Novel Quantum Cascade Laser technology leads to new products, processes and market opportunities
Submitting InstitutionUniversity of Glasgow
Unit of AssessmentGeneral Engineering
Summary Impact TypeTechnological
Research Subject Area(s)
Physical Sciences: Atomic, Molecular, Nuclear, Particle and Plasma Physics, Optical Physics, Other Physical Sciences
Summary of the impact
The commercialisation of Quantum Cascade Lasers (QCL) and the associated
novel fabrication processes developed at the University of Glasgow has
provided Compound Semiconductor Technologies Global Ltd (CSTG) with a new
foundry product supplying quantum cascade lasers for gas sensing, safety
and security, and military applications. This resulted in 40% turnover
growth from 2010-2012 and the company is now recognised as a global leader
in QCLs and their fabrication. Based on University of Glasgow research,
the company has created a manufacturing toolbox for the production of a
wide variety of QCL chip designs. CSTG has also achieved a world first,
manufacturing QCLs for systems that detect explosives at a safe distance
and can counter heat-seeking missile attacks on aircraft.
Quantum cascade lasers (QCLs) were first demonstrated by Federico
Capasso's group at Bell Laboratories in the USA in 1994. QCLs are highly
compact semiconductor chips, only 1mm long, that emit light in the
mid-infrared region of the spectrum enabling many gases of economic and
environmental importance to be sensed, e.g. methane and carbon dioxide.
Professor Charles Ironside in the School of Engineering at the University
of Glasgow (Senior Lecturer 1992-94, Reader 1994-99, Professor of Quantum
Electronics 1999-present) initiated his research into QCLs to diversify
the portfolio of applications that could be addressed with this
As QCL devices have important military applications, it was not possible
to access US manufactured lasers due to US Government regulations (ITAR)
controlling the export of defence-related material and services. No group
outside the USA had the ability to manufacture QCLs and so it was
necessary to independently discover the experimental means for growing the
epitaxial structures and to develop the techniques and processes that
would enable their reliable manufacture. This was achieved in 1998 by a
consortium comprising epitaxial growth and fabrication at the University
of Glasgow, led by Ironside, and device characterisation at the University
of Sheffield, led by Prof John Cockburn (Department of Physics and
Astronomy). They were the first outside the USA to demonstrate QCLs .
The University of Glasgow team included Colin Stanley (Professor
1992-2010), Jane McGill (Research Fellow 1987-88, Lecturer 1988-2000) and
PhD student Corrie Farmer.
Key challenges tackled by the consortium were developing the critical
etch and lithography processes that define the laser structure. These were
overcome by the development of wet and dry etch techniques, including the
use of reactive ion etching and inductively coupled reactive ion etching
techniques and using hydrogen silsesquioxane for QCL waveguide
The research continued with funding from EPSRC for the project "Quantum
cascade emission devices for IR optical sensing" (2000-2002,
GR/M46983/01). In collaboration with the University of Sheffield,
Edinburgh Sensors and GEC Marconi, a successful demonstration of
spectroscopy using room temperature QCLs was achieved.
From 1999-2000 Ironside, Dr Farmer (Research Assistant, 2000-present) and
PhD student Michel Garcia (2001-2003) collaborated with Dr N Langford and
Prof D Duxbury in the Physics Department at the University of Strathclyde
to develop QCLs for gas spectroscopy. The EPSRC funded "Ultra Sensitive
Spectroscopy Using QCLs" (GR/M69043/01) led to the discovery of an
intra-pulse chirp effect that tuned the laser in a way that made it
suitable for detecting gases . Cascade Technologies Ltd was founded, as
a University of Strathclyde spin-out, to manufacture sensing systems based
on this technique.
The `QCSENSE' project was funded by the DTI in 2006, in collaboration
with Cockburn at the University of Sheffield, Wyn Meredith, Commercial
Director, Compound Semiconductor Technologies Global Ltd (CSTG), Erwan
Normand, Chief Scientific Officer, Cascade Technologies and Bill Hirst,
Shell Global Solutions. Ironside, Miles Padgett (Professor of Physics,
1999-present) and Research Assistant Dr Thomas Slight (2006-2012) worked
with the consortium to develop 3.35 micron QCLs, the shortest wavelength
QCL at the time, for trace sensing of hydrocarbons such as ethane and
methane using the mid-infrared absorption of light by these gases .
Deep etched surface grating technology, based on initial work on
conventional direct bandgap lasers by John Marsh in 1995 (Lecturer
1986-96, Professor 1996-present), was used to make single-mode lasers.
These QCLs were suitable for robust, reliable and compact systems that
could be mounted on a mobile platform. Figure 1 illustrates the lateral
grating on the side wall of a QCL that ensures the laser operates at a
precise single frequency, which is ideal for sensing ethane.
Between 2010 and 2012, CSTG and Ironside collaborated on a Knowledge
Transfer Partnership (KTP) project increasing the commercial focus of the
research, with Slight as the KTP Associate. The project produced a QCL
with a novel laser geometry, giving very high spectral quality for
spectroscopy and sensing applications , and industrialised the research
processes. The project also produced a number of research outputs that
have become part of the suite of processes and designs now offered by
CSTG. These included an entirely new method for ensuring single mode
operation of QCLs with significantly reduced fabrication costs  and
QCLs with an integrated polarization mode converter which has applications
in ellipsometry .
