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SUMMARY:Effect of optical feedback on Quantum Cascade Lasers - Dr Francesc
 o Mezzapesa\, Università degli Studi e Politecnico di Bari\, Italy
DTSTART:20150511T131500Z
DTEND:20150511T141500Z
UID:TALK58381@talks.cam.ac.uk
CONTACT:Teri Bartlett
DESCRIPTION:Delayed optical feedback can be easily generated in all class 
 of coherent light emitters when part of the output radiation is re-coupled
  into the laser cavity\, following interaction with any external objects (
 e.g.\, reflecting or diffusive targets). Semiconductor lasers have exhibit
 ed the largest sensitivity to optical injection and a number of applicatio
 ns based on self-mixing interferometry in diode lasers have been demonstra
 ted [1]. However\, the relatively large spectral width of diode lasers is 
 a limiting factor in high resolution measurements. On the other hand\, gas
  lasers having a narrower linewidth and a prospective higher signal-to-noi
 se ratio are restricted to the very weak feedback regime because of the hi
 gh reflectivity of their output coupler mirror and poor efficiency [2].\n\
 nDistinctively\, Quantum Cascade Lasers (QCLs) promise to merge the opport
 unity offered by the two types of laser in terms of spectral purity [3]\, 
 narrow intrinsic linewidth [4]\, and high quantum efficiency [5]. Also\, Q
 CLs are the most reliable light sources for feedback interferometric sensi
 ng across the mid-infrared and Terahertz (THz) region of the electromagnet
 ic spectrum\, due to the high output power levels over a wide range (1–5
  THz and 15–100 THz) of operating wavelengths. Moreover\, QCLs show an i
 ntrinsic stability of the continuous-wave emission in the presence of opti
 cal re-injection\, tolerating strong optical feedback levels without exhib
 iting dynamical instabilities such as mode-hopping\, intensity pulsation\,
  or coherence collapse [6]. This unique behaviour of QCLs can be ascribed 
 to the high value of the photon to carrier lifetime ratio (i.e.\, to an ul
 trafast electron relaxation time in the excited subbands) and to the negli
 gible linewidth enhancement factor. Innovative sensing applications attain
 ed by coherently interfering the QCL radiation into the optical cavity wil
 l be discussed\, spanning from free-carrier density imaging in semiconduct
 ors\, detecting a variety of kinetic entities\, characterizing laser param
 eters and optically induced THz metamaterials.\n\n[1] D. M. Kane and K. A.
  Shore\, Unlocking Dynamical Diversity—Optical Feedback Effects on Semic
 onductor Diode Lasers (John Wiley and Sons\, 2005).\n[2] S. Donati\, J. Ap
 pl. Phys. 49(2)\, 495–497 (1978).\n[3] S. Bartalini\, S. Borri\, P. Canc
 io\, A. Castrillo\, I. Galli\, G. Giusfredi\, D. Mazzotti\, L. Gianfrani\,
  and P. De Natale\, Phys. Rev. Lett. 104\, 083904 (2010).\n[4]M. S. Vitiel
 lo\, L. Consolino\, S. Bartalini\, A. Taschin\, A. Tredicucci\, M. Ingusci
 o\, and P. De Natale\, Nat. Photonics 6(8)\, 525–528 (2012).\n[5]M. Raze
 ghi\, S. Slivken\, Y. Bai\, B. Gokden\, and S. Ramezani Darvish\, New J. P
 hys. 11\, 125017 (2009).\n[6]F. P. Mezzapesa\, L. L. Columbo\, M. Brambill
 a\, M. Dabbicco\, S. Borri\, M.S. Vitiello\, H. E. Beere\, D. A. Ritchie\,
  and G. Scamarcio\, Opt. Express\n21(11)\, 13748–13757 (2013).\n
LOCATION:Mott Seminar Room (Mott Building Room 531)\, Cavendish Laboratory
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