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SUMMARY:(SP Wednesday Workshop) - Towards lower losses in THz Quantum Casc
 ade Lasers - Mr Adam Klimont\, University of Cambridge\, Semiconductor Phy
 sics Group
DTSTART:20141008T131500Z
DTEND:20141008T141500Z
UID:TALK52473@talks.cam.ac.uk
CONTACT:Teri Bartlett
DESCRIPTION:Terahertz Quantum Cascade Lasers (QCLs) are complex heterostru
 cture devices\, where lasing action occurs between electronic levels in th
 e conduction band only — in other words\, they are unipolar lasers. The 
 levels are carefully designed and carried out by growing hundreds of nanom
 etre-thick GaAs/AlGaAs wells/barriers in an MBE chamber. The wafers are su
 bsequently fabricated into 200μm ridges and embedded in an unusual "surfa
 ce plasmon" waveguide — this is necessary in order to confine radiation 
 in sub-wavelength dimensions\, at the expense of high free carrier loss. A
 fter 10 years of development\, QCLs remain one of the best THz sources: th
 ey are compact\, tunable and reliable.\n\nI will briefly describe the prin
 ciple of operation of QCLs\, their design and fabrication. Then I will mov
 e on to talk about loss mechanisms\, which are a limiting factor in the te
 mperature performance of the lasers. I will propose a way of reducing loss
 es by changing the waveguide geometry\; I will show preliminary simulation
  results and discuss fabrication challenges for the proposed design.\n
LOCATION:Mott Seminar Room\, Cavendish Laboratory\, Department of Physics
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