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SUMMARY:Ultrabright solid state sources of quantum light - Pascale Senella
 rt (CNRS/LPN)
DTSTART:20110307T113000Z
DTEND:20110307T123000Z
UID:TALK29995@talks.cam.ac.uk
CONTACT:6270
DESCRIPTION:Ultrabright solid state sources of quantum light\nPascale Sene
 llart.\nLaboratoire de Photonique et de Nanostructures\, CNRS\, Marcoussis
 \nA semiconductor quantum dot (QD) is a promising system to achieve a sour
 ce of single photons or of\nentangled photon pairs. The main advantage of 
 QD based sources over attenuated classical sources is\nthe possibility to 
 generate exactly one photon for each excitation pulse. However\, to be of 
 practical\nvalue\, one needs to efficiently extract and collect the photon
 s emitted by the QD.\nAccelerating the QD spontaneous (Purcell effect) is 
 a way to make sure that the photons emitted by\nthe QD are funnelled into 
 a cavity mode. This idea has motivated many works to fabricate coupled\nQD
 -cavity devices. For the last few years\, the main challenge has been to c
 ontrol both the spectral\nand spatial matching between a single QD and a c
 avity mode. We have developed an in-situ\nlithography technique that allow
 s deterministically coupling a single QD to a pillar cavity mode1 and\nto 
 fabricate bright single photon sources.\nUsing the same technique\, we rec
 ently fabricated a bright single photon source by coupling a QD to a\nconf
 ined hybrid photon-plasmon mode. We show that discrete optical modes can b
 e obtained simply\nby depositing a 50 nm thick microdisk of gold on an int
 erferential mirror (fig a). The field is confined\nat the interface with t
 he metal\, below the disk area\, with no further processing needed. A four
 -fold\nacceleration of spontaneous emission into the mode together with a 
 ten-fold inhibition of emission in\nall other mode ensures efficient funne
 lling of the quantum dot emission into the optical mode\nThe radiative rec
 ombination of two electron-hole pairs trapped in a QD can also lead to the
  emission\nof entangled photon pairs2. Extracting polarization entangled p
 hoton pairs requires achieving\nsimultaneous Purcell effect for both optic
 al transitions of the QD as well as gathering several\nconditions to make 
 sure that the Purcell effect is not detrimental to the entanglement. We sh
 ow that a\nphotonic molecule consisting in two coupled identical pillars g
 athers all these requirements. By\ndeterministically inserting a single QD
  into a photonic molecule\, we fabricate the brightest source of\nentangle
 d photon pairs to date. We also show that the Purcell effect allows increa
 sing the degree of\nentanglement of the photon pairs.\n[1] A. Dousse et al
 .\, Phys. Rev. Lett. 101\, 267404 (2008)\n[2] A. Dousse et al\, Nature 466
 \, 217 (2010).\na: Electric field of a 0D confined photon-plasmon mode obt
 ained by depositing a 50 nm gold disk on an\nBragg reflector. b: SEM image
  of a photonic molecule. c: Real part of the density matrix of the two-pho
 ton\nstate measured on a molecule at 5 K.\na) b)
LOCATION:Ryle Seminar Room\, Rutherford Building\, Cavendish Laboratory
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