There is great interest in aluminum based plasmonic devices due to the relatively high plasma frequency of this material as well as its low cost and self-passivating oxide layer. The passivation layer provides aluminum plasmonics with the long-term stability required for practical applications. While several studies have investigated the impact of this oxide layer on the plasmon resonances of aluminum nanostructures on glass substrates, little is known about the effect of high-refractive index substrates on these resonances. Here we present an investigation of aluminum V-shaped antennas resonant in the visible on a silicon substrate. Through comparison between numerical and experimental results, we show that the aluminium passivation layer has little effect on the antenna resonances by comparing numerical simulations both with and without. We show, however, that inclusion of the native oxide layer of the silicon substrate in numerical models is critical for achieving good agreement with experimental data. Furthermore, we computationally explore the influence of the 1.5 eV interband transition of aluminum on plasmon resonances, and find that its effect on the material properties of the resonant structures results in narrower resonances in the blue part of the spectrum than if it was not present.

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.

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.

Progress in the excitation of `dark-modes' in plasmonic structures is reported. The interaction of vector beams possessing a spatially inhomogeneous polarization profile with plasmonic nanostructures provides an avenue to probe these resonances.

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.

The plasmonic J-pole antenna is the nanoscale version of a radio frequency design, consisting of a half wavelength arm connected to a quarter wavelength feed pair. Here, we report on an optical J-pole antenna that displays both a dipole (1015 nm) and quadrupole resonance (653 nm). The excitation of the quadrupole resonance is optimum at an angle of incidence directly related to the geometry of the antenna, demonstrating the flexibility of the design. The J-pole antenna shows great promise for enhancing and shaping the angular emission pattern of quantum emitters. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4775382]

We discuss progress in the development of asymmetric cross-shaped plasmonic antennas based on resonant nanoscale apertures surrounded by surface corrugations. By tailoring the aperture and the surrounding surface, we show directionality and polarization control of transmitted light.

Optical antennas have garnered much interest from the optics community for their ability to manipulate light below the diffraction limit of conventional optics. This relatively new capability to transform light at a sub-wavelength scale has been applied to quantum source enhancement, infrared detection and solar cell design. This work aims to expand upon the range of optical antennas presented in literature by exploiting the rich array of well-known radio-frequency (RF) antenna designs and applying them to the optical spectral region, for the enhancement of quantum emitters.

We discuss progress in the development of slot antennas based on resonant apertures. We show that simultaneous field enhancement and beaming can be produced.

We report on a plasmonic metamaterial approach to controlling the polarisation state of visible and near infrared (NIR) light.

Here we report on the integration of metallic nanorods with the phase-change material Vanadium Dioxide (VO2). The change in its optical constants that accompanies the VO2 phase transition permits the modulation of the resonant frequencies of these dipoles. This technique will underpin the development of dynamically tunable optical antennas.

We demonstrate a microfluidics-based fluorescence detection device where the filters, source, detector, and electronically controlled valves are embedded into a Polydimethylsiloxane (PDMS)-based microfluidic chip. The device reported here has been specifically designed for chlorophyll a fluorescence sensing in autonomous systems, such as oceanic applications. In contrast to a monolithic approach, the modular approach made the fabrication of this device simpler and cheaper. For fluorescence detection, an InGaN/GaN LED is used as the excitation source to specifically excite chlorophyll a; a metal-dielectric Fabry–Perot filter was used to extinguish out-of-band excitation. A simple Si photodiode is used as detector and provided with a thermally evaporated CdS emission filter to block the excitation source. This filter combination provides an excellent solution to the difficult problem of combining high-rejection excitation and emission filters in an integrated thin-film format. Furthermore, the metal-dielectric filter provides a much broader angular response than a comparable multilayer Bragg mirror, which is a key advantage in the integrated format. We use a novel paraffin wax-based valve design affords low power single-use actuation, between 0.5 and 1 J per actuation and withstands 0.6 bar differential pressure, which provides better performance than its previously reported counterparts. The remote valve-controlled operation of the fluorescence detection system is demonstrated, illustrating the measurement of a chlorophyll a solution, with a detection limit of 340 μM and subsequent valve-controlled flushing of the measurement reservoir.

Erratum: N2-Based Thermal Passivation of Porous Silicon to Achieve Long-Term Optical Stability [Electrochem. Solid-State Lett., 13, H428 (2010)] T. D. James, Meifang Lai, G. Parish, C. A. Musca, and A. J. Keating Microelectronics Research Group, School of Electrical, Electronic, and Computer Engineering, and Sensors and Advanced Instrumentation Laboratory, School of Mechanical Engineering, The University of Western Australia, Crawley, Western Australia 6009, Australia

A technique is presented to create porous silicon (PS) thin films with long-term optical stability when exposed to normal room conditions. This technique requires the thin films to undergo a rapid thermal annealing treatment at a relatively low temperature of 600 degrees C in N-2 atmosphere for 6 min. Annealing at such a low temperature enables the surface passivation of PS via nitridation without causing the excessive roughness and sintering widely observed at higher annealing temperatures. A mechanism similar to the Haber process is proposed to explain the surface nitridation, in which the nitrogen atmosphere interacts with the as-anodized hydrogen surface species. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3489075] All rights reserved.

