Tapered Semiconductor Fibres for Nonlinear Photonics Applications

Lead Research Organisation: University of Southampton
Department Name: Optoelectronics Research Ctr (closed)

Abstract

Semiconductor photonics is a field that is currently revolutionizing the future of modern optoelectronic devices. Although semiconductor materials are more commonly associated with electronic functionality (e.g., popular gadgets that use semiconductor microelectronic processors include cell phones, computers, and digital radios), to date a number of important photonic devices have been demonstrated using planar based substrates on a chip including silicon lasers and germanium photodetectors. More recently, however, the incorporation of semiconductor materials into the core of optical fibres has generated much interest as it provides a unique opportunity to completely integrate this technology with existing silica fibre infrastructures used in data transmission networks. Fiberized semiconductor devices offer some notable advantages over those developed on-chip such as simple, low cost fabrication (i.e., no need for multimillion dollar cleanroom based lithography) and robust and versatile waveguide geometries. Furthermore, the wide (visible to far-infrared) optical transparency of the semiconductor materials that can be incorporated into the fibre geometry ensures that their applications will extend far beyond optical communications to disciplines such as medicine, sensing, spectroscopy and security monitoring.

The work described in this proposal seeks to combine this exciting new semiconductor fibre platform with a key waveguide technology: tapered optical fibres. Conventional tapered silica fibres, which have varying waveguide dimensions along the length, have been exploited for a wealth of applications such as, optical signal processing, supercontinuum generation, remote sensing, as well as for optimized mode coupling between devices. The extension of these structures to incorporate semiconductor materials with rich optoelectronic functionality into the tapered cores will present new degrees of design flexibility for the optimization of semiconductor optical waveguides. The primary goal of this work will thus be to develop the procedures for the fabrication of high quality tapered semiconductor fibre structures and to demonstrate their potential for nonlinear photonic applications. This highly innovative project has the potential to lead to the development of a number of technologically disruptive all-fibre optoelectronic devices, for example, ultra-compact broadband mid-infrared laser sources for healthcare, frequency combs for chemical analysis, and highly nonlinear optical couplers and switches for ultrafast telecommunications.

Planned Impact

This proposal seeks to develop the procedures for the fabrication of a new class of tapered semiconductor fibre structures and to demonstrate their use for nonlinear photonic applications. The success of this project will thus be measured via the development of technologically disruptive all-fibre optoelectronic devices. We have identified two areas within the EPSRC key research themes, namely information technology and healthcare, which will benefit significantly from these outcomes eventually leading to substantial economic and societal impact.

Within the proposed body of work we have described a number of nonlinear optical processes that could be used to develop devices which have the potential to increase the speed and capacity of data transmission rates, for example, switches, couplers and signal regenerators. These all-fibre integrated devices not only circumvent the complex coupling optics required to link between transport fibres and semiconductor processing chips, but the all-optical signal processing techniques on which they are based will also negate the need to convert between optical and electronic signals which is slow, costly and energy inefficient. Improved energy efficiency in data processing is essential if transfer rates are to continue to increase at the current level to reduce the load on electricity production, and thus the carbon footprint of communication networks. This aspect of "Green Photonics" could also have a significant impact on the environment, since currently ICT is responsible for 2% of global carbon emissions (equivalent to that of the aviation industry) and is expected to grow sharply in the future. Furthermore, we also expect that the tapered waveguide designs will be applicable for future developments in silicon devices on-chip, which are currently the subject of extensive research within some of the world's leading technological companies, including Intel, IBM and Luxtera. Leveraging off the multibillion-dollar silicon based electronics platform, silicon photonics is itself predicted to be a billion-dollar industry by 2020. The beneficiaries of these device developments will largely be information and communications companies and their consumers, who comprise much of the world's population.

The development of compact and inexpensive mid-infrared laser sources will also be of use for the telecommunications industry owing to the need for ultra-broadband systems to mitigate the looming data capacity crunch. In this wavelength regime, the extension to semiconductor fibre core materials is an important advance as for wavelengths >2um standard silica based fibres suffer from high losses. Examples of nonlinear processes that could lead to increased bandwidths include parametric wavelength conversion and mid-infrared Raman amplifiers. In addition, we anticipate that these sources will have a valuable societal impact through their employment in biological and medical applications. Specifically we have identified mid-infrared broadband supercontinuum sources for use in tissue imaging and analysis, and frequency comb generators for spectroscopy (used in disease diagnosis and for drug analysis). In the near term this research is most likely to benefit medical researchers, though we expect that longer term beneficiaries will include healthcare practitioners and patients.

As a research field, semiconductor fibre photonics is still very much in its infancy and, as such, it is difficult to predict all of the potential areas of impact. By training new staff in this area we will ensure that the UK has a solid skill and knowledge base for any future industrial and academic developments. The Optoelectronics Research Centre has a large network of industrial collaborators and so is well placed to ensure that the relevant industrial beneficiaries will hear about our research.
 
