High Power, High Frequency Mode-locked Semiconductor Lasers

Lead Research Organisation: University of Glasgow
Department Name: School of Engineering

Abstract

Semiconductor lasers are compact, low-cost sources of short pulses of light - and this is used in many applications, e.g. CD players (CD lasers operate at frequencies of a few MHz) and optical communications. For applications in optical communications ultra-short pulses are required at very high repetition frequencies, i.e. tens of GigaHertz (tens of billions of cycles per second) / and in the future even higher repetition rates are likely to be required. It is possible to switch semiconductor lasers on-and-off, directly, at frequencies up to about 40 GHz by using a pulsed current source but not much higher. Future optical communications systems are likely to need higher repetition frequencies - and these frequencies can be reached by using a method called mode-locking, where a special absorbing section within the laser cavity helps to form pulses, with the time between adjacent pulses being controlled by the round trip time for the cavity. But such pulses from mode-locked lasers have relatively low average power levels and are relatively long (typically a few picoseconds). For optical communications applications, lasers with shorter pulses and higher output power levels need to be developed.Another potential use of mode-locked lasers is in the generation of terahertz radiation. The Terahertz part of the electromagnetic frequency spectrum lies between the spectra for visible light and for microwaves. This non-ionising radiation is able to penetrate through materials that are opaque to light, such as paper, plastic, cloth and skin / so it can be used in security and medical applications. It can detect explosives and tumours - it is safer than x-rays because it does not ionise the material through which it passes and is better at differentiating between different types of soft tissue. Terahertz waves are typically generated by conversion from pulsed light sources that presently are both large and expensive to buy and to run. One of the aims of this project is to develop semiconductor lasers that produce pulses at very high frequencies (300 to 2000 Gigahertz) with enough output power to be used to generate Terahertz and sub-Terahertz waves with much increased efficiency. Lasers are needed that emit shorter pulses at higher repetition frequencies and with higher power output levels. This need can be met by using structures already designed to emit high powers and then adapting them for pulsed operation. We shall bring together high-power semiconductor lasers with mode-locked operation to develop lasers that emit short higher-power pulses at world-record repetition frequencies. We shall also investigate structures that can be integrated with the laser that can compress the light pulses even further - and also investigate exactly how the light interacts with the semiconductor material, thereby finding optimum designs of the laser structures for specific applications.

Publications

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Dylewicz R (2010) Fabrication of submicron-sized features in InP/InGaAsP/AlGaInAs quantum well heterostructures by optimized inductively coupled plasma etching with Cl2/Ar/N2 chemistry in Journal of Vacuum Science & Technology B, Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phenomena

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Hou L (2013) EML Based on Side-Wall Grating and Identical Epitaxial Layer Scheme in IEEE Photonics Technology Letters

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Hou L (2018) 1.55-µm AlGaInAs/InP Sampled Grating Laser Diodes for Mode Locking at Terahertz Frequencies in IEEE Journal of Selected Topics in Quantum Electronics

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Hou L (2012) AlGaInAs/InP Monolithically Integrated DFB Laser Array in IEEE Journal of Quantum Electronics

 
Description Subsequent to the completion of EP/E065112/1, related funding was won for a commercialisation project with local laser manufacturer CSTG. The aim of the project was to develop capability in the design, development, testing and manufacture of high speed and single frequency lasers for the optical access market. The project optimised existing and added new processes and designs leading to the introduction of a new high speed and single frequency laser product range. This work was possible due to the capability which was developed on EPSRC project EP/E065112/1 'High Power, High Frequency Mode-locked Semiconductor Lasers' in laser design, simulation and high speed characterisation. The devices developed on this subsequent project were related to those investigated on the original grant, and the skills and capability transferred.
The impact to CSTG has been significant. There has been 1 job created to date (KTP Associate), 10+ jobs safe-guarded, £3.5M attributed turnover, £10M+ in orders to date and £18M in additional anticipated revenue in 2017. There have been 3 new products introduced - 10G F-P laser, Mode expanded laser and a range of DFB lasers.
This project has allowed a new market for CSTG to be opened in Asia. Productivity has also increased because 10G products can command 3-5x higher prices than 2.5G products, yet chip manufacturing footprint is the same. The shift to 10G products will result in a corresponding higher profit margin per wafer for same manufacturing yield.
Exploitation Route Subsequent to the completion of EP/E065112/1, related funding was won for a commercialisation project with local laser manufacturer CSTG. The aim of the project was to develop capability in the design, development, testing and manufacture of high speed and single frequency lasers for the optical access market. The project optimised existing and added new processes and designs leading to the introduction of a new high speed and single frequency laser product range. This work was possible due to the capability which was developed on EPSRC project EP/E065112/1 'High Power, High Frequency Mode-locked Semiconductor Lasers' in laser design, simulation and high speed characterisation. The devices developed on this subsequent project were related to those investigated on the original grant, and the skills and capability transferred.
The impact to CSTG has been significant. There has been 1 job created to date (KTP Associate), 10+ jobs safe-guarded, £3.5M attributed turnover, £10M+ in orders to date and £18M in additional anticipated revenue in 2017. There have been 3 new products introduced - 10G F-P laser, Mode expanded laser and a range of DFB lasers.
This project has allowed a new market for CSTG to be opened in Asia. Productivity has also increased because 10G products can command 3-5x higher prices than 2.5G products, yet chip manufacturing footprint is the same. The shift to 10G products will result in a corresponding higher profit margin per wafer for same manufacturing yield.
Sectors Digital/Communication/Information Technologies (including Software)

URL http://userweb.eng.gla.ac.uk/charles.ironside/
 
Description Subsequent to the completion of EP/E065112/1, related funding was won for a commercialisation project with local laser manufacturer CSTG. The aim of the project was to develop capability in the design, development, testing and manufacture of high speed and single frequency lasers for the optical access market. The project optimised existing and added new processes and designs leading to the introduction of a new high speed and single frequency laser product range. This work was possible due to the capability which was developed on EPSRC project EP/E065112/1 'High Power, High Frequency Mode-locked Semiconductor Lasers' in laser design, simulation and high speed characterisation. The devices developed on this subsequent project were related to those investigated on the original grant, and the skills and capability transferred. The impact to CSTG has been significant. There has been 1 job created to date (KTP Associate), 10+ jobs safe-guarded, £3.5M attributed turnover, £10M+ in orders to date and £18M in additional anticipated revenue in 2017. There have been 3 new products introduced - 10G F-P laser, Mode expanded laser and a range of DFB lasers. This project has allowed a new market for CSTG to be opened in Asia. Productivity has also increased because 10G products can command 3-5x higher prices than 2.5G products, yet chip manufacturing footprint is the same. The shift to 10G products will result in a corresponding higher profit margin per wafer for same manufacturing yield.
First Year Of Impact 2015
Sector Digital/Communication/Information Technologies (including Software)
Impact Types Economic

 
Description Knowledge Transfer Partnership
Amount £57,837 (GBP)
Funding ID KTP8847 
Organisation Innovate UK 
Sector Public
Country United Kingdom
Start 07/2012 
End 08/2014