Laser-Engineered Silicon: Manufacturing Low Cost Photonic Systems

Lead Research Organisation: University of Southampton
Department Name: Optoelectronics Research Centre (ORC)

Abstract

Silicon photonics promises to revolutionize modern optoelectronics by allowing for dense integration of components that feature the best optical and electronic functions of the material. In recent years great progress has been made in this area, with many silicon photonic devices now meeting (or exceeding) the performance requirements of state-of-the-art systems. This includes ultra-low loss interconnects as well as high speed optical regenerators, amplifiers, modulators, and detectors, which form the building blocks for photonic circuits. However, to date, much of this progress has been achieved on silicon-on-insulator (SOI) platforms with a thick buried oxide layer, which are largely incompatible with electronic device development, and relatively expensive, thus precluding truly integrated systems from reaching the high-volume market. Consequently, there are still crucial challenges to overcome before the performance benefits of SOI photonics outweigh the costs and design constraints, leaving the door open for alternative platforms to be considered.

In this programme we propose to develop a low cost and low temperature laser materials processing procedure to fabricate high quality polycrystalline semiconductor photonic platforms that will rival the performance of their SOI counterparts. Laser processed polycrystalline materials are already well-established for use in electronic technologies where some performance can be sacrificed in favour of reduced processing costs, for example, in the backplanes of smart phones and televisions. However, if the polycrystalline grains can be grown as large as the individual components, then the optical (and electronic) properties will approach those of the single crystal materials. By building on the platform established by the electronics community, this work seeks to grow large grain polycrystalline materials to realize low loss photonic components. Importantly, the high localization of this laser crystallization procedure directly alleviates issues associated with multi-material and multi-layer photonic device integration, and can also be used to modify or repair the individual components at a late stage in the fabrication, helping to increase the production yield and reduce the costs of integrated systems. Furthermore, this method offers the unique advantage of removing the substrate dependence from semiconductor photonics, thus offering the possibility to extend the application space through the use of substrate materials with enhanced optical functionality, increased transparencies, or even flexible plastics. By reducing costs and barriers associated with device fabrication, our innovative project will set the scene for wide spread use of laser-engineered semiconductor photonic components in mainstream optoelectronic systems.

Planned Impact

This proposal promises to transform the next generation of optoelectronic systems by reducing the barriers and costs associated with silicon photonic device fabrication and integration. This research is perfectly aligned with the EPSRC theme "Photonics for Future Systems", and we believe could ultimately have significant economic and societal impact in the areas of ICT, sensing, and manufacturing. In terms of market size, photonics21 (European Public-Private-Partnership) estimates the global market for optical components will be worth 30B euros in 2015, with the EU share approaching 50%.

ICT: The integrated polysilicon photonics platforms developed through our proposed work have the potential to increase the speed and capacity of data transport systems, whilst at the same time lowering the manufacturing costs, reducing energy requirements, and increasing production yields. Importantly, low cost polysilicon photonic components such as interconnects, modulators, and photodetectors, have already been identified by the leading semiconductor company Intel as a key step towards truly realizing the high density integration of optical and electronic devices. We expect that as the technology matures other major computer (IBM) and communication companies (Finisar) will find similar merit.

Sensing: As the laser-engineering process removes many substrate restrictions, there are several material platforms that could be established for use in biological or chemical sensing. For example, cheap, flexible, and disposable sensors developed on plastic substrates could find use as wearable monitoring systems, supporting growth in several markets such as point of care diagnostics and wearable electronics. Alternatively, more robust systems built on germanium-on-sapphire platforms, that offer the potential to operate over the important molecular 'finger-print' spectral region, could be used for rapid (in-field) identification of different types of hazardous chemicals/materials. Thus, the impact of this work could also feed into the EPSRC themes "Healthcare Technologies" and "Global Uncertainties".

