Photonic–Plasmonic Coupling of GaAs Single Nanowires to Optical Nanoantennas (original) (raw)

Optimizing plasmonic nanoantennas via coordinated multiple coupling OPEN

Plasmonic nanoantennas, which can efficiently convert light from free space into sub-wavelength scale with the local field enhancement, are fundamental building blocks for nanophotonic systems. Predominant design methods, which exploit a single type of near-or far-field coupling in pairs or arrays of plasmonic nanostructures, have limited the tunability of spectral response and the local field enhancement. To overcome this limit, we are developing a general strategy towards exploiting the coordinated effects of multiple coupling. Using Au bowtie nanoantenna arrays with metalinsulator-metal configuration as examples, we numerically demonstrate that coordinated design and implementation of various optical coupling effects leads to both the increased tunability in the spectral response and the significantly enhanced electromagnetic field. Furthermore, we design and analyze a refractive index sensor with an ultra-high figure-of-merit (254), a high signal-to-noise ratio and a wide working range of refractive indices, and a narrow-band near-infrared plasmonic absorber with 100% absorption efficiency, high quality factor of up to 114 and a wide range of tunable wavelength from 800 nm to 1,500 nm. The plasmonic nanoantennas that exploit coordinated multiple coupling will benefit a broad range of applications, including label-free bio-chemical detection, reflective filter, optical trapping, hot-electron generation, and heat-assisted magnetic recording.

Engineering light absorption in semiconductor nanowire devices

nmat, 2009

The use of quantum and photon confinement has enabled a true revolution in the development of high-performance semiconductor materials and devices 1-3. Harnessing these powerful physical effects relies on an ability to design and fashion structures at length scales comparable to the wavelength of electrons (∼1 nm) or photons (∼1 µm). Unfortunately, many practical optoelectronic devices exhibit intermediate sizes 4,5 where resonant enhancement effects seem to be insignificant. Here, we show that leaky-mode resonances, which can gently confine light within subwavelength, high-refractive-index semiconductor nanostructures, are ideally suited to enhance and spectrally engineer light absorption in this important size regime. This is illustrated with a series of individual germa-nium nanowire photodetectors. This notion, together with the ever-increasing control over nanostructure synthesis opens up tremendous opportunities for the realization of a wide range of high-performance, nanowire-based optoelectronic devices, including solar cells 6-8 , photodetectors 9-13 , optical modulators 14 and light sources 14,15. Whereas dielectric and metallic cavities both offer strong light confinement, their distinct materials properties translate into markedly different behaviour and applications. Metallic nanos-tructures have recently gained significant attention owing to their unparalleled ability to concentrate light into deep-subwavelength volumes 16,17. This property is derived from the unique optical behaviour of metals that enables collective electron excitations, known as surface plasmons 18. Many exciting plasmonics concepts have emerged, but their application is limited in extent owing to the lossy nature of metals; heat is always generated when light is manipulated by them. In contrast, high-confinement dielectric resonators offer low optical losses but their size is limited to wavelength-scale or larger dimensions by the fundamental laws of diffraction. Interestingly , strong optical resonance effects have been observed in the elastic scattering 19 , extinction 20 , light emission 21 and Raman 22 measurements on deep-subwavelength dielectric spheres and nanowires near natural frequencies of oscillation. These experiments have primarily been far-field measurements, in which the illumination source and detector are located at a substantial distance from the object under study. Here, we point out the possibility to engineer resonant field enhancements inside semiconductor nanowires to tune their spectral absorption features for device applications. We also use the framework of leaky-mode resonances (LMRs) that was originally developed for micrometre-scale resonators to provide an intuitive vantage point from which to understand and engineer these resonant effects in nanoscale structures. To illustrate these concepts and their importance, we directly probe the field enhancements in a set of individual germanium nanowires through

Nanoantennas for visible and infrared radiation

Arxiv preprint arXiv:1103.1568, 2011

Nanoantennas for visible and infrared radiation can strongly enhance the interaction of light with nanoscale matter by their ability to efficiently link propagating and spatially localized optical fields. This ability unlocks an enormous potential for applications ranging from nanoscale optical microscopy and spectroscopy over solar energy conversion, integrated optical nanocircuitry, opto-electronics and density-ofstates engineering to ultra-sensing as well as enhancement of optical nonlinearities.

Resonant Plasmonic and Vibrational Coupling in a Tailored Nanoantenna for Infrared Detection

Physical Review Letters, 2008

A novel resonant mechanism involving the interference of a broadband plasmon with the narrowband vibration from molecules is presented. With the use of this concept, we demonstrate experimentally the enormous enhancement of the vibrational signals from less than one attomol of molecules on individual gold nanowires, tailored to act as plasmonic nanoantennas in the infrared. By detuning the resonance via a change in the antenna length, a Fano-type behavior of the spectral signal is observed, which is clearly supported by full electrodynamical calculations. This resonant mechanism can be a new paradigm for sensitive infrared identification of molecular groups.

