Ilya A. Rodionov

Plasmonic nanolaser for intracavity spectroscopy and sensorics

We demonstrate intracavity plasmonic laser spectroscopy using a plasmonic laser created from a periodically-perforated silver film with a liquid gain medium. An active zone of the laser is formed by a highly elongated spot of pumping. This results in an 80x decrease in the threshold pumping level; in a significantly more efficient diffusive mixing of dye molecules, which substantially suppresses the effect of their bleaching; and in the ability to reduce the volume of the gain medium to as little as 400 nL. We use this design for a stable plasmonic laser in multiple measurements and demonstrate that it is highly effective as a spaser spectroscopy sensor for intracavity detection of an absorptive dye at 70 ppb. This work provides an opportunity to develop applications of intracavity plasmonic laser spectroscopy in biological label detection and other fields.

Ultrabright Room-Temperature Sub-Nanosecond Emission from Single Nitrogen-Vacancy Centers Coupled to Nanopatch Antennas

Solid-state quantum emitters are in high demand for emerging technologies such as advanced sensing and quantum information processing. Generally, these emitters are not sufficiently bright for practical applications, and a promising solution consists in coupling them to plasmonic nanostructures. Plasmonic nanostructures support broadband modes, making it possible to speed up the fluorescence emission in room-temperature emitters by several orders of magnitude. However, one has not yet achieved such a fluorescence lifetime shortening without a substantial loss in emission efficiency, largely because of strong absorption in metals and emitter bleaching. Here, we demonstrate ultrabright single-photon emission from photostable nitrogen-vacancy (NV) centers in nanodiamonds coupled to plasmonic nanocavities made of low-loss single-crystalline silver. We observe a 70-fold difference between the average fluorescence lifetimes and a 90-fold increase in the average detected saturated intensity. The nanocavity-coupled NVs produce up to 35 million photon counts per second, several times more than the previously reported rates from room-temperature quantum emitters.

Light localization and SERS in tip-shaped silicon metasurface

Optical properties of two dimensional periodic system of the silicon micro-cones are investigated. The metasurface, composed of the silicon tips, shows enhancement of the local optical field. Finite element computer simulations as well as real experiment reveal anomalous optical response of the dielectric metasurface due to excitation of the dielectric resonances. Various electromagnetic resonances are considered in the dielectric cone. The metal-dielectric resonances, which are excited between metal nanoparticles and dielectric cones, are also considered. The resonance local electric field can be much larger than the field in the usual surface plasmon resonances. To investigate local electric field the signal molecules are deposited on the metal nanoparticles. We demonstrate enhancement of the electromagnetic field and Raman signal from the complex of DTNB acid molecules and gold nanoparticles, which are distributed over the metasurface. The metasurfaces composed from the dielectric resonators can have quasi-continuous spectrum and serve as an efficient SERS substrates.

Mass production compatible fabrication techniques of single-crystalline silver metamaterials and plasmonics devices

During last 20 years, great results in metamaterials and plasmonic nanostructures fabrication were obtained. However, large ohmic losses in metals and mass production compatibility still represent the most serious challenge that obstruct progress in the fields of metamaterials and plasmonics. Many recent research are primarily focused on developing low-loss alternative materials, such as nitrides, II–VI semiconductor oxides, high-doped semiconductors, or two-dimensional materials. In this work, we demonstrate that our perfectly fabricated silver films can be an effective low-loss material system, as theoretically well-known. We present a fabrication technology of plasmonic and metamaterial nanodevices on transparent (quartz, mica) and non-transparent (silicon) substrates by means of e-beam lithography and ICP dry etch instead of a commonly-used focused ion beam (FIB) technology. We eliminate negative influence of litho-etch steps on silver films quality and fabricate square millimeter area devices with different topologies and perfect sub-100 nm dimensions reproducibility. Our silver non-damage fabrication scheme is tested on trial manufacture of spasers, plasmonic sensors and waveguides, metasurfaces, etc. These results can be used as a flexible device manufacture platform for a broad range of practical applications in optoelectronics, communications, photovoltaics and biotechnology.

Colloidal suspensions in external rotating electric field: experimental studies and prospective applications in physics, material science, and biomedicine

Colloidal suspensions and tunable self-assembly of colloidal particles attract a great interest in recent years. In this paper, we propose a new setup and technology for studies of self-assembly of colloidal particles, interection of which between themselves is tuned by external rotating electric fields. We reveal wide prospectives of electric field employment for tunable self-assembly, from suspensions of inorganic particles to ensembles of biological cells. These results make enable particle-resolved studies of various collective phenomena and fundamental processes in many-particle systems in equilibrium state and far from it, while the dynamics can be resolved at the level of individual particles using video microscopy. For the first time, we demonstrate that, apart from ability to prepare photonic crystalline films of inorganic silica particles, the tunable self-assembly provides a novel technological way for manipulation with ensembles of biological cells by control of interactions between them.

