Bringing circuit functionalities into the optical domain requires the introduction of new conceptual paradigms and experimental methods, and would represent an important advance in nanoelectronics technology. In this seminar, I will introduce the lumped circuit elements in the near infrared regime by making use of plasmonic materials and simple geometries with subwavelength cross-sectional dimensions. The control of the functionality of these optical nanocircuits, completely consistent and analogous with the notion of radio-frequency circuits, and can be done by changing the impedances of the circuit elements. Such nanocircuits' elements function as building blocks for future plasmonic devices.

I will also present a novel structure that effectively behaves as an n=0 metastructure in the visible and near-infrared spectral range. This metal/dielectric optical waveguide structure operating at the cutoff of its TE mode behaving effectively as an Epsilon-Near-Zero (ENZ) metamaterial, exhibiting uniform phase distribution and essentially uniform amplitude, which enables opportunities for better control and enhancement of light propagation in waveguides, as well as development of nano-photonic devices. Finally, I will discuss the effect of the ENZ medium on the control of degree of coherence by comparing the field radiated by sources with varying degrees of randomness in a conventional medium to that in an ENZ medium.

Metamaterials, the artificial electromagnetic media with properties beyond those found in natural materials, have been a subject of intensive studies for over a decade and as the field evolves, new avenues for their applications are emerging. In this talk, I will focus on the possible applications of Fano resonant metamaterials stemming from their ability of enhancing light-matter interaction due to strong confinement of electromagnetic field by subradiant modes. I will show how metamaterials can be endowed with new unique functionalities by combining them with other complex media, such as magnetic materials, biomolecules, and graphene. In particular, the nonreciprocity can be engineered and ultra-thin optical diodes can be created by combining metamaterials with magneto-optical materials. It will also be shown how the interaction of high-quality mid-IR modes of Fano-resonant metamaterials with the vibrational modes of biomolecules facilitates the detection of protein monolayers and their characterization to an unprecedented degree. Finally, I will present our recent theoretical and experimental results on light scattering in metamaterial/graphene heterostructures and propose how such hybrid photonic-electronic systems can be used to build tunable photonic devices.

Plasmonics has opened the possibility to strongly enhance light-matter interaction at the nanoscale, opening new opportunities to manipulate and confine light at dimensions unthinkable only a few years ago. Plasmonic nanostructures can enhance weak optical responses and nonlinear optical effects, and can serve as information carriers for the next-generation of heavily integrated nanophotonic systems. Optical metamaterials formed by large arrays of subwavelength plasmonic nanostructures can open even more exciting scenarios, by exploiting the collective coupling interaction among many nanoinclusions to realize bulk optical properties that cannot be found in nature, such as a negative optical index of refraction. In my talk,I will describe our recent research efforts on optical nanoantenna arrays and optical metamaterials, studying their exciting physics and their practical use and application in highly-efficient thermoelectric and thermophotovoltaic solar cells, photothermal therapy and nanoscale nonlinear optical processes, including wave mixing, harmonic generation, phase conjugation and optical bistable effects. In addition, I will discuss how the extreme local field enhancement around nanoantennas can benefit ultrafast photon-assisted field emission processes, optical heterodyne terahertz (THz) generation and multiple-photon photoemission from nano-emitters, enabling compact, low-cost, low-power THz generation, free-electron lasers and X-ray sources. I will also discuss how the anti-phase polarization of a plasmonic coating may be used to realize invisibility and transparency effects. As an extreme case of light manipulation at the "atomic" scale, I will discuss the collective oscillation of massless Dirac fermions inside grapheme monolayers, in which surface plasmon polaritons may be controlled by the graphene's tunable surface conductivity using electrostatic gating. I will conclude my talk discussing active and tunable THz nanodevices and nanocircuits, and graphene-based THz metamaterials.

A hot body radiates an electromagnetic flux according to Kirchhoff's law. However, close to the body surface there are strong fluctuating fields which do not contribute to the electromagnetic flux. These fields are evanescent and decay exponentially away from the surface. Some phenomena, related to those fields, will be discussed and the effect of stationary currents on the electromagnetic field fluctuations will be pointed out.