References to the research
 C.D. Farmer, P.T. Keightley, C.N. Ironside, C.R. Stanley, L.R. Wilson
and J.W. Cockburn, A quantum cascade laser fabricated using planar
native-oxide layers, Appl. Phys.Letts. 77(1), 25-27, 2000. doi: 10.1063/1.126865
 M. Garcia, E. Normand , C.R. Stanley, C.N. Ironside, C.D. Farmer G.
Duxbury and N. Langford, An AlGaAs/GaAs quantum cascade laser operating
with a thermoelectric cooler for spectroscopy of NH3, Optics
Communications 226 39-43 2003. doi:
 T.J. Slight, G. Tandoi, D. Revin, A. McKee, S. Zhang, W. Meredith,
J.W. Cockburn, C. N. Ironside, Lambda =3.35um Distributed Feedback Quantum
Cascade Lasers with High Aspect Ratio Lateral Grating, IEEE Photonics
Technology Letters, 23(7), 420-422, 2011. doi: 10.1109/LPT.2010.2103358
 R. Phelan, T.J. Slight, B. Kelly, J. O'Carroll, A. McKee, D. Revin,
S. Zhang, A.B. Krysa, K.L. Kennedy, J.W. Cockburn, C.N. Ironside, W.
Meredith, J. O'Gorman, Room-Temperature Operation of Discrete-Mode
InGaAs-AlAsSb Quantum-Cascade Laser With Emission at 3.3microns, IEEE
Photonics Technology Letters, 22(17), 1273-1275, 2010.
 D. Dhirhe, T.J. Slight, C.C. Nshii and C.N. Ironside, A tunable
single-mode double-ring quantum-cascade laser, (Invited paper),
Semicond. Sci. Technol. 27, 094007, 2012. doi: 10.1088/0268-1242/27/9/094007
 D. Dhirhe, T. J. Slight, B. M. Holmes, D. C. Hutchings, and C. N.
Ironside, Quantum cascade lasers with an integrated polarization mode
converter, Optics Express, 20(23), pp. 25711-25717, 2012. doi: 10.1364/OE.20.025711
* best indicators of research quality
Details of the impact
Professor Charles Ironside's research on Quantum Cascade Lasers (QCLs)
has created commercial impact through two SMEs — Compound Semiconductor
Technologies Global (CSTG) and Cascade Technologies — and the development
of new products and processes for gas sensing, safety and security and
CSTG supplies advanced semiconductor optoelectronic devices to a range of
markets including counterterrorism, homeland security, and oil and gas.
For example, devices that sense minute quantities of explosive gases are
used for the stand-off detection of explosive devices including IEDs, and
the detection of hydrogen peroxide is used in combination with infrared
counter measures to dazzle heat-seeking missiles. The company serves both
fabless and vertically integrated customers in the UK, US, Europe and
Japan. In excess of 70% of the company revenues are derived from
high-value product exports. CSTG is now recognised as a global leader in
QCL fabrication as a direct result of the collaboration with the
University of Glasgow and achieved an increase in turnover of ~40% from
2010 to 2012.
Building on his world-leading research, Ironside, together with CSTG,
secured a KTP project in 2009 which has had a remarkable impact on CSTG's
profitability. This has been achieved through the creation of a
manufacturing toolbox, a generic QCL process library that can be used to
produce a wide variety of chip designs, hence establishing the company's
reputation in new applications and markets. The company has achieved world
firsts, in manufacturing QCLs for systems that detect explosives at a safe
distance and for countering heat-seeking missile attacks on aircraft.
This project integrated Ironside's knowledge of the design and optical
characterisation of QCLs into CSTG business, allowing the company to
harness the commercial potential of QCLs as an emerging mid-infrared laser
technology. This resulted in CSTG adding a new high-value laser device and
manufacturing process to their product range. The project also yielded new
fabrication processes and novel laser chip designs, enabling CSTG to
address a market need for innovative semiconductor foundry processes for
the manufacture of compact, mid-infrared micro-chip laser sources. The
Commercial Director at CSTG has stated that at least 60% of the company's
increase in turnover (between 2010 and 2012) could be attributed to these
mid-infrared products. CSTG's ability to access markets and clients
through the introduction of a QCL foundry service has resulted in new
contracts, customers, and the recruitment by the company, via a KTP, of
Thomas Slight from Ironside's research group. The impact of this
collaboration in terms of business profitability and expansion was
recognised by the award of Best KTP in Scotland in 2012.
In addition to the impact through CSTG, Ironside's QCLs were used to tune
a new intra-pulse spectroscopy technique. This led to a series of
successful gas phase molecular fingerprinting experiments. Cascade
Technologies was established in 2003 to capitalise on this novel
technique. The intra-pulse technology is now used within the spectroscopic
systems developed, manufactured and marketed by Cascade Technologies.
Their QCL based gas emission monitoring systems and gas analysers are used
for industrial emissions monitoring, process optimisation, analytical
chemistry and trace level applications. The systems are installed on the
production lines of products where integrity is critical, e.g. in the
manufacture of aerosol cans and inhalers, guaranteeing their integrity by
scanning to sense for escaping gases.
Sources to corroborate the impact