Toward a theoretically limited SPP propagation length above two hundred microns on an ultra-smooth silver surface [Invited]

We demonstrate the optical medium for surface plasmon-polariton wave (SPP) propagation with ultra low losses corresponding to the theoretically limited values. The unique element of the optical medium is an atomically-flat single-crystalline silver thin film that provides extremely low losses. The SPP excited on the surface of such thin films (λ = 780 nm) is characterized by a SPP propagation length equal to 200 µm, which is twice longer than previously reported experimental results and corresponds to theoretically limited values for silver films.

Highly directional plasmonic nanolaser based on high-performance noble metal film photonic crystal

A fundamental problem in the integration of photonic elements is the problem of the light localization and the creation of nanolocalized laser sources of radiation. A new approach in the miniaturization of lasers is the approach based on using plasmon fields instead of photon fields. Plasmons arise from the interaction of the oscillations of the electron density and the electromagnetic fields that excite them. Accordingly, the electromagnetic effects caused by these fields occur in the subwavelength region near the surfaces, namely, in the nanometer range. Therefore, the approach allows to overcome the diffraction limitation on the laser size. Plasmonic nanolaser is a nanoscale (at least in one dimension) quantum generator of nanolocalized coherent plasmon fields. The nanoscopic in all three dimensions plasmon nanolaser has a different name: SPASER (Surface Plasmon Amplification by Stimulated Emission of Radiation). It is based on patterned metal film. The precision of formed structures and the dielectric properties of the metal are critical factors in determining any plasmonic device performance. Surface and morphology inhomogeneities should be minimized to avoid SPP scattering during propagation and etching anisotropy. Moreover, the metal should have high conductivity and low optical absorption to enhance optical properties and reduce losses. Some researchers focused on developing new low-loss materials (nitrides, highly-doped semiconductors, semiconductors oxides, or two-dimensional materials), but silver and gold are the most commonly used materials in optics and plasmonics due the lowest optical losses in visible and near infrared wavelength range. Recently, we have presented plasmonic nanolaser built on ultra-smooth silver films. Nanoscale structure in metallic films are typically fabricated by a two-step process. Metals are first deposited using evaporation or sputtering on a substrate and then patterned with focused-ion-beam milling or e-beam lithography and dry etching. If the deposited films are polycrystalline, etch rates vary for different grain orientations and grain boundaries. Therefore, the patterned structures could differ from each other. One of the possible solutions is to deposit singlecrystalline metals, which will be etched more uniformly and lead to precise structures. Another approach deals with large grain (<300 nm) polycrystalline film preparation. The fabricated silver films showed ultra-low losses (40 cm−1). Built on it a plasmonic laser demonstrated the lasing at 628 nm with a linewidth of 1.7 nm and a directivity of 1.3.

Metal-dielectric resonances in tip silicon metasurface and SERS based nanosensors

Optical properties of two-dimensional periodic systems of the dielectric micro bars and micro cones are investigated. Computer simulations as well as real experiment reveal anomalous optical response of the dielectric metasurface due to excitation of the dielectric and metal-dielectric resonances, which are excited in-between metal nanoparticles and dielectric cones and bars. In the metal-dielectric resonance local electric field can be orders on magnitude larger than the field in the plasmon resonance only. To investigate local electric field the signal molecules were deposited on the metal nanoparticles. We demonstrate the enhancement of the electro- magnetic field by detecting the Raman signal from the of organic acid molecules deposited on the investigated metasurface.

Poly(p-xylylene) Silver Nanocomposites: Optical, Radiative, and Structural Properties

We perform a detailed investigation of coatings made of poly(p-xylylene) nanocomposites with embedded silver nanoparticles of sizes up to 12 nm and concentration up to 10.5 vol. %. We study their microstructure, mechanical, optical, and radiative characteristics. We reveal certain correlations between structural peculiarities and optical, as well as radiative properties. These correlations are due to fluctuations in distribution of nanoparticles in a polymer matrix and also due to the peculiarities of nanoparticles size distribution. We calculated optical dispersion coefficients for nanocomposites with different silver content. It was shown the refractive index ( n) and extinction coefficient (k) is strongly dependent on the silver content and change within the 1.4–2.4 for n and 0–0.6 for the k. It is argued that poly(p-xylylene)silver nanocomposites can be used to construct multilayer coatings with required optical constant and conformal to any complex morphology.