Kelvin Nanotechnology Ltd.

Glasgow, United Kingdom

Kelvin Nanotechnology Ltd.

Glasgow, United Kingdom
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Slight T.J.,Compound Semiconductor Technologies | Odedina O.,University of Glasgow | Meredith W.,Compound Semiconductor Technologies | Docherty K.E.,Kelvin Nanotechnology Ltd. | Kelly A.E.,University of Glasgow
IEEE Photonics Technology Letters | Year: 2016

We report on the design, fabrication, and characterization of InGaN/GaN distributed feedback laser diodes emitting at a single wavelength around 430 nm. Third-order sidewall-etched gratings were used which have the advantage of a simple fabrication route with no need for overgrowth. We carried out waveguide modeling to find the effective modal indices of the grating and calculate the coupling coefficient. The laser ridge and the grating were formed by electron beam lithography followed by inductively coupled plasma etching. The as-cleaved lasers emitted in the pulsed regime with an SMSR of 22 dB and a peak single-mode output power of 40 mW. Slope efficiency was similar for both Fabry-Perot and DFB chips demonstrating that performance is not compromised by the addition of the grating. © 1989-2012 IEEE.

Agency: European Commission | Branch: FP7 | Program: CP-IP | Phase: NMP.2013.1.4-2 | Award Amount: 12.85M | Year: 2013

The thermal properties of nanostructured materials are of fundamental importance to modern technology, but at present reproducible metrological definitions, tools and methods do not exist. This is because the mechanisms of heat transport at the nanoscale are entirely different to those at the macro scale. The project will place nanothermal metrology on a solid basis by an integrated physics-based experimental and modelling effort to: Define a common terminology for nanothermal measurement Realise standard materials and devices for measurement and calibration of nanothermal measurements Develop new instruments and methods for traceable nanothermal measurement Develop calibrated and validated thermal models covering the range from atomic to macro-scale Apply these tools to selected representative industrial problems Assess the tools for suitability for adoption as potential standards of measurement including their traceability and reproducibility The objectives will be achieved by a team comprising physicists, materials scientists, modellers, instrumentalists, microscopists, industrial partners (including SMEs and OEMs) and National Measurement Institutes. The outputs of QUANTIHEAT will be embodied in highly characterised reference samples, calibration systems, measurement tools, numerical modelling tools, reference measurements and documented procedures. The availability of calibrated numerical modelling tools will facilitate the rapid digital thermal design of new nanosystems without the need for extensive prototyping. Their validation against experiment over all length scales will provide a solid basis for the deployment of new nanostructured materials, devices and structures having optimised performance without the need for excessively conservative design. Standardization is a key driver of industrial and scientific progress: QUANTIHEAT is expected to constitute a de-facto standard for a key area of physical measurement at the nanoscale worldwide.

Cotter J.P.,Imperial College London | Cotter J.P.,University of Vienna | McGilligan J.P.,University of Strathclyde | Griffin P.F.,University of Strathclyde | And 5 more authors.
Applied Physics B: Lasers and Optics | Year: 2016

It has recently been shown that optical reflection gratings fabricated directly into an atom chip provide a simple and effective way to trap and cool substantial clouds of atoms (Nshii et al. in Nat Nanotechnol 8:321–324, 2013; McGilligan et al. in Opt Express 23(7):8948–8959, 2015). In this article, we describe how the gratings are designed and microfabricated and we characterise their optical properties, which determine their effectiveness as a cold atom source. We use simple scalar diffraction theory to understand how the morphology of the gratings determines the power in the diffracted beams. © 2016, The Author(s).

Slight T.J.,Compound Semiconductor Technologies | Odedina O.,University of Glasgow | Meredith W.,Compound Semiconductor Technologies | Docherty K.E.,Kelvin Nanotechnology Ltd | Kelly A.E.,University of Glasgow
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2016

We report on deeply etched sidewall grating DFB lasers in the InGaN/GaN material system emitting at a single wavelength around 434 nm. GaN lasers have a wide range of applications in communications, displays and storage. The availability of a single wavelength device with a good side mode suppression ratio (SMSR) would allow further applications to be addressed such as sources for laser cooling and Fraunhofer line operation for solar background free communications. Sidewall etched gratings have the advantage of fabrication with no need for overgrowth and have been demonstrated in a range of other material systems and wavelengths. Importantly for GaN based devices, this design has the potential to minimise fabrication induced damage to the epi structure. We investigated two laser designs, one with 80 % duty-cycle 3rd order gratings and another with 39th order partial gratings. Simulation of the 2D waveguide sections was carried out to find the optimal grating width. For fabrication, the laser ridge and gratings were patterned in a single step using electron beam lithography and ICP etched to a depth of 500 nm. Contact metal was deposited and the sample thinned and cleaved into 1 mm long cavities. The as-cleaved 3rd order lasers emit in the pulsed regime with a SMSR of 20 dB and a peak single-mode output power of 40 mW. The output power is similar to that of parallel processed FP lasers. The 39th order lasers also exhibit narrow spectral width at an output power of 10 mW. © 2016 SPIE.