Surface plasmons have been investigated intensively because of their unique properties for optical confinement and light manipulation on subwavelength scales. Research on both fundamentals and applications of surface plasmons are advanced by rapid development of nanoscale synthesis and fabrication techniques. By defining nanostructures in metals, these traditional electrical conductors are functionalized with plasmonic properties, which have led to exotic phenomena such as negative light refraction, surface enhanced Raman scattering, and subwavelength focusing. In this talk, I will discuss how surface plasmons in periodically patterned metals can be identified, characterized, and tuned using near-field and far-field optical methods. These periodic nanostructures, also known as plasmonic crystals, provide versatile platforms for discovering and screening new plasmonic materials. Rationally designed plasmonic crystals have also shown promises for applications from biochemical sensing to solar energy harvesting.

Diffraction effects are ubiquitous in all phenomena involving the propagation of waves. As an example, in optics and photonics the so-called "diffraction limit" imposes a fundamental limit on the resolution that an optical instrument can achieve, or on the confinement that a beam can maintain during propagation. In this talk I will present novel strategies to manage or to completely counteract the effects of diffraction. The far reaching consequences of the proposed schemes include the possibility of achieving far-field sub-diffraction imaging, evanescent wave recovery and diffraction-free, self-healing plasmonic propagation.

The concept of multi-dimensional Fourier transform spectroscopy originated in nuclear magnetic resonance (NMR) where it revolutionized NMR studies of molecular structure and dynamics and led to the Nobel Prize in Chemistry in 1991. In the past decade, the same concept has been implemented in the optical region with femtosecond lasers. In the experiment, the nonlinear response of a sample to multiple laser pulses is measured as a function of time delays. A multi-dimensional spectrum is constructed by taking a multi-dimensional Fourier transform of the signal with respect to multiple time delays.
In this presentation, I will introduce optical multi-dimensional Fourier transform spectroscopy and its applications to study a potassium (K) vapor and semiconductor nanostructures. The K vapor provides a simple test model to validate the method, while the obtained 2D spectra reveal the surprising collective resonance due to the dipole-dipole interaction in a dilute gas. By extending the technique into a third dimension, 3D spectra can unravel different pathways in a quantum process and provide complete and unambiguous information to construct the full Hamiltonian of the system. Besides atomic/molecular systems, optical multi-dimensional Fourier-transform spectroscopy is also a powerful tool for studying many-body dynamics and coupling in solid-state systems such as semiconductor nanostructures. I will present several applications in semiconductor quantum wells and self-assembled quantum dots, where unique information about the systems can be obtained from 2D spectra.

Quantum states of light have been shown to provide improvements in a variety of systems, resulting in provably secure communication, sub-shot noise interferometry, and computation schemes that scale better with resources than when using classical means. A key aspect of these entangled and squeezed states of light is that they exhibit correlations that are stronger than allowed classically. Due to the important role entanglement plays in the field of quantum optics, numerous investigations into its fundamental behavior have taken place. For example, how entanglement evolves when propagating through a slow light medium, in which the group velocity of light is less than the speed of light in vacuum, c, have been conducted in the past. We seek to investigate how quantum correlations and entanglement behave when propagating through a medium exhibiting anomalous dispersion. In such a medium, optical pulses may propagate with group velocities that are larger than c, or even negative. In this talk I will show that by using a nondegenerate four-wave mixing (4WM) process in warm rubidium vapor, which may be used to generate squeezed and entangled states of light, it is possible to generate pulses with record negative group velocities. Additionally, I will discuss recent results involving the combination of fast light and quantum entanglement. Finally, I will present ongoing research involving secure quantum key distribution and phase-sensitive image amplification, and conclude with a discussion of future research directions involving the versatile 4WM system.

This talk focuses on the statistical mechanics of micrometer colloidal particles moving through landscapes of force and torque that are created with computer-generated holograms. These optical force fields can take the form of discrete optical tweezers that can trap and hold microscopic objects in three dimensions. They also can be far more exotic, and include the first experimental implementation of a knotted force field, and the first successful demonstration of a true tractor beam. In addition to the conservative forces that create traps, holographically structured light fields also exert non-conservative forces whose intriguing ramifications we observe with holographic video microscopy. These observations reveal a previously unrecognized category of stochastic heat engines.