Photonics Group

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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
Silicon Photonics

• Significant achievements
• Light emission from silicon
• 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.
• Research towards the first silicon injection
  laser diode.
• Spin-out Si-light Technologies Ltd, a start-up
  company set up to exploit our silicon light
  emission technologies.

• Significant achievements
• Silicon optical waveguides
• Dual grating-assisted directional coupling
  between fibres and thin semiconductor waveguides
• Intel sponsorship of 2 students
• New grating assisted optical couplers (UK
  patent).
• 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

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• 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.

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Cross section of SOI waveguide and its mode
profile for quasi-TE and -TM polarisations
SEM image showing the side view of 1st order
Bragg grating with grating period of 227nm and
grating etch depth of 130nm
Defect engineering of sulphur in silicon for
light emission at long wavelength
III-V Semiconductor Light Emitters
Significant Achievements 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. 

• Projects
• Gallium nitride light emitters for displays and
  lighting (3 patents applied for)
• Mid-infrared gas sensing lasers containing
  antimony and nitrogen
• Higher-speed, higher-power lasers for information
  technology
• Vertical emission lasers for optical fibre
  communications

• Motivation
• High (THz) bandwidth light sources are needed for
  IT
• New wavelengths from UV to THz (far-IR) are
  needed for a host of new sensing applications
• High efficiency emitters are needed for energy
  saving and long-life displays and lighting

Professor Adams in the high pressure facility

• Facilities
• 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 non-destructive
  optoelectronic wafer testing (from UV to IR) as
  an industrial tool

Light emitters made from gallium nitride, and
related alloys give all the colours of the
rainbow and white besides (with CRHEA, France).

• New directions
• Bio-molecule sensors
• New dilute-nitride avalanching photodetectors
  with ultra-high sensitivity (patent applied for)

Our reflectance and photoluminescence laboratory
showing the different laser sources that can be
used for probing the samples
High pressure tunes the wavelength of laser
emitters and shows that infrared lasers produce
more heat than light
Femtosecond dynamics

• Facilities
• 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
• Projects
• Dynamics of semiconductor lasers
• THz dynamics of excitons
• Spin dynamics of narrow gap materials

• Motivation
• Optical information systems will soon need to
  operate with Terabit/s bandwidth, switching light
  pulses on a sub-picosecond time-scale.
• 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 time-scales
  as short as femtoseconds
• Dynamics of charge transfer is a key issue in
  hybrid and composite nanoscale materials

• Significant Achievements
• First coherent spin manipulation in small bandgap
  / high spin-orbit coupling materials at room
  temperature (see fig below), published in
  Physical Review
• First measurements of picosecond relaxation in
  silicon/germanium quantum cascade structures
  published in Physical Review

• New directions
• Hybrid narrow gap / ferromagnet spintronic
  devices
• Ultra-fast spectroscopy under pressure
• Nanotube Nonlinear Waveguides for Next Generation
  Electrophotonics
• 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)

Round-trip time
Bright pulse
Dark pulse
Relaxation period
Electron spins in InAs semiconductor are all
aligned upwards by a femtosecond pulse. The spins
then precess around a magnetic field, while
relaxing.
Simulation of ultrashort pulse propagation in
semiconductor lasers
Femtosecond pulses circulating in a semiconductor
laser cavity reveal the inner workings of optical
gain