of the most prominent include the superlens that allows subwavelength resolution beyond the diffraction limit and the electromagnetic cloak, which promises the ultimate optical illusion—invisibility. We have studied various topics in this field, from basic structures to potential applications. Specifically, we experimentally demonstrated the first optical magnetic metamaterial across the whole visible spectrum, and we also demonstrated the first optical negative-index material exhibiting a negative refractive index of –0.3 at the telecommunication wavelength of ∼ 1.5 μm. As for the potential applications with optical metamaterials, we proposed and analyzed a near-field superlens based on a composite metal-dielectric film, which can operate at practically any desired wavelength in the visible and near-infrared ranges. We also investigated the possibility of constructing an optical cloak of invisibility and presented the first practical design of such a device. Further studies on the topic include improved cloaking performance using high-order transformations and conceptual designs for high-order optical cloaking devices
Quantum size and nonlinear effects in metal nanostructures and bio-applications with SERS
No full textWith the help of advances in nanotechnology, metal nanostructures have attracted much interest in various areas. Surface Enhanced Raman Spectroscopy is gaining high interest with new fabrication techniques and may find potential applications in biology and medicine. A possibility of SERS to see the difference between proteins with small structural changes, such as difference between human insulin (Humulin) and its artificial substitute Humalog or phosphorylation detection of 13-mer peptides, is demonstrated using semicontinuous silver film as an active substrate. A good quality spectrum could be obtained for as low as 25 amol of proteins, which makes it more suitable for applications in biology. The detection limit can be further improved by using a mixture of protein and polymer. The high sensitivity is mostly due to the high local fields, which are created in the gaps between particles. An investigation of nonlinear optical properties of colloids of silver nanoparticles using self-rotation of ellipse, Optical Kerr Effect (OKE), and Inverse Faraday Effect (IFE) also suggests that the biggest contribution to the enhancement of local field is coming from small clusters of particles, which are brought close to each other rather then big aggregates (100–1000 particles). A model of a Spherical Quantum Well have been implemented for describing two-photon excited luminescence from metal nanoparticles and shows a good agreement in experiment with colloid of silver nanoparticles. The results suggest that SERS is a powerful tool for numerous biological applications such as protein secondary structure and phosphorylation detection
Plasmonic Metasurfaces Utilizing Emerging Material Platforms
No full textMetasurfaces are broadly defined as artificially engineered material interfaces that have the ability to determinately control the amplitude and phase signatures of an incident electromagnetic wave. Subwavelength sized optical scatterers employed at the planar interface of two media, introduce abrupt modifications to impinged light characteristics. Arbitrary engineering of the optical interactions and the arrangement of the scatterers on plane, enable ultra-compact, miniaturized optical systems with a wide array of applications (e.g. nanoscale and nonlinear optics, sensing, detection, energy harvesting, information processing and so on) realizable by the metasurfaces. However, maturation from the laboratory to industry scale realistic systems remain largely elusive despite the expanding reach and vast domains of functionalities demonstrated by researchers. A large part of this multi-faceted problem stems from the practical constraints posed by the commonly used plasmonic materials that limit their applicability in devices requiring high temperature stability, robustness in varying ambient, mechanical durability, stable growth into nanoscale films, CMOS process compatibility, stable bio-compatibility, and so on.Aiming to create a whole-some solution, my research has focused on developing novel, high-performance, functional plasmonic metasurface devices that utilize the inherent benefits of various emerging and alternative material platforms. Among these, the two-dimensional MXenes and the refractory transition metal nitrides are of particular importance. By exploiting the plasmonic response of thin films of the titanium carbide MXene (Ti3C2Tx) in the near infrared spectral window, a highly broadband metamaterial absorber has been designed, fabricated and experimentally demonstrated. In another work, high efficiency photonic spin Hall Effect has been experimentally realized in robust phase gradient metasurface devices based on two different refractory transition metal nitrides –titanium nitride (TiN) and zirconium nitride (ZrN). Further, taking advantage of the refractory nature of these plasmonic nitrides, a metasurface based temperature sensor has been developed that is capable of remote, optical sensing of very high temperatures ranging up to 1200oC