Toward Plasmonics with Nanometer Precision: Nonlinear Optics of Helium-Ion Milled Gold Nanoantennas

Nano Letters, 2014

Plasmonic nanoantennas are versatile tools for coherently controlling and directing light on the nanoscale. For these antennas, current fabrication techniques such as electron beam lithography (EBL) or focused ion beam (FIB) milling with Ga + -ions routinely achieve feature sizes in the 10 nm range. However, they suffer increasingly from inherent limitations when a precision of single nanometers down to atomic length scales is required, where exciting quantum mechanical effects are expected to affect the nanoantenna optics. Here, we demonstrate that a combined approach of Ga + -FIB and milling-based He + -ion lithography (HIL) for the fabrication of nanoantennas offers to readily overcome some of these limitations. Gold bowtie antennas with 6 nm gap size were fabricated with single-nanometer accuracy and high reproducibility. Using third harmonic (TH) spectroscopy, we find a substantial enhancement of the nonlinear emission intensity of single HIL-antennas compared to those produced by state-of-the-art gallium-based milling. Moreover, HIL-antennas show a vastly improved polarization contrast. This superior nonlinear performance of HIL-derived plasmonic structures is an excellent testimonial to the application of He + -ion beam milling for ultrahigh precision nanofabrication, which in turn can be viewed as a stepping stone to mastering quantum optical investigations in the near-field. P lasmonic nanostructures like metallic nanoantennas have been widely recognized as functional elements in a wide range of applications. Their intense evanescent fields are employed in the generation of femtosecond electron 1,2 or extreme UV atomic line emission. The accompanying tight spatial localization of the near-field is routinely used in singlemolecule spectroscopy, 4−7 near-field or nanoscale imaging, and photovoltaic applications. 10,11 Increasingly, plasmonic nanoantennas also attract attention in the context of quantum mechanical phenomena, however, which require delicate spatial alignment of field or material structures. 12 Consequently, the dependencies of linear and nonlinear optical properties of metallic nanoantennas on size and shape have been investigated extensively in the recent years. 13−16 A particular focus has been on so-called gap plasmons, which appear in the nanometer-sized void between two plasmonic antennas. These have been demonstrated to provide tremendous enhancement of the local electric field in the gap, thanks to the growth of near-field-mediated optical interactions. 18−20 Aiming for such enhanced optical near fields in nanoantenna structures, reproducible and precise fabrication techniques are indispensable.

Doubly and Triply Coupled Nanowire Antennas

The Journal of Physical Chemistry C, 2012

Nanoantenna is one of the most important optical components for light harvesting. In this study, we show experimental evidence of interactions between coupled nanowires by comparing the fluorescence properties of quantum dots on single nanowire as well as doubly and triply coupled nanowire arrays. Because of the localized surface plasmon mode, there are strong polarization dependences in this photon−plasmon−exciton conversion process. It is interesting that both the polarizationdependent enhancement and the degree of fluorescence polarization are more pronounced for triply coupled nanowires than that of doubly coupled nanowire, while the case of single nanowire is weakest. Our theoretical analysis indicates the above phenomena can be ascribed to the coupled plasmon from the nanowire antennas. Our investigations demonstrate a potential method to control the polarization of emitters using coupled nanowire arrays.

Biased Nanoscale Contact as Active Element for Electrically Driven Plasmonic Nanoantenna

ACS Photonics, 2017

Electrically-driven optical antennas can serve as compact sources of electromagnetic radiation operating at optical frequencies. In the most widely explored configurations, the radiation is generated by electrons tunneling between metallic parts of the structure when a bias voltage is applied across the tunneling gap. Rather than relying on an inherently inefficient inelastic light emission in the gap, we suggest to use a ballistic nanoconstriction as the feed element of an optical antenna supporting plasmonic modes. We discuss the underlying mechanisms responsible for the optical emission, and show that with such a nanoscale contact, one can reach quantum efficiency orders of magnitude larger than with standard light-emitting tunneling structures.

Enabling High Efficiency Nanoplasmonics with Novel Nanoantenna Architectures

Scientific reports, 2015

Surface plasmon polaritons (SPPs) are propagating excitations that arise from coupling of light with collective electron oscillations. Characterized by high field intensity and nanometric dimensions, SPPs fashion rapid expansion of interest from fundamental and applicative perspectives. However, high metallic losses at optical frequencies still make nanoplasmonics impractical when high absolute efficiency is paramount, with major challenge is efficient plasmon generation in deep nanoscale. Here we introduce the Plantenna, the first reported nanodevice with the potential of addressing these limitations utilizing novel plasmonic architecture. The Plantenna has simple 2D structure, ultracompact dimensions and is fabricated on Silicon chip for future CMOS integration. We design the Plantenna to feed channel (20 nm × 20 nm) nanoplasmonic waveguides, achieving 52% coupling efficiency with Plantenna dimensions of λ(3)/17,000. We theoretically and experimentally show that the Plantenna enor...