Boris Desiatov

Locally Oxidized Silicon Surface-Plasmon Schottky Detector for Telecom Regime

We experimentally demonstrate an on-chip nanoscale silicon surface-plasmon Schottky photodetector based on internal photoemission process and operating at telecom wavelengths. The device is fabricated using a self-aligned approach of local-oxidation of silicon (LOCOS) on silicon on insulator substrate, which provides compatibility with standard complementary metal-oxide semiconductor technology and enables the realization of the photodetector and low-loss bus photonic waveguide at the same fabrication step. Additionally, LOCOS technique allows avoiding lateral misalignment between the silicon surface and the metal layer to form a nanoscale Schottky contact. The fabricated devices showed enhanced detection capability for shorter wavelengths that is attributed to increased probability of the internal photoemission process. We found the responsivity of the nanodetector to be 0.25 and 13.3 mA/W for incident optical wavelengths of 1.55 and 1.31 μm, respectively. The presented device can be integrated with other nanophotonic and nanoplasmonic structures for the realization of monolithic opto-electronic circuitry on-chip.

Waveguide based compact silicon Schottky photodetector with enhanced responsivity in the telecom spectral band

We experimentally demonstrate an on-chip compact and simple to fabricate silicon Schottky photodetector for telecom wavelengths operating on the basis of internal photoemission process. The device is realized using CMOS compatible approach of local-oxidation of silicon, which enables the realization of the photodetector and low-loss bus photonic waveguide at the same fabrication step. The photodetector demonstrates enhanced internal responsivity of 12.5mA/W for operation wavelength of 1.55µm corresponding to an internal quantum efficiency of 1%, about two orders of magnitude higher than our previously demonstrated results [22]. We attribute this improved detection efficiency to the presence of surface roughness at the boundary between the materials forming the Schottky contact. The combination of enhanced quantum efficiency together with a simple fabrication process provides a promising platform for the realization of all silicon photodetectors and their integration with other nanophotonic and nanoplasmonic structures towards the construction of monolithic silicon opto-electronic circuitry on-chip.

Experimental demonstration of locally oxidized hybrid silicon-plasmonic waveguide

We experimentally demonstrate a self-aligned approach for the fabrication of nanoscale hybrid silicon-plasmonic waveguide fabricated by local oxidation of silicon (LOCOS). Implementation of the LOCOS technique provides compatibility with standard complementary metal-oxide-semiconductor technology and allows avoiding lateral misalignment between the silicon waveguide and the upper metallic layer. We directly measured the propagation and the coupling loss of the fabricated hybrid waveguide using a near-field scanning optical microscope. The demonstrated structure provides nanoscale confinement of light together with a reasonable propagation length of ∼100u2002μm. As such, it is expected to become an important building block in future on-chip optoelectronic circuitry.

On-Chip Integrated, Silicon–Graphene Plasmonic Schottky Photodetector with High Responsivity and Avalanche Photogain

We report an on-chip integrated metal graphene–silicon plasmonic Schottky photodetector with 85 mA/W responsivity at 1.55 μm and 7% internal quantum efficiency. This is one order of magnitude higher than metal–silicon Schottky photodetectors operated in the same conditions. At a reverse bias of 3 V, we achieve avalanche multiplication, with 0.37A/W responsivity and avalanche photogain ∼2. This paves the way to graphene integrated silicon photonics.

Nanoscale Plasmonic Memristor with Optical Readout Functionality

We experimentally demonstrate for the first time a nanoscale resistive random access memory (RRAM) electronic device integrated with a plasmonic waveguide providing the functionality of optical readout. The device fabrication is based on silicon on insulator CMOS compatible approach of local oxidation of silicon, which enables the realization of RRAM and low optical loss channel photonic waveguide at the same fabrication step. This plasmonic device operates at telecom wavelength of 1.55 μm and can be used to optically read the logic state of a memory by measuring two distinct levels of optical transmission. The experimental characterization of the device shows optical bistable behavior between these levels of transmission in addition to well-defined hysteresis. We attribute the changes in the optical transmission to the creation of a nanoscale absorbing and scattering metallic filament in the amorphous silicon layer, where the plasmonic mode resides.