Description The key aim of this proposal was to combine two important and highly topical optical technologies; optical fibre tapers and semiconductor functionalized fibres. As of to date we have designed and fabricated a number of different tapered silicon fibre structures, and demonstrated their use for nonlinear optical applications. In particular, we have developed a new technique to fabricate long tapered structures, several centimeters in length, using minimal starting material - significantly reducing fabrication costs. Using the small core fibres that have been fabricated, we have demonstrated various all-optical signal processing functions such as modulation and switching, and more recently, this was extended to broadband supercontinuum generation covering wavelengths from the telecoms band up to the mid-infrared. The potential applications of this work include long wavelength communications, sensing and spectroscopy. Furthermore, using the fibres as resonators we have provided the first demonstration of ultra-low power, ultrafast all-optical switching, which could be employed in future energy efficient networks. Finally, we have been working on ways to grow single crystal materials inside the fibres through a laser crystallization technique. Using this method we have grown the longest, large aspect ratio crystalline silicon wires, and also shown that we can use this method to strain engineer the optical properties of the material. This is particularly significant as it opens up the possibility to use a single silicon core fibre for the generation, modulation and detection of light, key functions in all-optical networks.
Exploitation Route The optical work in our grant could be of use within a number of disciplines. Firstly, the ultrafast signal processing aspects could be employed within information and data communication systems. Secondly, we have recently developed a mid-infrared supercontinuum source using a tapered silicon fibre that can produce several milliwatts of usable power, which is sufficient for many practical spectroscopy and medical applications.

The materials processing aspects developed could also be exploited my more traditional silicon photonics wafer based platforms.
Sectors Digital/Communication/Information Technologies (including Software)

Electronics

Environment

Healthcare

 
Description The development of efficient tapering procedures to produce low loss fibres with transmission properties tailored for specific device applications has transformed the practicability of the silicon fibre platform. This procedure is now employed to produce all our current device demonstrators, which have been exploited for use across the telecommunications band for signal processing, and extending up to the mid-infrared where the applications include sensing and healthcare. This has helped us to expand our academic collaborators, so that we now work with a number of leading silicon core fibre fabrication teams as well as with various end users of the devices.
First Year Of Impact 2015
Sector Digital/Communication/Information Technologies (including Software)
Impact Types Societal

 
Description EPSRC Research Fellowship
Amount £1,150,136 (GBP)
Funding ID EP/P000940/1 
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Public
Country United Kingdom
Start 02/2017 
End 02/2022
 
Title Data for research on modulation in a hybrid silica-silicon microspherical resonator 
Description Data for research published in the paper: Kerr nonlinear switching in a hybrid silica-silicon microspherical resonator 
Type Of Material Database/Collection of data 
Year Produced 2015 
Provided To Others? Yes  
Impact None yet 
 
Title TPA modulation in Ge waveguides 
Description Presents data for research in the paper:Two-photon absorption and all-optical modulation in germanium-on-silicon waveguides for the mid-infrared 
Type Of Material Database/Collection of data 
Year Produced 2015 
Provided To Others? Yes  
Impact None yet 
 
Title Tunable continuous wave emission via phase-matched second harmonic generation in a ZnSe microcylindrical resonator 
Description Data set for paper entitled: Tunable continuous wave emission via phase-matched second harmonic generation in a ZnSe microcylindrical resonator 
Type Of Material Database/Collection of data 
Year Produced 2015 
Provided To Others? Yes  
Impact First observation of phase-matched second harmonic generation in a ZnSe resonator via access to different modes. Data set contains results of mode analysis and experimental data. 
URL http://eprints.soton.ac.uk/376815
 
Description Drawn silicon fibre collaboration 
Organisation Clemson University
Country United States 
Sector Academic/University 
PI Contribution My team has been characterizing the optical properties of fibres made through this partnership, and investigating possible device functionality.
Collaborator Contribution Clemson and NTNU have been collaborating to make silicon fibre samples for my group. The preforms are made in NTNU and then drawn into fibres at Clemson.
Impact We typically publish several journal and conference papers together in each year, making it a highly fruitful collaboration. The collaboration is multi-disciplinary as it draws on expertise in optical physics and materials science.
Start Year 2013
 
Description Drawn silicon fibre collaboration 
Organisation Norwegian University of Science and Technology (NTNU)
Country Norway 
Sector Academic/University 
PI Contribution My team has been characterizing the optical properties of fibres made through this partnership, and investigating possible device functionality.
Collaborator Contribution Clemson and NTNU have been collaborating to make silicon fibre samples for my group. The preforms are made in NTNU and then drawn into fibres at Clemson.
Impact We typically publish several journal and conference papers together in each year, making it a highly fruitful collaboration. The collaboration is multi-disciplinary as it draws on expertise in optical physics and materials science.
Start Year 2013
 
Description OSA Student Chapter visit - University of Bath 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Postgraduate students
Results and Impact Gave a talk to around 60 students (mainly PGR) and staff as part of an event to promote diversity in STEM. Talk covered both career and research aspects.
Year(s) Of Engagement Activity 2020
 
Description OSA travelling lecture - University of Kent 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Postgraduate students
Results and Impact Around 40 postgraduate students and early career researchers, from a broad range of backgrounds (physics, chemistry and engineering), attended a seminar that I gave hosted by the OSA student chapter at the University of Kent. There were a number of questions before and afterwards as well as a lab tour of their facilities.
Year(s) Of Engagement Activity 2018
 
Description Royal Society Industry Engagement Event: The future of photonics 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Industry/Business
Results and Impact A one-day international conference held by the Royal Society aimed to bring together experts from academia and industry working on photonics technologies.
Year(s) Of Engagement Activity 2019
URL https://royalsociety.org/science-events-and-lectures/2019/10/tof-photonics/
 
Description Royal Society Meeting - Frontiers in Science 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Other audiences
Results and Impact Around 30 early career researchers in both the natural and social sciences attended a 3 day meeting. All presentations were recorded and posted on the Royal Society's website.
Year(s) Of Engagement Activity 2016
 
Description SPIE Visiting Lecturer - University of Auckland 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Postgraduate students
Results and Impact I was a visiting lecturer for the SPIE student chapter at the University of Auckland. I gave a lecture the described my career progression and how this linked to my current research interests, which sparked questions and discussions afterwards.
Year(s) Of Engagement Activity 2017