Ofir Sorias

Plasmonic Nanoantennas for Broad-Band Enhancement of Two-Photon Emission from Semiconductors

We demonstrate experimentally and theoretically a broad-band enhancement of the spontaneous two-photon emission from AlGaAs at room temperature by plasmonic nanoantenna arrays fabricated on the semiconductor surface. Plasmonic structures with inherently low quality factors but very small effective volumes are shown to be optimal. A 20-fold enhancement was achieved for the entire antenna array, corresponding to an enhancement of nearly 3 orders of magnitude for charge carriers emitting at the near field of a plasmonic antenna.

First demonstration of plasmonic GaN quantum cascade detectors with enhanced efficiency at normal incidence

We have designed, fabricated and measured the first plasmon-assisted normal incidence GaN/AlN quantum cascade detector (QCD) making use of the surface plasmon resonance of a two-dimensional nanohole Au array integrated on top of the detector absorption region. The spectral response of the detector at room temperature is peaked at the plasmon resonance of 1.82 μm. We show that the presence of the nanohole array induces an absolute enhancement of the responsivity by a factor of ~30 over that of the bare device at normal incidence and by a factor of 3 with respect to illumination by the 45° polished side facet. We show that this significant improvement arises from two phenomena, namely, the polarization rotation of the impinging light from tangential to normal induced by the plasmonic structure and from the enhancement of the absorption cross-section per quantum well due to the near-field optical intensity of the plasmonic wave.

Doubly Resonant Nanoantennas on Diamond for Spatial Addressing of Spin States

The negatively charged nitrogen-vacancy (NV) color center in diamond is an important atom-like system for emergent quantum technologies and sensing at room temperature. The light emission rates and collection efficiency are key issues toward realizing NV-based quantum devices. In that aspect, we propose and experimentally demonstrate a selective and spatially localized method for enhancing the light-matter interaction of shallow NV centers in bulk diamonds. This was achieved by polarized doubly resonant plasmonic antennas, tuned to the NV phonon sideband transition peak in the red and the narrowband near infrared (NIR) singlet transition. We obtained a photoluminescence (PL) enhancement factor of about 10 from NV centers within the hot spot of the antenna area (excluding the extraction efficiency enhancement) and similar emission lifetime reduction. The functionality of the double resonance antenna is controlled by the impinging light polarization.

Responsivity Enhancement of Metal-Insulator-Semiconductor Photodetectors on Silicon-on-Insulator Substrates by Plasmonic Nanoantennas

We report metal-insulator-semiconductor photodetectors fabricated on a silicon-on-insulator substrate, exhibiting an enhanced responsivity in the near-infrared due to the incorporation of Au-nanoantennas at the optical input port. The optimal antenna design and the photoresponse enhancements have been calculated using detailed finite-difference time-domain simulations. These nanoantennas modify the propagation of the input optical signals. In this regime, strong plasmonic local field enhancements are observed. The maximum responsivity enhancement, 40%, was obtained at 780 nm; while at wavelengths shorter than 720 nm, the responsivity is reduced due to absorption losses in the Au-nanoantennas.

Epitaxial Nanoflag Photonics: Semiconductor Nanoemitters Grown with Their Nanoantennas

Semiconductor nanostructures are desirable for electronics, photonics, quantum circuitry, and energy conversion applications as well as for fundamental science. In photonics, optical nanoantennas mediate the large size difference between photons and semiconductor nanoemitters or detectors and hence are instrumental for exhibiting high efficiency. In this work we present epitaxially grown InP nanoflags as optically active nanostructures encapsulating the desired characteristics of a photonic emitter and an efficient epitaxial nanoantenna. We experimentally characterize the polarized and directional emission of the nanoflag-antenna and show the control of these properties by means of structure, dimensions, and constituents. We analyze field enhancement and light extraction by the semiconductor nanoflag antenna, which yield comparable values to enhancement factors of metallic plasmonic antennas. We incorporated quantum emitters within the nanoflag structure and characterized their emission properties. Merging of active nanoemitters with nanoantennas at a single growth process enables a new class of devices to be used in nanophotonics applications.

Responsivity enhancement of MIS photodetectors on SOI substrates by plasmonic nanoantennas

We report MIS photodetectors fabricated on a SOI substrate in a CMOS-compatible process, exhibiting an enhanced responsivity in the near-infrared (NIR) due to the incorporation of Au-nanoantennas at the optical input port. These nanoantennas modify the propagation of the input optical signals, serving as an effective anti-reflection coating in the NIR wavelength range. The optimal antenna design and the photo-response enhancements have been calculated using detailed FDTD simulations. The maximum responsivity enhancement, 40%, was obtained at 780 nm, while at wavelengths shorter than 720 nm, responsivity is reduced due to absorption losses in the Au-nanoantennas.

Rosette nano antennas: Light enhancement with high spatial uniformity, multiple resonances and polarization insensitivity

We propose and measure a novel structure denoted Rosette nanoantenna. Spectral and polarization control of the enhanced field is achieved within relatively large uniform area. Applications for light matter interactions and nanophotonics devices are discussed.

Broadband Enhancement of Two-Photon Emission from Semiconductors by Plasmonic Nano-Antennas

We demonstrate experimentally and theoretically a broadband enhancement of the spontaneous two-photon emission from AlGaAs by plasmonic nano-antennas. Plasmonic structures with inherently low quality-factors but very small effective volumes are shown to be optimal.