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Details of Grant 

EPSRC Reference: GR/H82471/01
Principal Investigator: De La Rue, Honorary Professor R
Other Investigators:
Marsh, Professor JH Stanley, Professor C Aitchison, Professor S
Arnold, Professor J Wilkinson, Professor C Laybourn, Professor PJR
Ironside, Professor CN
Researcher Co-Investigators:
Project Partners:
Department: Electronics and Electrical Engineering
Organisation: University of Glasgow
Scheme: Standard Research (Pre-FEC)
Starts: 01 October 1992 Ends: 01 August 1995 Value (£): 1,473,377
EPSRC Research Topic Classifications:
Optical Communications Optoelect. Devices & Circuits
EPSRC Industrial Sector Classifications:
Aerospace, Defence and Marine Communications
Related Grants:
Panel History:  
Summary on Grant Application Form
Rolling grant to develop photonic integrated circuit technology and devices for ultra-high speed optical fibre communication systems, in particular for a fully integrated all-optical clock recovery sub-system Fundamental studies and applications of quantum well intermixing processes Design fabrication and assessment of integrated lasers, in particular modelocked, Q-switched, and extended cavity lasers MBE growth of the GaInAs/AlGaInAs material system for optoelectronic devices Theoretical work on soliton-based optoelectronic systems, device modelling and process characteristicsProgress:Quantum Well Intermixing as an Integration Technology:Successful intermixing in the GaAs/AlGaAs system, particularly using fluorine impurity induced intermixing, has been demonstrated. TEM studies demonstrate that fluorine intermixed material is of very material quality. Impurity free vacancy disordering can produce even larger blue shifts (> 100 meV) and extended cavity lasers and extended cavity DBR lasers have been demonstrated using IFVD. Extended cavity (total length 2.5 mm) mode locked lasers have been recently fabricated. In 1.5 -m devices, fluorine IID induces bandgap increases of up to 40 meV on rapid thermal annealing and extended cavity lasers have been demonstrated using fluorine intermixing. In addition, a laser intermixing process, photo-absorption induced disordering (PAID) has been used to intermix InGaAs/InGaAsP quantum well laser structures under a separate grant. Devices and Systems:Two section CPM lasers fabricated which produce near transform limited pulses with repetition frequencies of 80 to 130 GHz (depending on cavity length). In addition, CPM lasers containing 3 saturable absorbers and 4 circulating pulses operate at 350 GHz. Two section Q-switched lasers fabricated with repetition frequencies as high as 16 GHz with pulse energies of 5 pJ. An novel waveguide autocorrelator is being developed. A 10/20 GHz digital test-bed is being set up. Molecular Beam Epitaxy:MBE growth of high optical quality AlGaAs-GaAs for various devices has continued. Oxide stripe lasers have Jth < 200 A cm-2 when grown at Ts+700-710oC. A valved As2 source is being developed in collaboration with the MBE system supplier. It has proved effective for quickly setting the best As2 flux for growing AlGaAs at high temperature, and GaInAs and AlInAs under optimum conditions, by examining RHEED surface reconstructions or oscillations. Analysis of GaInAs and AlInAs growth data shows close agreement between theory and experiment. Low threshold current 1.5 -m AlGaInAs/GaInAs quantum well lasers have been produced. Modelling:We have implemented a finite-difference BPM (FD-BPM) on parallel processing machines, and have identified the Chung-Dagli Explicit FD method as most suitable for parallel-processor implementation. This has been used to model, in 3D, a cascaded second-order nonlinear all-optical switch. The mode-locked semiconductor laser has been modelled as an element for all-optical clock extraction from a digital pulse stream. A time-domain model predicts locking to external periodic waveform by saturable absorber bleaching. The locking range of the laser is 0.1-0.2% of the mode-locked frequency, depending on the pulse energy of the control signal, and is 2-3 times larger for positive detuning than for negative detuning. We have predicted saturation of Gordon-Haus noise in strongly interacting soliton trains, with a consequent possible increase a factor of 2.5 in transatlantic capacity using pulse-position modulation and sub-band coding of solitons. In addition, a general mathematical stability model for long distance soliton propagation has been formulated.
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