Manufacturing: The UK has a strong laser manufacturing industry (e.g., SPI Lasers, Elforlight, Oxford Lasers), and the importance of laser-based manufacturing has been recognised through the establishment of an EPSRC Centre for Innovative Manufacturing in Laser-Based Production Processes (http://www.cim-laser.ac.uk/). Currently one of the major industrial growth markets for Excimer lasers is in materials processing of low cost electronic semiconductor electronic chips, and we can expect that new markets will open up through the expansion of these processing procedures to photonic components and systems. Our partnership with Elforlight and SPI Lasers demonstrates the relevance of our proposal to this sector and their confidence in this technology, even at this early stage. Furthermore, the low energies and temperatures of our process procedures also align with EPSRCs requirements for green, sustainable manufacturing procedures.

The successful outcomes of our proposed work will ultimately help to shift the focus away from single crystal, single layer optoelectronic platforms to more flexible, 3D integrable polysilicon alternatives. As our programme is largely centred on materials optimization, much of the immediate impact is likely to be within the academic community. However, as there is already interest within the industrial community, we expect that the commercial value of this approach will soon be widely recognized. Thus, by training new staff in this emerging area we will ensure that the UK has a solid skill and knowledge base to quickly capitalize on future industrial developments.
 
Description This proposal seeks to establish laser-engineered silicon photonic components as low cost solutions for use in highly integrated optoelectronic systems. The components are first deposited in an amorphous form, using a low cost and low temperature process, before being processed with a laser to convert it into crystalline silicon. The procedure is highly localized and so can be used to individually tune the properties of different components within an integrated circuit. Most of our work to date has focused on optimizing the laser processing parameters to achieve high quality single-crystal like silicon waveguides with micro/nanoscale dimensions. So far we have managed to produce silicon waveguides that are composed of single-crystal grains with lengths on the order of a few millimetres, so that each waveguide consists of only a few grains. The corresponding transmission losses have been measured to be as low as ~5 dB/cm, which is lower than any previously reported values for silicon waveguides of this type. As a result, this has opened a route to the first demonstration of nonlinear propagation in this material system, which is an important step towards the development of components that can be used for high speed, all-optical signal processing. More recently we have extended this work to laser processing silicon-germanium alloys where, as well as being able to crystallise the starting amorphous material, we can also use the heat treatment to tune the material composition to write waveguides and functional components, such as gratings, directly in to the films. The findings from this research will ultimately pave the way to the realization of highly functional photonic circuits that could, in future, be directly integrated with electronic layers to realize a complete optoelectronic chip.
Exploitation Route We expect that this waveguide fabrication method will be adopted by other researchers working in this area, and could even be employed in silicon photonics industries when the process is optimized.
Sectors Digital/Communication/Information Technologies (including Software),Electronics,Manufacturing, including Industrial Biotechology

 
Description EPSRC Research Fellowship
Amount £1,150,136 (GBP)
Funding ID EP/P000940/1 
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Academic/University
Country United Kingdom
Start 02/2017 
End 02/2022
 
Description Electronic-Photonic Convergence: A Platform Grant
Amount £1,477,730 (GBP)
Funding ID EP/N013247/1 
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Academic/University
Country United Kingdom
Start 04/2016 
End 03/2021
 
Description Collaboration on low cost integrated photonic platforms 
Organisation University of Toronto
Country Canada 
Sector Academic/University 
PI Contribution N/A
Collaborator Contribution Prof J. S. Aitchison is providing guidance to our work on the development of novel material integrated platforms.
Impact We have obtained one funded grant with University of Toronto as our partners.
Start Year 2015
 
Description Collaboration regarding modelling of laser-materials interactions 
Organisation HiLASE Centre of the Institute of Physics AS CR
Country Czech Republic 
Sector Academic/University 
PI Contribution We have produced a number of samples fabricated via laser crystallization for them to model and compare with our experimental results.
Collaborator Contribution They have modelled our experimental findings, helping us to understand the light-matter interactions in our material.
Impact We have produced one nature materials paper from this collaboration to date, and have had two grant proposals funded, on which they are a partner institute. This collaboration is multi-disciplinary as it combines experimental laser physics with computational physics.
Start Year 2015
 
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