Transcript poster_photonics_openday_2005

Photonics Group
AR Adams, J Allam, K Homewood, TJC Hosea, D Lancefield, BN Murdin (Group Leader), G Reed, S Sweeney
Advanced Technology Institute, School of Electronics and Physical Sciences, University of Surrey, Guildford, GU2 7XH
Significant achievements
Silicon Photonics
Light emission from silicon
Motivation
• Cheap and efficient silicon-based light
emitters are needed for integration with
CMOS, with applications to all-silicon optical
communications (Fibre to the Home etc).
• Silicon waveguides and high speed
modulators are needed for optical
interconnects in microelectronics.
• This technology has come of age with recent
new achievements.
Integrated Intensity (a.u.)
W
• Dislocation engineering in silicon (patented
ULSI-compatible technology), published in
NATURE
• Semiconducting silicides (iron disilicide).
First serious silicon based LED, published in
NATURE (patented technology).
• Amorphous iron disilicide (a new
semiconductor discovered by us):
applications expected to be for a new
sustainable solar cell technology.
Silicon optical waveguides
• Dual grating-assisted directional coupling
between fibres and thin semiconductor
waveguides
Air
D
H
h=rH
Si
• Intel sponsorship of 2 students
SiO
2
• New grating assisted optical couplers (UK
patent).
Cross section of SOI waveguide and its mode
profile for quasi-TE and -TM polarisations
80 K
• New process for “Arrayed Waveguide
Grating” optical multiplexers (UK patent)
• Silicon-on-insulator (SOI) photonics including
MHz and GHz frequency Optical Phase
Modulators and optical racetrack resonators
• Research towards the first silicon injection
laser diode.
• Spin-out: Si-light Technologies Ltd, a startup company set up to exploit our silicon light
emission technologies.
45
40
Significant achievements
Si
35
S
30
EC
Total
25
S-related
level
20
15
τSi
τS
τNR
10
5
EV
0
0
50
100
150
200
Applied Current (mA)
Defect engineering of sulphur in silicon for
light emission at long wavelength
A silicon Bragg grating
interrogation system using
MEMS and optical circuits
(picture in collaboration with
BAE Systems)
SEM image showing the side view of 1st
order Bragg grating with grating period of
227nm and grating etch depth of 130nm
Significant Achievements
III-V Semiconductor Light Emitters
Motivation
Projects
• High (THz) bandwidth light sources are
needed for IT
• Gallium nitride light emitters for displays
and lighting (3 patents applied for)
• New wavelengths from UV to THz (far-IR)
are needed for a host of new sensing
applications
• Mid-infrared gas sensing lasers containing
antimony and nitrogen
• High efficiency emitters are needed for
energy saving and long-life displays and
lighting
The University of Surrey was awarded the
Queen's Anniversary Prize in 2002 for the work
of Professors Adams (pictured left) and Sealy
of the ATI. Collaborating with industry we have
made break-throughs in the development of
devices which have now become ubiquitous,
such as the strained-layer quantum well laser.
• Higher-speed, higher-power lasers for
information technology
• Vertical emission lasers for optical fibre
communications
Facilities
Professor Adams in the high pressure facility
• High Pressure is a very useful tool for
physics and materials science: in
semiconductors it affects nearly all important
properties including the energy of the
emitted light. It gives an insight into the inner
workings of the semiconductor laser.
Our systems can apply up to half a million
atmospheres and determine the impact on
electrical and optical properties of the device
• Specialist spectroscopy for nondestructive optoelectronic wafer testing
(from UV to IR) as an industrial tool
current
normalised
Normalisedthreshold
threshold current
2.0
1.8
1.5m
1.5m
I /I =0.80
Aug th
1.6
1.3m
1.3m
I /I =0.55
1.4
Aug th
1.2
1.0
Light emitters made from gallium nitride, and
related alloys give all the colours of the rainbow
and white besides (with CRHEA, France).
0.8
0.6
0.4
Radiative Current
Heat
Light
2
(~Eg )
0.2
New directions
0.0
0.80
0.85
0.90
0.95
1.00
1.05
1.10
Lasing Energy (eV)
lasing
energy
• Bio-molecule sensors
High pressure tunes the wavelength of
laser emitters and shows that infrared
lasers produce more heat than light
Our reflectance and photoluminescence
laboratory showing the different laser sources
that can be used for probing the samples
• New dilute-nitride avalanching
photodetectors with ultra-high sensitivity
(patent applied for)
Femtosecond dynamics
Motivation
Facilities
Significant Achievements
• Optical information systems will soon need to
operate with Terabit/s bandwidth, switching
light pulses on a sub-picosecond time-scale.
Advanced amplified femtosecond lasers
• Intense ultrashort (50 fs) pulses from UV to THz
‘FELIX’ free electron laser in Utrecht
• mid- to far-infrared picosecond pulsed source
complementing Surrey lasers
• First coherent spin manipulation in small
bandgap / high spin-orbit coupling materials
at room temperature (see fig below),
published in Physical Review
• Dynamics of charge transfer is a key issue in
hybrid and composite nanoscale materials
Projects
• Dynamics of semiconductor lasers
• THz dynamics of excitons
• Spin dynamics of narrow gap materials
Round-trip time
Bright pulse
frequency
• First measurements of picosecond relaxation
in silicon/germanium quantum cascade
structures published in Physical Review
3
New directions
2
polarisation
• Dynamical systems (i.e. those that do useful
work) that involve electronic, vibrational and
optical properties of photonic materials are
controlled by processes occurring on timescales as short as femtoseconds
• Hybrid narrow gap / ferromagnet spintronic
devices
B = 0.1 T
T = 300 K
• Ultra-fast spectroscopy under pressure
1
• Nanotube Nonlinear Waveguides for Next
Generation Electrophotonics
0
Dark pulse
-1
0
Relaxation period
Time (picoseconds)
Simulation of ultrashort pulse
propagation in semiconductor lasers
Femtosecond pulses circulating in a semiconductor
laser cavity reveal the inner workings of optical gain
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60
80
100
Time, ps
Electron spins in InAs semiconductor are
all aligned upwards by a femtosecond
pulse. The spins then precess around a
magnetic field, while relaxing.
• New photonic crystals with switchable
optical transmission, including novel inverse
opals from German Polymer Institute
• Precise material modification (direct writing)
using high intensity femtosecond pulses
• Optical sensors and solar cells using organic
/ semiconductor hybrids and composites
(collaboration with Nano-Electronics Centre)