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SUMMARY:Superconducting Photonics and Quantum Electronics - Dr Kaveh Delfa
 nazari\, University of Cambridge
DTSTART:20160222T141500Z
DTEND:20160222T151500Z
UID:TALK64513@talks.cam.ac.uk
CONTACT:Teri Bartlett
DESCRIPTION:Superconducting Photonics and Quantum Electronics\n\nDr. Kaveh
  Delfanazari 1\,2 \n\n1 Electrical Engineering Division and 2 Semiconducto
 r Physics Group\, Cavendish Laboratory\, University of Cambridge.\n\nIn th
 is talk\, I will present our recent research results on 1) Plasmonic Super
 conducting Metamaterials at Optical Wavelengths\, and 2) Superconducting Q
 uantum Electronics and THz Photonics:\n\n1) Superconductors with strongly 
 tunable superfluid plasma frequency\, zero dc and low transient frequency 
 losses present an opportunity for achieving metamaterials with extreme non
 linearity and tunability. To date all demonstration of these superconducti
 ng metamaterials have been reported in microwave\, millimetre and THz wave
 s. The response of such metamaterials has been tuned with incident light\,
  magnetic fields\, electrical current and temperature. \nI discuss the exp
 erimental observation of resonant response in the Niobium (Nb) superconduc
 ting metamaterial operating at optical wavelengths\, i.e. above the superc
 onducting gap. Our results show that\, contrary to common wisdom\, the ext
 reme sensitivity of superconducting state to external perturbations\, can 
 be accessed in the optical range\, thus paving the way for highly tunable 
 optical metamaterials and plasmonic devices based on superconductors [1\,2
 ].\n\n2) The intrinsic Josephson junctions (IJJs) in the high-Tc supercond
 uctor Bi2Sr2CaCu2O8+δ (Bi2212) are shown to have great potential for the 
 construction of an oscillator emitting in the terahertz (THz) frequency re
 gime. Single crystalline Bi2212 behaves as a stack of intrinsic Josephson 
 junctions (IJJs)\, and has a large superconducting energy gap (100 meV).  
 Bi2212 can generate EM waves with frequencies in the THz range (potentiall
 y between 0.3 and 15 THz) by the application of a dc-voltage V across the 
 N active IJJs\, each 1.533 nm thick\, stacked along the c-axis of the mesa
 \, with emission frequency f satisfying the quantum ac-Josephson relation 
 f = fJ = (2e/h)V/N= 483.597891 GHz for V/N= 1 mV\, where e is the electric
  charge and h is Planck’s constant.  Although IJJ mesas are small in siz
 e\, ~100 um across and ~1 um thick\, they can generate high power THz wave
 s at ~30 uW and the power generated by a three-mesa array was reported to 
 be 610 uW. Thus\, the IJJ-based THz emitter is one of the promising candid
 ates to fill the THz gap with a compact\, continuous-wave\, active quantum
  solid state source. Advances that could lead to portable\, battery-operat
 ed quantum THz devices will be discussed [3\,4]. \n\nReferences:\n1)	K. De
 lfanazari\, et al.\, and N. Zheludev\, to be submitted.\n2)	R. Singh and N
 . Zheludev\, Nat. Photonics\, 8\, 679 (2014).\n3)	K. Delfanazari\, et al. 
 IEEE Tran. THz Sci. and Technol. 5 (3) 505-511 (2015).\n4)	U. Welp\, et al
 . Nat. Photonics\, 7\, 702 (2013). \n\n
LOCATION:Mott Seminar Room (Mott Building Room 531)\, Cavendish Laboratory
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