A technique is presented for the passivation of porous silicon (PS) thin films via nitrogen based annealing at the lowest temperature ever reported. Annealing freshly anodized PS thin films at temperatures as low as 520 degrees C under N-2 flow in a rapid thermal annealer produces films that show no change in refractive index when exposed to ambient conditions over 60 days. These films also exhibited chemical resistance by surviving a brief dip in both concentrated KOH and buffered HF. Unlike most other PS surface passivation methods, this technique causes negligible reduction in refractive index of the annealed PS thin films. Passivation only occurs when dangling bonds and mono-hydrides populate the PS surface, providing a path for thermal interactions with the N-2 gas. (C) 2009 Elsevier Ltd. All rights reserved.

The production of high quality optical devices based on porous silicon relies on having precise control over the refractive index and thickness of each porous silicon layer. Until now this has been achieved by pre-calibrating each growth system and making sure that parameters such as wafer doping, electrolyte concentration and temperature are kept constant with each fabrication. However low doped silicon required for IR based silicon photonics has significant non-uniformity in the index and growth rate during formation of the porous silicon. The solution we have developed is based on realtime in-situ monitoring of low-doped silicon during porous silicon growth. This process rapidly measures the optical interference between the porous silicon film and the backside silicon surface. The optical light source comes from six coarse-wavelength-division-multiplexed lasers, with rapid switching between wavelengths achieved using a microelectromechanical switch. The system permits rapid measurement (<1 sec) of the reflection spectra from all lasers, enabling real-time thickness and refractive index of each layer to be determined during growth. Our aim is to enable growth of high quality multi-layer films such as those required for Bragg Reflectors and high-Q Fabry-Perot microcavities. In this paper we briefly describe the instrument, the numerical models developed to gather the measurements, and show preliminary results gathered from this instrument during growth. The results show a good agreement with theoretical optical modelling, and also direct measurements of the porous silicon layers.

A method is presented for the preparation of double-sided porous silicon (pSi) wafers using a conductive elastomer electrode. The technique enables the fabrication of laterally highly uniform layers of pSi, and the creation of transmissive pSi-based optical components. The use of the conductive elastomer requires no pre- or postprocessing of the silicon starting wafer. The method demonstrates high reproducibility when the two pSi layers are formed under identical experimental conditions, exhibiting differences in pSi film thickness between the front and back side of < 2% over a 254 nm thick pSi film. (c) 2007 The Electrochemical Society.

A method to determine porous silicon index and thickness during growth is proposed. An rms accuracy of 0.3 and 80 nm for the index and thickness, respectively was estimated based on a synthetic reflectance model including intensity and thermal noise.

The aim of this work was to develop an alignment technique to be used in the production of long, deep, large area microchannel devices. The microchannel design specifications used for the investigation were 800 mu m deep channels of 100 mu m width, with a 200 mu m pitch, over an area of 40 mm x 40 mm. The device was fabricated with (110) orientated silicon, to take advantage of the large wet etch ratio between the {110} and {111} planes. Silicon nitride was used as the channel etchant mask, and was patterned by reactive ion etching. The channels were wet etched in a KOH 40 wt% solution at 80 degrees C to minimize undercut of the silicon nitride mask, while maintaining a reasonable etch rate of 2 mu m min(-1). The {111} crystal plane normal to the {110} wafer surface needed to be determined with high accuracy for the fabrication of microchannels of such a large size. Investigations of several established alignment techniques revealed only one suitable technique: the use of a wet etched alignment feature that is self-aligned to the {111} crystal planes. This resulted in an silicon nitride mask undercut of 10 mu m for channels 800 mu m deep and 45 mm in length.

Nano-porous silicon is investigated as antireflection coating for silicon microlenses. The effect of non-planar silicon surfaces on nano-porous silicon thin film uniformity is examined. V-groves were micromachined in [100] orientated silicon and subsequently anodised in a HF solution to produce nano-porous silicon. The results show for nano-porous silicon fabricated on heavily doped p-type material the electric field has a negligible effect on the uniformity. The orientation of the anodised crystal planes does affect both the nano-porous silicon morphology and anodisation rate. A high quality nano-porous silicon antireflection coating on a planar surface is also demonstrated.