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Publications
VECSEL papers and reading.

Links
Useful VECSEL, Laser and Semiconductor information.
 
Access my PhD Thesis
"Mode-Locked Vertical-External-Cavity Surface Emitting Lasers"

 

 

 

  
My research is in the area of Optically Pumped Semiconductor Vertical-External Cavity Surface-Emitting Lasers (OP-VECSELs). I studied towards my PhD in mode-locked VECSELs at the University of Southampton in the School of Physics and Astronomy (2002-2006). The work of my PhD focussed on achieving short, sub-picosecond pulses from VECSELs in the Infrared. I fibre-amplified VECSEL pulses to achieve high powers, and worked extensively on the design and fabrication of a compact, >100GHz ML-VECSEL for optical clocking applications. My PhD thesis is entitled 'Mode-Locked Vertical-External-Cavity Surface Emitting Lasers' - you can access it via this link.
I currently work at the Institute of Photonics at the University of Strathclyde as a Research Fellow, investigating visible VECSELs. My particular focus is on optimisations of the nonlinear frequency conversion of Red VECSELs into the UV (pictured right), investigating new nonlinear materials, and tuning methods to improve the performance of these devices.

 
What is a VECSEL?

  • VECSELs are Vertical-External Cavity Surface-Emitting Lasers.
    To learn more about lasers, click here to see my simple tutorial, visit howstuffworks.com, or explore some of the links from my research links page.
  • The VECSEL's unique external cavity design sets it aside from other all-semiconductor lasers. The external cavity enforces a low-divergence, circular, near-diffraction-limited, high quality output beam.
  • The semiconductor gain sample active region is composed of GaAs with InGaAs strain-compensated quantum wells. The emission wavelength of this structure can be tailored by design. The quantum wells have a wide gain bandwidth which is ideal for ultra-short pulse generation, and spectroscopic applications.
  • In the gain sample, a Bragg reflector is grown behind the active region. This carefully designed structure gives more than 99.9% reflectivity.
  • Optical pumping of the gain sample allows high power operation avoiding the problems of carrier filamentation and post-growth processing associated with electrical pumping. Efficient pump absorption in the active region means that only a single/double pump pass of pump light through the active region is required.
  • The VECSEL acts much like a thin disk solid state laser, and shows potential for power scalability due to its excellent thermal properties.
  • Access to external cavity allows manipulation of the laser output. Frequency doubling, mode-locking and spectroscopy are amongst these manipulative applications.
  • At the Institute of Photonics, we frequency double red VECSELs into the UV by inserting a nonlinear crystal into the external cavity of the laser.
  • At Southampton, I was involved in the passive mode-locking of VECSELs using an external cavity semiconductor saturable absorber mirror (SESAM) to give a train of short pulses in the laser output.

     

     

    Learn more:

    Click here for a list of papers in the VECSEL field.

    Click here for a list links related to VECSELs and semiconductor physics.


 

Any views expressed on these pages are not necessarily those of other bodies mentioned.
e-mail me: foreman.hannah@yahoo.com
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