Improving plasmonic nanoantennas for optical limiting
No full textIn this dissertation, the nanoantenna is used for the application of optical limiting. The strong local electromagnetic field enhancement in the small gap of the dipole nanoantenna gives it the ability to enhance nonlinear absorption. The first part of this dissertation will emphasize improving plasmonic nanoantennas. An annealing method, which can reduce the loss of gold nanoantennas and improve the plasmonic resonance, is described. By annealing the nanoantenna for two minutes at 400 degree Celsius, the Drude electron relaxation rate due to the grain boundaries is decreased by the factor of 3.2. In the second part of the dissertation, the laser damage threshold of the interaction between a short pulse laser and the nanoantenna is discussed. Thermal expansion occurs when the nanoantenna absorbs the laser energy at the resonance wavelength. To help avoid this damage, a dielectric film covering on the top of nanoantennas can be applied to increase the nanoantenna damage threshold by six times. This dissertation concludes with a discussion of the organic film (4, 4\u27-bis(diphenylamino)stilbene, BDPAS) deposition experiment and the z-scan measurement re of BDPAS thin film with nanoantennas. The z-scan result describes the 40 times enhancement of two photon absorption from the BDPAS thin film with nanoantennas
Transdimensional Plasmonic Titanium Nitride for Tailorable Nanophotonics
No full textIn the realm of tunable optical devices, 3D nanostructures with metals and dielectrics have been utilized in a wide variety of practical applications ranging from optical switching to beam-steering devices. 2D materials, on the other hand, have enabled the exploration of truly new physics unattainable with 3D systems due to quantum confinement leading to unique optical properties and enhanced light-matter interactions. Transdimensional materials (TDMs) – atomically thin films of metals – can couple the robustness of 3D nanostructures with the new physics enabled by 2D features. However, the evolution of the optical properties in the transdimensional regime between 3D and 2D is still underexplored. The optical properties of metallic TDMs are expected to show unprecedented tailorability, including strong dependences on the film thickness, composition, strain, and surface termination. They also have an increased sensitivity to external optical and electrical perturbations, owing to their extraordinary light-confinement. Additionally, the small atomic thicknesses may lead to strongly confined surface plasmons and quantum and nonlocal phenomena. The strong tunability and light-confinement offered by TDMs have resulted in a search for atomically thin plasmonic material platforms that facilitate active metasurfaces with novel functionalities in the visible and near infrared (NIR) range. In this research, we explore the plasmonic properties and tailorability of atomically thin titanium nitride (TiN). We experimentally and theoretically study the thickness-dependent optical properties of epitaxial TiN films with thicknesses down to 1 nm to demonstrate confinement induced optical properties. Overall, this research demonstrates the potential of TDMs for unlocking novel optical phenomena at visible and NIR wavelengths and realizing a new generation of atomically thin tunable nanophotonic devices
Novel Plasmonic Materials and Nanodevices for Integrated Quantum Photonics
No full textLight-matter interaction is the foundation for numerous important quantum optical phenomena, which may be harnessed to build practical devices with higher efficiency and unprecedented functionality. Nanoscale engineering is seen as a fruitful avenue to significantly strengthen light-matter interaction and also make quantum optical systems ultra-compact, scalable, and energy efficient. This research focuses on color centers in diamond that share quantum properties with single atoms. These systems promise a path for the realization of practical quantum devices such as nanoscale sensors, single-photon sources, and quantum memories. In particular, we explored an intriguing methodology of utilizing nanophotonic structures, such as hyperbolic metamaterials, nanoantennae, and plasmonic waveguides, to improve the color centers performance. We observed enhancement in the color center’s spontaneous emission rate, emission directionality, and cooperativity over a broad optical frequency range. Additionally, we studied the effect of plasmonic environments on the spin-readout sensitivity of color centers. The use of CMOS-compatible epitaxially grown plasmonic materials in the design of these nanophotonic structures promises a new level of performance for a variety of integrated room-temperature quantum devices based on diamond color centers
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