A nonlinear plasmonic antenna switch as building block for ultracompact photonic devices.

Lead Research Organisation: University of Southampton
Department Name: School of Physics and Astronomy


Active control over light on nanometer length scales holds promise for many applications in modern science and technology, ranging from optical telecommunication to coherent quantum information. In this First Grant we will develop a new class of ultracompact photonic devices based on nanoscale plasmonic antennas. Plasmonics, the science dealing with confining light at the surface of metals, has the potential to become one of the key nanotechnologies capable of combining electric and photonic components on a single chip. Photonic integration is important to achieve medium-range information transfer and chip-to-chip interconnects in next-generation communication networks.Analogous to their radiowave counterparts, plasmonic nanoantennas are ideal structures for matching incident optical radiation to a nanoscale volume. We propose that the small footprint and ultrafast response of a single antenna can be used to design a new type of ultrafast optical transistor. We introduce here a novel design of an antenna optical switch capable of producing a large modulation depth and requiring only a fraction of the optical power used in state-of-the-art microphotonic switches. In the first part of the project we will demonstrate the proof-of-principle of antenna switching. In the second part, we will integrate a nanoantenna onto a silicon photonic waveguide. We will use the antenna to control the transmission of the photonic waveguide using its very strong scattering at the resonant plasmon wavelength. During our experiments we will work together with a UK fiber-laser company in optimizing a new light source for single-nanoantenna ultrafast spectroscopy.As a follow-on to this project, we will explore the use of antenna switches as saturable absorber medium in a novel class of ultrafast semiconductor lasers. For this we build on the very strong expertise already present in Southampton on semiconductor lasers. The proposed research programme will combine fundamental scientific research with novel technological applications, bringing together yet unconnected fields of research. Successes will benefit to a new generation of light-driven information technology and to low-cost ultrafast lasers for use in applications like biosensing and terahertz generation. Although the initial research will be at a fundamental level, its results will have a large application perspective, with potential benefits to the UK photonics industry.

Planned Impact

The research presented in this proposal is aimed at integration of plasmonic nanoantennas in new technologically important areas such as silicon photonics and ultrafast semiconductor lasers. The work package combines fundamental research with a strong application perspective. We expect this approach to generate considerable impact in society, which will be actively pursued in various strong collaborations planned in this project. Both the areas of plasmonics and microphotonics have a considerable demonstrated positive impact on society. Examples that have improved the quality of life are plasmonic biosensors used in clinical environments and optical telecommunication which has powered broadband data-communication and internet. The unique features of the proposed nanoantenna switches will allow the design of novel nanoscale optical devices. In particular, we will explore the use of antennas to control the flow of light in silicon integrated photonic circuits. Silicon photonics holds enormous technological potential as a novel platform for optical information technology. It is expected to result in new and improved functionalities compared to existing fiber communication technology. Development of silicon photonics has a large industrial support base worldwide including Intel, IBM, Kotura, and in the UK, Bookham and QinetQ. Our programme on nanoantennas has the potential to contribute to establishing a toolkit of components for a viable silicon photonics technology. Antenna switches specifically can be applicable as broadband directional couplers, ultrafast broadband switches, and tunable frequency filters.In the follow-up research we will investigate the functionality of antenna switches as saturable absorber in ultrafast semiconductor lasers. This research will have very important potential applications; a low-cost compact femtosecond laser would be of great benefit for many applications of ultrafast technology, including compact biomedical sensors and terahertz generation for security applications. In the transfer of our results, we will be able to benefit from the excellent connections with relevant industrial and scientific beneficiaries already available in the groups of Prof. Reed and Prof. Tropper. As an example of our commitment in actively seeking interaction with industry we emphasize the collaboration with small-scale technology company Fianium in this project. The integrated fiber solution which we will develop as part of our project may find practical use for example in biomedical imaging and nondestructive materials testing. Impact in the academic environment will primarily take place through scientific publications and presentations at national and international scientific meetings. Integration of antennas with silicon photonics will contribute to a relatively young research area where very little explorations have been made so far. Successes in integrating these research areas will lead to a strong synergy and increased momentum. The collaboration between the PI and the Silicon Photonics team lead by Prof. Reed will be able to gain visibility in the community as Prof. Reed is currently leading a large UK-wide consortium. Impact on people will take place through the PI's interactions with PhD and undergraduate students based on his position as a lecturer. Although no graduate student is directly associated to this research project, members of the PI's research team will be able to benefit from its progress, through interactions in the lab and during work discussions. Final-year undergraduate (MPhys) students will be working along with the PI's research team as part of their educational training. Other contributions to student education are made in the form of summer studentships, for which the PI has already secured two bursaries for the year 2009.
Description In this project, we have investigated hybrid nanosystems consisting of a metallic nanostructure and a nonmetallic 'active' medium. Similar to radiowave antennas used to transmit and receive information, the metallic nanostructures act as antennas for visibile and near-infrared light. Our aim was to develop hybrid devices where the antenna properties could be controlled using an external optical pulse.

