Nhng tin b trong Quang hc, Quang ph và ng dng VI ISSN 1859 - 4271
Nhng tin b trong Quang hc, Quang ph và ng dng VI ISSN 1859 - 4271
Nhng tin b trong Quang hc, Quang ph và ng dng VI ISSN 1859 - 4271
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Advances in Optics, Photonics, Spectroscopy & Applications <strong>VI</strong> <strong>ISSN</strong> <strong>1859</strong> - <strong>4271</strong>efficiency of spontaneous emission into each direction of the nanofiber guided-modes. Diameterof nanofiber is chosen to satisfy a condition of k0a=1.45, where k0 is the free-space propagationconstant and a is the radius of the nanofiber. Condition of k0a=1.45 is the optimum condition forcoupli<strong>ng</strong> the fluorescence into the guided mode [4]. One can see that the nanofiber can collectfluorescence <stro<strong>ng</strong>>ph</stro<strong>ng</strong>>otons very efficiently. For atoms on the nanofiber surface, 11 % of thefluorescence <stro<strong>ng</strong>>ph</stro<strong>ng</strong>>otons are channeled into each side of the guided mode, and for atoms at oneradius away from the surface it is still 3 %.(a)(b)Fig. 1: a) Conceptual diagram of the scheme. The nanofiber locates at the mid oftapered optical fiber. b) Coupli<strong>ng</strong> efficiency of spontaneous emission into eachdirection of nanofiber propagation mode, η g , versus atom position r/a, where r and aare distance from nanofiber axis and radius of nanofiber, respectively.III. ATOMS ON A NANOFIBERAs quantum emitters, we use laser-cooled Cs-atoms and CdSeTe nanocrystal quantum-dots.Here, we describe the results on Cs-atoms. Experimental setup is sketched in Fig. 2.Fig. 2: Schematics for <stro<strong>ng</strong>>ph</stro<strong>ng</strong>>oton –correlation measurements.Cold atom cloud is overlapped to the nanofiber, and the atoms are excited by a probe laserbeam which is focused to the nanofiber. Fluorescence <stro<strong>ng</strong>>ph</stro<strong>ng</strong>>otons which are emitted into the fibermode are detected by two avalanche <stro<strong>ng</strong>>ph</stro<strong>ng</strong>>otodiodes APD1 and APD2, and <stro<strong>ng</strong>>ph</stro<strong>ng</strong>>oton coincidences attwo APDs are measured. Results are shown in the left column of Fig. 3. Right column exhibitsthe coincidences measured for <stro<strong>ng</strong>>ph</stro<strong>ng</strong>>otons emitted to both sides of the fiber. Parameter Ib denotesthe heater current to generate Cs-atoms.14