A.E. Nikolaenko

Graphene in a photonic metamaterial

We demonstrate a photonic metamaterial that shows extraordinary sensitivity to the presence of a single atomic layer of graphene on its surface. Metamaterials optical transmission increases multi-fold at the resonance frequency linked to the Fano-type plasmonic mode supported by the periodic metallic nanostructure. The experiments were performed with chemical vapor deposited (CVD) graphene covering a number of size-scaled metamaterial samples with plasmonic modes at different frequencies ranging from 167 to 187 Thz.

Carbon nanotubes in a photonic metamaterial

Hybridization of single-walled carbon nanotubes with plasmonic metamaterials leads to photonic media with an exceptionally strong ultrafast nonlinearity. This behavior is underpinned by strong coupling of the nanotube excitonic response to the weakly radiating Fano-type resonant plasmonic modes that can be tailored by metamaterial design.

Nanostructured Plasmonic Medium for Terahertz Bandwidth All-Optical Switching

Periodic nanostructuring can enhance the optical nonlinearity of plasmonic metals by several orders of magnitude. By patterning a gold film, the largest sub-100 femtosecond nonlinearity is achieved, which is suitable for terahertz rate all-optical data processing as well as ultrafast optical limiters and saturable absorbers.

Thermally Activated Delayed Fluorescence in Polymers: A New Route toward Highly Efficient Solution Processable OLEDs

Efficient intermonomer thermally activated delayed fluorescence is demonstrated for the first time, opening a new route to achieving high-efficiency solution processable polymer light-emitting device materials. External quantum efficiency (EQE) of up to 10% is achieved in a simple fully solution-processed device structure, and routes for further EQE improvement identified.

Nonlinear graphene metamaterial

We demonstrate that the broadband nonlinear optical response of graphene can be resonantly enhanced by more than an order of magnitude through hybridization with a plasmonic metamaterial, while retaining an ultrafast nonlinear response time of ~1 ps. Transmission modulation close to ~1% is seen at a pump fluence of ~30 µJ/cm2 at the wavelength of ~1:6 µm. This approach allows to engineer and enhance graphene’s nonlinearity within a broad wavelength range enabling applications in optical switching, mode-locking, and pulse shaping.

THz bandwidth optical switching with carbon nanotube metamaterial

We provide the first demonstration of exceptional light-with-light optical switching performance of a carbon nanotube metamaterial - a hybrid nanostructure of a plasmonic metamaterial with semiconducting single-walled carbon nanotubes. A modulation depth of 10% in the near-IR with sub-500 fs response time is achieved with a pump fluence of just 10 μJ/cm², which is an order of magnitude lower than in previously reported artificial nanostructures. The improved switching characteristics of the carbon nanotube metamaterial are defined by an excitonic nonlinearity of carbon nanotubes resonantly enhanced by a concentration of local fields in the metamaterial. Since the spectral position of the excitonic response and metamaterial plasmonic resonance can be adjusted by using carbon nanotubes of different diameter and scaling of the metamaterial design, the giant nonlinear response of the hybrid metamaterial - in principle - can be engineered to cover the entire second and third telecom windows, from O- to U-band.

Cathodo- and photoluminescence in Yb3+-Er3+ co-doped PbF2 nanoparticles

We have prepared and studied the PbF(2):(Yb(3+),Er(3+)) co-doped nanoparticles, with chemical formula (Yb-Er)(x)Pb(1-x)F(2+x), where x = 0.29, Yb(3+)/Er(3+) = 6, and estimated the energy efficiency for their cathodoluminescence, mostly of Yb(3+), and up-conversion photoluminescence of Er(3+) to reach more than 0.5% and 20%, respectively, which may be the highest to date for rare-earth doped nanoparticles. Electron beam induced temperature rise in the nanoparticles has been estimated by measuring the ratio of green emission bands of Er(3+). These high efficiencies are due to high doping level of nanoparticles and due to low phonon energy of the PbF(2) host.

A meta-diffraction-grating for visible light

We report an experimental realization of a visible range planar diffraction grating, formed by sub-wavelength elements, with periodically variable parameters. At normal incidence the grating exhibits asymmetric diffraction into the positive and negative first diffraction orders and operates at visible wavelengths with peak efficiency at 736 nm wavelength.

Analytical model for active metamaterials with quantum ingredients

We present an analytical model describing complex dynamics of a hybrid nonlinear system consisting of interacting carbon nanotubes (CNT) and a plasmonic metamaterial. Our model is based on the set of coupled equations, which incorporates well-established density matrix formalism appropriate for quantum systems (CNT are described as a two level system) and harmonic-oscillator approach ideal for modelling sub-wavelength plasmonic and optical resonators. We show that the saturation nonlinearity of CNT increases multifold in the resonantly enhanced near field of a metamaterial. In the framework of our model, we discuss the effect of inhomogeneity of the CNT layer (band gap value distribution) on the nonlinearity enhancement. It is shown, that the Purcell effect is indistinguishable from the field enhancement and is described by the same phenomenological constant.We present an analytical model for describing complex dynamics of a hybrid system consisting of interacting classical and quantum resonant structures. Classical structures in our model correspond to plasmonic nano-resonators of different geometries, as well as other types of nano- and micro-structures optical response of which can be described without invoking quantum-mechanical treatment. Quantum structures are represented by atoms or molecules, or their aggregates (for example, quantum dots and carbon nanotubes), which can be accurately modelled only with the use of quantum approach. Our model is based on the set of equations that combines well-established density matrix formalism appropriate for quantum systems, coupled with harmonic-oscillator equations ideal for modelling sub-wavelength plasmonic and optical resonators. This model can also be straightforwardly adopted for describing electromagnetic dynamics of various hybrid systems outside the photonics realm, such as Josephson-junction metamaterials, or SQUID elements coupled with an RF strip resonator.

Transformation optics with planar metamaterials: Diffraction grating and lens

We use the resonance properties of elemental building blocks of metamaterial array with spatially variable parameter to control the phase and intensity of light beam. Dispersive and focusing devices are reported for the first time.