Our main findings are:

1. We have developed a proof-of-principle demonstration of a new type of conductively-loaded nanoantenna, where the antenna can be switched between a capacitive and a conductive state by controlling a nanometer-sized gap between the two antenna arms. This design has been shown to be favourable for use as optical transistor, because of its low switching energy per bit, small footprint, and potentially large modulation contrast in both the far-field and the near-field response.

2. Experimentally, we have demonstrated strong optical modulation of hybrid structures consisting of a gold nanoantenna on top of the transparent conductive material indium-tin-oxide (ITO). We have shown that the antenna acts as a sensitizer for the ITO; fast local heat injection by the antenna results in large variation of the free-electron density and a resulting strong change in the refractive index.

3. We have demonstrated that this hybrid modulation occurs in a variety of systems, where we studied antennas fabricated using a new method of colloidal nanosphere lithography. In addition, we investigated different deposition methods for the ITO and have done the first preliminary studies of aluminium-doped zinc oxide (AZO) deposited by Atomic Layer Deposition (ALD). The ALD method results in layers of improved quality compared to sputtering, which is of importance to obtain devices with reproducible characteristics.

4. In our experiments we have made use of a custom-built laser system, which was provided by Southampton spin-off company Fianium. We have shown that it is possible to use this system for picosecond pump-probe experiments where the probe light could be tuned over a wide range in the visible and near-infrared. Our work has contributed to the adoption of supercontinuum fibre lasers into new nanophotonics applications.
Exploitation Route Photonics is finding its way into everyday life through broadband internet, optical storage, and next-generation information devices. Nanoscale optical elements based on antenna hybrids are still at an early stage in their development but it is anticipated that they will form an important building block for next-generation devices in a 5-10 year timeframe. Currently we are continuing research on the development of plasmonic nanoantenna transistor devices. As a direct potential application we are considering the use of nanoantennas in saturable absorbers for modelocked semiconductor lasers. For this we are collaborating with a group in Southampton working on VECSELs, which has direct links with laser companies. We expect to deliver first demonstrators on this technology within the next 1-2 years.

Ultimately, we aim to develop a fast nanoantenna transistor which can be used for on-chip routing of optical information. This requires an additional 3-5 years of development which is currently supported by an EPSRC grant. We expect that such a prototype antenna transistor will find disruptive new applications in ultracompact integrated optical switching devices.
Sectors Digital/Communication/Information Technologies (including Software)

URL http://nanotechweb.org/cws/article/tech/46020
Description Societal impact has been generated through training of postgraduate researchers and through associated undergraduate research projects. As this is a First Grant, the scope was limited and mainly aimed at launching the PI's activity following up into Grant EP/J011797/1. Impacts include active collaboration grants with DSTL and Centre for Defense Enterprise in development of new sensor technology.
First Year Of Impact 2011
Sector Aerospace, Defence and Marine,Digital/Communication/Information Technologies (including Software)
Impact Types Societal

Description Collaboration with San Sebastian, Spain 
Organisation Spanish National Research Council (CSIC)
Country Spain 
Sector Public 
PI Contribution 1 month hosting of PDRA from Spain Pablo Albella in Southampton, February 2012
Collaborator Contribution PDRA researcher time for theoretical / computational support of research activity
Impact N. Large, M. Abb, J. Aizpurua, O. L. Muskens, Photoconductively loaded plasmonic nanoantenna as building block for ultracompact optical switches, Nano Lett. 10, 1741 - 1746 (2010) M. Abb, P. Albella, J. Aizpurua, O. L. Muskens, All-optical control of a single plasmonic nanoantenna-ITO hybrid, Nano Lett. 11(6), 2457-2463 (2011) M. Abb, Y. Wang, P. Albella, C. H. de Groot, J. Aizpurua, and O. L. Muskens, Interference, Coupling, and Nonlinear Control of High-Order Modes in Single Asymmetric Nanoantennas, ACS Nano 6 (7), 6462-6470 (2012) Y. Wang, M. Abb, S. A. Boden, J. Aizpurua, C. H. de Groot, O. L. Muskens, Ultrafast nonlinear control of progressively loaded, single plasmonic nanoantennas fabricated using helium ion milling, Nano Lett. 13, 5647-5653 (2013)
Start Year 2010