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Author Walther, Christoph; Scalari, Giacomo; Faist, Jerome; Beere, Harvey; Ritchie, David openurl 
  Title Low frequency terahertz quantum cascade laser operating from 1.6 to 1.8 THz Type Journal Article
  Year 2006 Publication Applied Physics Letters Abbreviated Journal Appl. Phys. Lett.  
  Volume 89 Issue (up) Pages 231121(1-3)  
  Keywords QCL, 360 uW at 1.6 THz  
  Abstract The authors report a GaAs/Al0.1Ga0.9As quantum cascade laser based on a bound-to-continuum transition optimized for low frequency operation. High tunability of the gain curve is achieved by the Stark effect and laser emission is measured between 1.6 and 1.8 THz. Pulsed mode operation up to 95 K and continuous wave operation up to 80 K are reported. The dynamical range in current is as high as 43%.  
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  Notes Approved no  
  Call Number Serial 629  
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Author Sekine, Norihiko; Hosako, Iwao openurl 
  Title Intensity modulation of terahertz quantum cascade lasers under external light injection Type Journal Article
  Year 2009 Publication Applied Physics Letters Abbreviated Journal Appl. Phys. Lett.  
  Volume 95 Issue (up) Pages 201106(1-3)  
  Keywords QCL modulation, THz, terahertz  
  Abstract We investigated the light-current characteristics of terahertz (THz) quantum cascade lasers under external light injection, which excites interband transitions in the active materials. It was found that the amount of reduction in the THz power was constant for all injection currents above threshold, and the dependence of the reduction amount on the wavelength of the external light was observed to show a resonancelike feature. The dominant intensity modulation mechanism was found to be the loss change caused by interband transitions in the active region. Further, the effective coupling efficiency plays an important role in the intensity modulation.  
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  Notes Approved no  
  Call Number Serial 630  
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Author Kumar, Sushil; Chan, Chun Wang I.; Hu, Qing; Reno, John L. openurl 
  Title A 1.8-THz quantum cascade laser operating significantly above the temperature of hw/k Type Journal Article
  Year 2011 Publication Nature Physics Abbreviated Journal  
  Volume 7 Issue (up) Pages 166-171  
  Keywords QCL, 2 mW at 155 K and 1.8 THz  
  Abstract Several competing technologies continue to advance the field of terahertz science; of particular importance has been the development of a terahertz semiconductor quantum cascade laser (QCL), which is arguably the only solid-state terahertz source with average optical power levels of much greater than a milliwatt. Terahertz QCLs are required to be cryogenically cooled and improvement of their temperature performance is the single most important research goal in the field. Thus far, their maximum operating temperature has been empirically limited to ~planckω/kB, a largely inexplicable trend that has bred speculation that a room-temperature terahertz QCL may not be possible in materials used at present. Here, we argue that this behaviour is an indirect consequence of the resonant-tunnelling injection mechanism employed in all previously reported terahertz QCLs. We demonstrate a new scattering-assisted injection scheme to surpass this limit for a 1.8-THz QCL that operates up to ~1.9planckω/kB (163 K). Peak optical power in excess of 2 mW was detected from the laser at 155 K. This development should make QCL technology attractive for applications below 2 THz, and initiate new design strategies for realizing a room-temperature terahertz semiconductor laser.  
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  Notes Approved no  
  Call Number Serial 631  
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Author Williams, Benjamin S. openurl 
  Title Terahertz quantum-cascade lasers Type Journal Article
  Year 2007 Publication Nature Photonics Abbreviated Journal  
  Volume 1 Issue (up) Pages 517-525  
  Keywords QCL review  
  Abstract Six years after their birth, terahertz quantum-cascade lasers can now deliver milliwatts or more of continuous-wave coherent radiation throughout the terahertz range — the spectral regime between millimetre and infrared wavelengths, which has long resisted development. This paper reviews the state-of-the-art and future prospects for these lasers, including efforts to increase their operating temperatures, deliver higher output powers and emit longer wavelengths.  
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  Notes Approved no  
  Call Number Serial 632  
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Author Shah, Jagdeep; Pinczuk, A.; Gossard, A. C.; Wiegmann, W. openurl 
  Title Energy-loss rates for hot electrons and holes in GaAs quantum wells Type Journal Article
  Year 1985 Publication Phys. Rev. Lett. Abbreviated Journal Phys. Rev. Lett.  
  Volume 54 Issue (up) Pages 2045-2048  
  Keywords 2DEG, GaAs/AlGaAs, heat flow, electron-phonon, hole-phonon, carrier-phonon, interactions  
  Abstract We report the first direct determination of carrier-energy-loss rates in a semiconductor. These measurements provide fundamental insight into carrier-phonon interactions in semiconductors. Unexpectedly large differences are found in the energy-loss rates for electrons and holes in GaAs/AlGaAs quantum wells. This large difference results from an anomalously low electron-energy-loss rate, which we attribute to the presence of nonequilibrium optical phonons rather than the effects of reduced dimensionality or dynamic screening.  
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  Notes Approved no  
  Call Number Serial 633  
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