Evgeniy Panchenko

Electron paramagnetic resonance microscopy using spins in diamond under ambient conditions

Magnetic resonance spectroscopy is one of the most important tools in chemical and bio-medical research. However, sensitivity limitations typically restrict imaging resolution to ~ 10 µm. Here we bring quantum control to the detection of chemical systems to demonstrate high-resolution electron spin imaging using the quantum properties of an array of nitrogen-vacancy centres in diamond. Our electron paramagnetic resonance microscope selectively images electronic spin species by precisely tuning a magnetic field to bring the quantum probes into resonance with the external target spins. This provides diffraction limited spatial resolution of the target spin species over a field of view of 50 × 50 µm2 with a spin sensitivity of 104 spins per voxel or ∼100 zmol. The ability to perform spectroscopy and dynamically monitor spin-dependent redox reactions at these scales enables the development of electron spin resonance and zepto-chemistry in the physical and life sciences.Electron paramagnetic resonance spectroscopy has important scientific and medical uses but improving the resolution of conventional methods requires cryogenic, vacuum environments. Simpson et al. show nitrogen vacancy centres can be used for sub-micronmetre imaging with improved sensitivity in ambient conditions.

Modified stripe waveguide design for plasmonic input port structures

Abstract. We present a modified asymmetric stripe plasmonic waveguide design for plasmonic integrated input port structures. Such a waveguide shape can significantly increase the surface plasmon polariton (SPP) propagation length. A computational investigation of the waveguide mode analysis, excitation, and guiding is presented as well as SPP propagation length improvement strategies. The proposed structure has the potential to be CMOS compatible and could be used in highly integrated optoelectric circuits.

Cathodoluminescence as a probe of the optical properties of resonant apertures in a metallic film

Here we present the results of an investigation of resonances of azimuthal trimer arrangements of rectangular slots in a gold film on a glass substrate using cathodoluminescence (CL) as a probe. The variation in the CL signal collected from specific locations on the sample as a function of wavelength and the spatial dependence of emission into different wavelength bands provides considerable insight into the resonant modes, particularly sub-radiant modes, of these apertures. By comparing our experimental results with electromagnetic simulations we are able to identify a Fabry–Pérot mode of these cavities as well as resonances associated with the excitation of surface plasmon polaritons on the air–gold boundary. We obtain evidence for the excitation of dark (also known as sub-radiant) modes of apertures and aperture ensembles.

Plasmonics-enabled metal-semiconductor-metal photodiodes for high-speed interconnects and polarization sensitive detectors

Metal-semiconductor-metal (MSM) photodiodes are commonly used in ultrafast photoelectronic devices. Recently it was shown that localized surface plasmons can sufficiently enhance photodetector capabilities at both infrared and visible wavelengths. Such structures are of great interest since they can be used for fast, broadband detection. By utilizing the properties of plasmonic structures it is possible to design photodetectors that are sensitive to the polarization state of the incident wave. The direct electrical readout of the polarization state of an incident optical beam has many important applications, especially in telecommunications, bio-imaging and photonic computing. Furthermore, the fact that surface plasmon polaritons can circumvent the diffraction limit, opens up significant opportunities to use them to guide signals between logic gates in modern integrated circuits where small dimensions are highly desirable. Here we demonstrate two MSM photodetectors integrated with aluminum nanoantennas capable of distinguishing orthogonal states of either linearly or circularly polarized light with no additional filters. The localized plasmon resonances of the antennas lead to selective screening of the underlying silicon from light with a particular polarization state. The non-null response of the devices to each of the basis states expands the potential utility of the photodetectors while improving precision. We also demonstrate a design of waveguide-coupled MSM photodetector suitable for planar detection of surface plasmons.

Nanometers to centimeters: novel optical nano-antennas, with an eye to scaled production

Optical nano-antennas have been the focus of intense research recently due to their ability to manipulate electromagnetic radiation on a subwavelength scale, and there is major interest in such devices for a wide variety of applications in photonics, sensing, and imaging. Significant effort has been put into developing highly compact, novel, next-generation light sources, which have great potential in realizing efficient sub-wavelength single photon sources and enhanced biological and chemical sensors. We have developed a number of innovative optical antenna designs including elements of chiral metasurfaces for enabling circularly polarized emission from quantum sources, new designs derived from Radio Frequency (RF) elements for quantum source enhancement and directionality, and nanostructures for investigating plasmonic dark-modes that have the ability to significantly reduce the Q-factor of nano-antennas. A challenge, however, remains the development of a scalable nanofabrication technology. The capacity to mass-produce nano-antennas will have a considerable impact on the commercial viability of these devices, and greatly improve research throughput. Here we present recent progress in the development of scalable fabrication strategies for producing of nano-antennas and antenna arrays, along with slot based plasmonic optical devices.

Indium tin oxide film characterization using the classical Hall Effect

We have used the classical Hall Effect to electrically characterize indium tin oxide (ITO) films grown by two different techniques on silica substrates. ITO films have the unique property that they can be both electrically conducting (and to be used for a gate electrode for example) as well as optically transparent (at least in the visible part of the spectrum). In the near infrared (NIR) the transmission typically reduces. However, the light absorption can in principle be compensated by growing thinner films.

Waveguide coupled MSM photodiode for surface plasmon polariton detection

The requirement of in-plane detection is crucial for large scale plasmonic technology. Metal-semiconductor-metal photodiodes can be used as ultrafast detectors in plasmonic integrated circuits. In this paper we show numerical simulations of the MSM photodiode coupled to a plasmonic waveguide.

Polarisation to colour transformation via nano-antenna enhanced quantum dot emission

Metallic nano-antennas have been shown to be an excellent candidate for enhancing and directing optical emission from semiconductor based quantum dots (QD). QD photoluminescence (PL) enhancement is achieved by placing a suitably orientated QD in the near-field of a resonant metallic nano-antenna. Through the careful design of an optical Vee-antenna, two distinct visible resonances can be obtained, enabling the polarization dependant enhancement of two different QD sources, thus producing a polarization-to-colour transformation at the nano-scale. Possible future applications include an optical nano-scale demultiplexer device.