Alexey V. Krasavin

Passive photonic elements based on dielectric-loaded surface plasmon polariton waveguides

The authors present full three-dimensional numerical modeling of passive photonic elements based on dielectric-loaded surface plasmon polariton waveguides (DLSPPWs). They demonstrate that at telecom wavelengths a highly confined SPP mode can be guided in a single mode DLSPPW of subwavelength cross section and estimate the achievable density of photonic integration. The size of bending and splitting photonic elements based on DLSPPW can be as small as a few micrometers with pure bend loss less than 10% (0.4dB) and the transmission efficiency exceeding 70% (total loss of about 1.3dB). Such DLSPPW elements are important for implementation of photonic integrated circuits, guiding optical and electric signals in the same circuitry, and lab-on-a-chip applications.

Silicon-based plasmonic waveguides.

We propose and comprehensively investigate Si-based plasmonic waveguides as a means to confine and manipulate photonic signals. The high refractive index of Si assures strong confinement and a very high level of photonic integration with achievable waveguide separations of the order of 10 nm and waveguide bends with 500 nm radius at telecommunication wavelengths, while using Al and Cu plasmonic material platforms, makes such waveguides fully compatible with existing CMOS fabrication processes. Their potential future in hybrid electronic/photonic chips is further reinforced as various configurations have been shown to compensate SPP propagation loss. The group velocity dispersion of such waveguides allows over 10 Tb/s signal transfer rates. The figures of merit allowing comparison of passive and active functionalities achievable with various waveguides have also been introduced.

Bend- and splitting loss of dielectric-loaded surface plasmon-polariton waveguides

The design, fabrication, characterization, and modeling of basic building blocks of plasmonic circuitry based on dielectric-loaded surface polariton waveguides, such as bends, splitters, and Mach-Zehnder interferometers are presented. The plasmonic components are realized by depositing subwavelength dielectric ridges on a smooth gold film using mass-production-compatible UV-photolithography. The near-field characterization at telecommunication wavelengths shows the strong mode confinement and low radiation and bend losses. The performance of the devices is found in good agreement with results obtained by full vectorial three-dimensional finite element simulations.

Amplified spontaneous emission of surface plasmon polaritons and limitations on the increase of their propagation length

Amplified spontaneous emission of surface plasmon polaritons (SPPs) at the interface of a resonant gain medium has been observed. The amplification is accompanied by significant spectral narrowing and limits the gain available for compensation of SPP propagation losses. The effect is similar to the deteriorating influence of amplified spontaneous emission in laser resonators.

Wavelength selection by dielectric-loaded plasmonic components

Fabrication, characterization, and modeling of waveguide-ring resonators and in-line Bragg gratings for wavelength selection in the telecommunication range are reported utilizing dielectric-loaded surface plasmon-polariton waveguides. The devices were fabricated by depositing subwavelength-sized polymer ridges on a smooth gold film using industrially compatible large-scale UV photolithography. We demonstrate efficient and compact wavelength-selective filters, including waveguide-ring resonators with an insertion loss of ∼2u2002dB and a footprint of only 150u2002μm2 featuring narrow bandwidth (∼20u2002nm) and high contrast (∼13u2002dB) features in the transmission spectrum. The performance of the components is found in good agreement with the results obtained by full vectorial three-dimensional finite element simulations.

Wavelength-selective directional coupling with dielectric-loaded plasmonic waveguides

We consider wavelength-selective splitting of radiation using directional couplers (DCs) formed by dielectric-loaded surface-plasmon-polariton waveguides (DLSPPWs). The DCs were fabricated by depositing sub-wavelength-sized polymer ridges on a gold film using large-scale UV photolithography and characterized at telecommunications wavelengths with near-field microscopy. We demonstrate a DLSPPW-based 45-microm-long DC comprising 3 microm offset S bends and 25-microm-long parallel waveguides that changes from the through state at 1500 nm to 3 dB splitting at 1600 nm, and show that a 50.5-microm-long DC should enable complete separation of the radiation channels at 1400 and 1620 nm. The DC performance is found to be in good agreement with full vectorial three-dimensional finite-element simulations.

Electro-optic switching element for dielectric-loaded surface plasmon polariton waveguides

We present three-dimensional numerical modeling of an active electronically controlled switching element for fully-functional plasmonic circuits based on dielectric-loaded surface plasmon polariton waveguides. It has been demonstrated that the transmission of the guided mode through a highly wavelength-selective waveguide ring resonator (WRR) can be efficiently controlled with very small refractive index changes of the order of 10−3, achievable through the electro-optic effect in nonlinear materials. Furthermore, we have introduced a figure of merit for such active plasmonic elements and optimized the active WRR performance in terms of its sensitivity and size. These results shows the potential to create high performance 600 nm radius plasmonic WRR switches.

Numerical analysis of long-range surface plasmon polariton modes in nanoscale plasmonic waveguides

Guiding properties of nanoscale metallic wire waveguides embedded in a semiconductor are discussed. By performing eigenmode numerical simulations of the waveguide and continually varying the geometrical cross-section parameters, we have obtained comprehensive mode characteristics, such as the effective refractive index, effective mode area, and propagation length, that provide full guided mode description. This allows us to gain insight into possible waveguide applications using the figures of merit. Amplification and polarization manipulation of a plasmonic signal in such a waveguide have also been considered.

Active components for integrated plasmonic circuits

We present a comprehensive study of highly efficient and compact passive and active components for integrated plasmonic circuit based on dielectric-loaded surface plasmon polariton waveguides.

Electrically-driven metamaterials (Conference Presentation)

Electric excitation of plasmonic guided modes in integrated circuits is important for the development of compact optical signal processing components as well integrated bio- and chemical sensing applications. Surface plasmons in purely metallic nanostructures are typically excited by external illumination or high-energy (keV) electron beams. Low-energy inelastic electron tunnelling is an alternative way to excite surface plasmons in ambient environment with the advantages of high compactness and background free operation, and has been widely investigated using metal-insulator-metal structures and in scanning tunnelling microscopy. Recently, it has been demonstrated that optical antennas or molecules can be used to strongly enhance the electron-photon conversion efficiency and/or control the related light emission on chip scale, opening up opportunities for the practical application of tunnelling-electron-driven plasmonic devices and components. At the same time, the tunnelling behavior is extremely sensitive to the immediate property change of a medium placed in the tunnel path, which holds great opportunities for the development of tunnelling-based devices for the dynamical control of plasmons or the detections of environmental changes with high sensitivity. Here we will discuss hot-electron excitation in electrically-driven plasmonic nanorod metamaterials and their applications for light emission and gas sensing, including hydrogen and oxygen gases. Electrically-driven plasmonic nanorod metamaterials comprise a fertile platform merging photonics, electronics and chemistry, opening up opportunities for developing electron tunnelling-based nanoscale devices for light generation and modulators and chemical sensing.