Linares P.G.,Technical University of Madrid | Marti A.,Technical University of Madrid | Antolin E.,Technical University of Madrid | Farmer C.D.,Kelvin Nanotechnology Ltd | And 3 more authors.
Solar Energy Materials and Solar Cells | Year: 2012

The intermediate band solar cell (IBSC) is based on a novel photovoltaic concept and has a limiting efficiency of 63.2%, which compares favorably with the 40.7% efficiency of a conventional, single junction solar cell. It is characterized by a material hosting a collection of energy levels within its bandgap, allowing the cell to exploit photons with sub-bandgap energies in a two-step absorption process, thus improving the utilization of the solar spectrum. However, these intermediate levels are often regarded as an inherent source of supplementary recombination, although this harmful effect can in theory be counteracted by the use of concentrated light. We present here a novel, low-temperature characterization technique using concentrated light that reveals how the initially enhanced recombination in the IBSC is reduced so that its open-circuit voltage is completely recovered and reaches that of a conventional solar cell. © 2011 Elsevier B.V. All rights reserved.

Linares P.G.,Technical University of Madrid | Marti A.,Technical University of Madrid | Antolin E.,University of Nottingham | Ramiro I.,Technical University of Madrid | And 4 more authors.
IEEE Journal of Photovoltaics | Year: 2013

In this paper, we describe a novel low-temperature concentrated light characterization technique, and we apply it to the study of the so-called intermediate band solar cell (IBSC). This type of cell is characterized by hosting an intermediate band (IB) that is capable of providing both high current and high voltage. In most of its practical implementations, which are carried out by means of quantum dot (QD) structures, the energy band-diagram shows additional confined energy levels. These extra levels are responsible for an increase in the thermalization rate between the IB and the conduction band, which produces the degradation of the open-circuit voltage VOC. The original implementation of a setup that combines concentrated light and low temperature conditions is discussed in this paper. In this context, photogenerated current (IL)-VOC characteristics that are measured on QD-IBSC are presented in order to study their recombination, as well as their VOC recovery. © 2011-2012 IEEE.

Luque A.,Technical University of Madrid | Linares P.G.,Technical University of Madrid | Antolin E.,Technical University of Madrid | Ramiro I.,Technical University of Madrid | And 5 more authors.
Journal of Applied Physics | Year: 2012

In this paper, a model for intermediate band solar cells is built based on the generally understood physical concepts ruling semiconductor device operation, with special emphasis on the behavior at low temperature. The model is compared to J L-V OC measurements at concentrations up to about 1000 suns and at temperatures down to 20 K, as well as measurements of the radiative recombination obtained from electroluminescence. The agreement is reasonable. It is found that the main reason for the reduction of open circuit voltage is an operational reduction of the bandgap, but this effect disappears at high concentrations or at low temperatures. © 2012 American Institute of Physics.

Thoms S.,University of Glasgow | Macintyre D.S.,University of Glasgow | Docherty K.E.,Kelvin Nanotechnology Ltd. | Weaver J.M.R.,University of Glasgow
Microelectronic Engineering | Year: 2014

Alignment between lithography layers is essential for device fabrication. A minor defect in a single marker can lead to incorrect alignment and this can be the source of wafer reworks. In this paper we show that this can be prevented by using extra alignment markers to check the alignment during patterning, rather than inspecting vernier patterns after the exposure is completed. Accurate vernier patterns can often only be read after pattern transfer has been carried out. We also show that by using a Penrose tile as a marker it is possible to locate the marker to about 1 nm without fully exposing the resist. This means that the marker can be reused with full accuracy, thus improving the layer to layer alignment accuracy. Lithography tool noise limits the process. © 2014 Elsevier B.V. All rights reserved.

Agency: GTR | Branch: Innovate UK | Program: | Phase: Feasibility Study | Award Amount: 162.30K | Year: 2015

Miniaturised, portable chip-scale clocks and sensors are regarded as central priorities for future sensors, navigation and secure communication systems. The Royal Academy of Engineering has highlighted the vulnerability of global navigation satellite systems and recommends that all critical infrastructures relying on accurate time measurements should have a robust holdover alternative technology. This project addresses one of the key components in achieving this goal by implementing DFB laser and PPLN technology developed for consumer applications to produce a cost effective, miniature laser technology platform for achieving short wavelength sources for use in quantum systems and sensors. By utilising technology developed for picoprojector, head up display and near eye display applications we will achieve a step change in laser technologies for quantum applications resulting in a 10e5 reduction in form factor. The vision of this project is to demonstate a scaleable, commercially viable technological approach to prodcuing laser sources for quantum applications building on the partners experience in applying these techniques for consumer applications.

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