Modular Ultrafast Sources

Lead Research Organisation: University of Cambridge
Department Name: Engineering

Abstract

Since the development of the first Kerr-lens mode-locked lasers in 1990, practical femtosecond lasers in a wide variety of configurations have delivered handsomely to a significant number of major scientific developments. It has to be recognised that the application space remains limited by the cost, complexity, skilled-user requirements and restricted flexibility of the current generation of ultrafast lasers. In this proposed joint project we seek to lead the way in the development of a new generation of ultrafast lasers. By adopting a modular approach for laser design we am aiming to demonstrate a platform from which lasers can be designed to address a wide range of user-specific requirements. By taking this approach, lasers for use in communications, for example, will have the necessary high repetition rates and low peak powers whereas for biophotonics high peak powers will be delivered to take full advantage of exploitable optical nonlinearities. We plan to work with vibronic crystals in both bulk and waveguide geometries and semiconductor quantum dot structures as the primary gain media. Although vibronic crystals have been deployed widely in ultrashort-pulse lasers the flexibility offered by conventional laser designs is very limited. To remedy this situation we intend to revolutionise cavity design to enable electrical control of the laser output parameters. For example, we wish to provide a means to users to change from an unmodelocked status to a femtosecond-pulse regime at the flick of switch. Also, by exploiting waveguiding in the vibronic crystals we are confident that we can introduce a new generation of highly compact lasers that will combine many of the advantages of a semiconductor laser with the most attractive features of crystal based devices. In some preliminary work in the Ultrafast Photonics Collaboration we have shown the potential of semiconductor quantum dot structures as broadband gain media that Can support the amplification and generation of femtosecond optical pulses. We now seek to build on those promising results and make the push towards truly flexible ultrafast lasers that will be amenable to external electronic control of the gain and loss components. Progress is expected to lead to a new generation of lasers that can give applications compatibility that far exceeds that available in traditional laser system designs. Within this strategy we plan to employ hybrid approaches where the benefits of semiconductor lasers will be combined with the energy storage capabilities of crystals to deliver compact and rugged sources having pulse characteristics that cover a range of durations, energies and profiles.A major part of this project effort will be devoted to the development of control functionality in ultrafast lasers. The intention is to use direct electrical control of intracavity components to deliver designer options for pulse shaping, modulated data streams, wavelength tuning and tailored dispersion. To ensure that this research is applicable we will evaluate the laser developments in the context of a set of identified demonstrators. These implementations will be used to show how design flexibility can deliver optimised lasers for biological, medical, communications and related applications.We have put together a research team having complementary of expertise and established track records of international excellence in photonics. This project as a whole will be managed from St Andrews University but all three research groups will undertake interactive research on all aspects of the laser development. We are confident that the work of this team will represent cutting-edge fundamental and translational research and it should represent a world leading strength for the UK in the development of new ultrafast lasers.
 
Description Since the development of the first Kerr-lens mode-locked lasers in 1990, practical femtosecond lasers in a wide variety of configurations have delivered handsomely to a significant number of major scientific developments. It has to be recognised however that the application space still remains limited by the cost, complexity, skilled-user requirements and restricted flexibility of the current generation of ultrafast lasers. In this joint project involving St Andrews, Strathclyde and Cambridge Universities, we have sought to lead the way in the development of a new generation of ultrafast lasers. By adopting a modular approach in laser design we have demonstrated a platform from which lasers can be designed to address a wide range of user-specific requirements. By taking this approach, lasers for use in communications, for example, have been developed with the necessary high repetition rates and low peak powers whereas for biophotonics systems have been developed with higher peak powers but at lower rates to take full advantage of exploitable optical nonlinearities. Within the project modular systems were developed using both vibronic gain crystals in both bulk and waveguide geometries and semiconductor diode laser structures as the primary gain media.

Research at Cambridge primarily focussed on diode laser systems, though collaborating with the other groups. Building on the work in the Ultrafast Photonics Collaboration we demonstrated that quantum dot laser diodes could operate with outstanding performance as mode-locked sources. New device structures were developed to enable not only the generation but also the modulation and amplification of the pulses for the first time, using the modular approach original proposed. Using this new generation of lasers, work with St Andrews University led to the first remote control of the laser from distance over the web, as demonstrated for a Cambridge laser remotely controlled in St Andrews and demonstrated during a workshop there. This met the goal of the project to demonstrate control functionality in ultrafast lasers for the first time, the demonstrations taking account of known biological, medical, communications and related applications.