Nanoscale light–matter interactions in atomic cladding waveguides

Alkali vapours, such as rubidium, are being used extensively in several important fields of research such as slow and stored light nonlinear optics quantum computation, atomic clocks and magnetometers. Recently, there is a growing effort towards miniaturizing traditional centimetre-size vapour cells. Owing to the significant reduction in device dimensions, light–matter interactions are greatly enhanced, enabling new functionalities due to the low power threshold needed for nonlinear interactions. Here, taking advantage of the mature platform of silicon photonics, we construct an efficient and flexible platform for tailored light–vapour interactions on a chip. Specifically, we demonstrate light–matter interactions in an atomic cladding waveguide, consisting of a silicon nitride nano-waveguide core with a rubidium vapour cladding. We observe the efficient interaction of the electromagnetic guided mode with the rubidium cladding and show that due to the high confinement of the optical mode, the rubidium absorption saturates at powers in the nanowatt regime.

Plasmonic V-groove waveguides with Bragg grating filters via nanoimprint lithography

We demonstrate spectral filtering with state-of-the-art Bragg gratings in plasmonic V-groove waveguides fabricated by wafer scale processing based on nanoimprint lithography. Transmission spectra of the devices having 16 grating periods exhibit spectral rejection of the channel plasmon polaritons with 8.2 dB extinction ratio and -3 dB bandwidth of Δλ = 39.9 nm near telecommunications wavelengths. Near-field scanning optical microscopy measurements verify spectral reflection from the grating structures, and the oscillations of propagating modes along grating-less V-grooves correspond well with effective refractive index values calculated by finite element simulations in COMSOL. The results represent advancement towards the implementation of plasmonic V-grooves with greater functional complexity and mass-production compatibility.

Polarization selective beam shaping using nanoscale dielectric metasurfaces

Metasurfaces consisting of ultrathin nanostructures are utilized to control the properties of light including its phase, amplitude and polarization. Hereby, we demonstrate the capability of such structures to perform arbitrary polarization selective beam shaping using dielectric nanoscale metasurfaces implemented in silicon. By illuminating the structure with right handed circular polarization we reconstruct a desired image. When switching the polarization into its orthogonal state, we obtain the reconstruction of a different image. This demonstration shows the potential of using dielectric metasurfaces for high efficiency beam shaping applications in general, and specifically for polarization coded beam shaping.

Plasmonic enhanced silicon pyramids for internal photoemission Schottky detectors in the near-infrared regime

We demonstrate a nanoscale broadband silicon plasmonic Schottky detector with high responsivity and improved signal to noise ratio operating in the sub-bandgap regime. Responsivity is enhanced by the use of pyramidally shaped plasmonic concentrators. Owing to the large cross-section of the pyramid, light is collected from a large area which corresponds to its base, concentrated toward the nano apex of the pyramid, absorbed in the metal, and generates hot electrons. Using the internal photoemission process, these electrons cross over the Schottky barrier and are collected as a photocurrent. The combination of using silicon technology together with the high collection efficiency and nanoscale confinement makes the silicon pyramids ideal for playing a central role in the construction of improved photodetectors. Furthermore, owing to the small active area, the dark current is significantly reduced as compared with flat detectors, and thus an improved signal to noise ratio is obtained. Our measurements show high responsivities over a broad spectral regime, with a record high of about 30xa0mA/W at the wavelength of 1064xa0nm, while keeping the dark current as low as ∼100u2009u2009nA. Finally, such detectors can also be constructed in the form of a pixel array, and thus can be used as focal plane detector arrays.

Plasmonic nanofocusing of light in an integrated silicon photonics platform

The capability to focus electromagnetic energy at the nanoscale plays an important role in nanoscinece and nanotechnology. It allows enhancing light matter interactions at the nanoscale with applications related to nonlinear optics, light emission and light detection. It may also be used for enhancing resolution in microscopy, lithography and optical storage systems. Hereby we propose and experimentally demonstrate the nanoscale focusing of surface plasmons by constructing an integrated plasmonic/photonic on chip nanofocusing device in silicon platform. The device was tested directly by measuring the optical intensity along it using a near-field microscope. We found an order of magnitude enhancement of the intensity at the tips apex. The spot size is estimated to be 50 nm. The demonstrated device may be used as a building block for lab on a chip systems and for enhancing light matter interactions at the apex of the tip.