At Cambridge we were also delighted that we were able to extend the project to (i) introduce studies in ML lasers using carbon nanotube saturable absorbers, which have been taken up by St Andrews, and (ii) a new form of pulse generation in quantum well and quantum dot laser diodes which would allow much greater potential pulse performance under flexible generation conditions in the future. Here we were able to demonstrate superradiance for the first time, showing the generation of femtosecond optical pulses on demand at repetition rates of up to some 100s of MHz. These pulses are particularly well suited for a number of biomedical applications. First demonstrations were achieved for QW, QD and InGaN devices. A major issue with this work has been whether the pulses are essentially only noise bursts, and hence targeted work focussed on this, this resulting in the important first demonstration of ultrahigh coherence in superradiance, in contrast to the properties of any noise burst.

We have been very grateful to EPSRC for opportunity to work within a research team having complementary of expertise and established track records of international excellence in photonics. We are delighted that the work of the team has led to cutting-edge fundamental and translational research and it should represent a world leading strength for the UK in the development of new ultrafast lasers.
Exploitation Route We continue to research on various aspects of short pulse generation in diode lasers, and have been engaged in several EU and UK projects in advancing the field. Of particular interest is the the development of a single chip femtosecond laser source, which we now believe is feasible using superradiance. We have been in discussions with the Universities of Cardiff and Glasgow in the past two years, and an unsuccessful application was submitted to extend this work. We do believe that applications of short pulses could be used in sensing, healthcare, analysis and communications. Very recently indeed we have been awarded an industrial grant from a Chinese company to develop a variant of a laser-based system for high performance oscillator applications.
Sectors Digital/Communication/Information Technologies (including Software)

Electronics

Environment

Healthcare

Manufacturing

including Industrial Biotechology

Pharmaceuticals and Medical Biotechnology

URL http://www.st-andrews.ac.uk/physics/music/research.html
 
Description In addition to publications, this grant led to several new research avenues, these in turn attracting UK and European funding. In particular the work on short pulse generation in blue laser diodes proved to be most successful, with several companies interested in exploring potential applications. Very recently we have attracted industrial funding to extend laser concepts for oscillator applications.
First Year Of Impact 2010
Sector Digital/Communication/Information Technologies (including Software),Electronics,Healthcare
Impact Types Economic

 
Description European Union EU Brussels
Amount £216,000 (GBP)
Funding ID FP7 ICT 
Organisation European Commission 
Sector Public
Country European Union (EU)
Start 03/2009 
End 07/2012
 
Description Huawei CAPE mode OFDM-ECDMA Access Network
Amount £69,821 (GBP)
Organisation Huawei Technologies 
Sector Private
Country China
Start 03/2014 
End 03/2015
 
Title Superradiance Model 
Description A novel theoretical model for a relatively new form of ultrashort high power generation mechanism in semiconductor lasers-superradiance (SR), which has the potential to match the performance of large main frame lasers. 
Type Of Material Computer model/algorithm 
Provided To Others? No  
Impact The first spatially-resolved, travelling-wave field model of SR pulse generation in a semiconductor medium is reported which includes polarization dynamics, a spatially resolved saturable absorber and a spectrally resolved gain profile. The interplay of the ultrafast processes enabling SR in semiconductor laser devices is understood, having sought to compare experimental and theoretical results directly and investigate methods of device optimization. To determine optimum SR emission performance, the influence of driving conditions, the role of device geometry and optical bandwidth are compared and contrasted as a route to enhance high power femtosecond pulses. While pulse duration can be significantly reduced through careful absorber length to cavity length ratio specification, stability is compromised in this case. However an increased spectral gain bandwidth of up to 150 nm is predicted to allow reductions of pulse durations down to 10 fs pulses with over 500 W peak powers without further degradation in pulse stability. This model thus shows that broad-gain media such as chirped quantum well devices or quantum dot devices should be potential candidates for SR. 
 
Description Collaboration between Cambridge and TU/e in short pulse generation 
Organisation Eindhoven University of Technology
Country Netherlands 
Sector Academic/University 
PI Contribution I built the first theoretical model to validate the Dicke superradiance experiments in semiconductor lasers.
Collaborator Contribution Prof. K.A.Williams helped and discussed with me in building the Dicke superradiance model.
Impact We have published several papers on this collaboration in Superradiance. [1]"Theoretical model for Dicke superradiance in a semiconductor laser device", X Guo, K A Williams, V Olle, A Wonfor, R V Penty and I H White, IEEE Photonic Technology Letters, Vol 23, Issue 23, pp 1817-1819, 2011 [2]"Numerical simulation of Dicke superradiance in a semiconductor laser device", X Guo, K A Williams, V F Olle, A Wonfor, R V Penty and I H White, Integrated Photonics Research Conference, Silicon and Nanophotonics, Toronto, 2011 [3]"Theoretical model for Dicke superradiance in a semiconductor laser", X Guo, K A Williams, V F Olle, A Wonfor, R V Penty and I H White, Semiconductor and Integrated Opto-Electronics Conference, Cardiff, 2011
Start Year 2009