Nano-antenne plasmonique pour l'émission de photons uniques

Transcription

1 Nano-antenne plasmonique pour l'émission de photons uniques JJ Greffet LCF, Institut d Optique, Institut Universitaire de France This work has been supported by the Agence Nationale de la Recherche, RTRA Triangle de la Physique, C nano Ile de France.

2 Co-Auteurs B. Habert, F. Bigourdan, F. Marquier, J-P. Hugonin, M. Laroche, R Esteban. C. Belacel, S. Michaelis de Vasconcellos, X. Lafosse, P. Senellart L. Coolen, C. Schwob, A. Maître C. Javaux, B. Dubertret 2

3 Goal of an antenna Increase the coupling between : a localized source/detector and propagating waves 3

4 Goal of an antenna for single photon emission Reduce the decay time Collect all the emitted photons 4

5 Nanoantennas Mühlschlegel et al. Science 308 p 1607 (2005) Kühn et al. PRL 97, (2006) Farahani et al., PRL 95, (2005) Anger et al., PRL 96, (2006) 5

6 What is a plasmon? Exemple : thin metallic film collective oscillation mode of the electrons w p 2 = ne2 me 0 m x = -ee - gm x = -n e2 e 0 x - gm x 6

7 Qu est-ce qu un plasmon de surface? E 0 exp ikx - igz- iwt [ ] r F = e 2 k z1 -e 1 k z2 e 2 k z1 + e 1 k z2 e a = 4pa 3 m w e m w ( ) -1 ( ) + 2 e 2 k z1 + e 1 k z2 = 0 e m ( w) + 2 = 0 7

8 Tuning the electrostatic resonance 8

9 Image d un plasmon de surface E x exp ikx - igz- iwt [ ] 9

10 Seeing Surface plasmons D Courtesy: Alexandre Bouhelier

11 Controlling the direction (1) 11

12 Controlling the direction (2) Key idea : no Purcell effect but funneling the energy into a single mode Broad spectrum and good coupling. 12

13 Motivation Design and fabricate deterministically a plasmonic antenna in order to - accelerate spontaneous emission, - control the angular emission over a broad band. 13

14 Surface plasmon microcavity Emission mechanism Phys.Rev.Lett. 104, (2010) 14

15 Surface plasmon microcavity R=600 nm Silver disk Embedded in glass Phys.Rev.Lett. 104, (2010) 15

16 Purcell factor Patch Antenna z emitters y 20 nm thick gold disk x 1-2 µm 200 nm gold 30 nm silica F^ Diameter (µm) F // centered 50 nm off center 80 Diameter 1.5 µm Belacel et al. NanoLetters 13, p 1516 (2013) 16

17 Quantum dots characterization CdSe/CdS quantum dots core diameter: 3 nm QD diameter : 13 nm 87% photons emitted in bright state, 13% In the grey state. Belacel et al. NanoLetters 13, p 1516 (2013) 17

18 Patch Antenna Fabrication Collaboration with Attocube (now commercially available) 18

19 Controlling the angular emission a centered 50 nm off center b Belacel et al. NanoLetters 13, p 1516 (2013) 19

20 Fluorescence Intensity Accelerating spontaneous Emission a b c d 0.01 Antenna Reference 1E Time(ns) Belacel et al. NanoLetters 13, p 1516 (2013) 20

21 Origin of the Purcell fluctuations The QD cluster thickness fluctuates. b 21

22 Quenching or photon emission? 22

23 Quenching or SPP emission? Photon (5%) Excited QD Antenna modes spontaneous emission Quenching 5% Joule losses d 23

24 Efficiency i) Current efficiency : <5% ii) Going to NIR (1.3 µm) and reducing the antenna size (0.32 µm), the efficiency increases to 42%. iii) Further improvement of the antenna design using metallodielectric structures can provide over 80% efficiency. 24

25 Key issue Can we unify our description of the electron/photon interaction? 25

26 Emission figures of merit Antennas Nanoantenna Microcavity I V Z, G R, NR F P, R Impedance Radiation resistance Classical dipole radiation No feedback on the source Fermi golden rule LDOS 26

27 Antenna impedance 27

28 Nanoantenna Impedance definition P = 1 2 Re [ iwp E *] z z P = 1 2 Re[ ] IU* - E z U i p Z -i p z I Greffet et al. Phys.Rev.Lett. 105, (2010) 28

29 Nanoantenna Impedance definition P = 1 2 Re [ iwp E *] z z P = 1 2 Re[ ] IU* - E z U i p Z -i p z I E z = G zz p z U=ZI Greffet et al. Phys.Rev.Lett. 105, (2010) 29

30 Nanoantenna Impedance definition P = 1 2 Re [ iwp E *] z z P = 1 2 Re[ ] IU* -E z U i p Z -i p z I é -E z = G ù zz ë ê iw û ú -iwp z ( ) U=ZI Z = G ( r,r ) zz iw Greffet et al. Phys.Rev.Lett. 105, (2010) 30

31 Physical meaning of Re(Z) Electrical engineering point of view : Radiation resistance Im(G) Quantum optics point of view : LDOS Im(G) P = 1 2 Re [ iwp E *] z z 31

32 Microcavity versus nanoantenna Spatial confinment ( /2n ) 3 z 6 /a 3 Quality factor Broadband Waves K < n /c Evanescent waves/ polaritons 32

33 Source-antenna coupling Antennas Nanoantenna I V Z, G R, NR Impedance matching Multiple scattering 33

34 Quantum emitter impedance What is the internal impedance of a quantum emitter? p z = 0 E z -i p z = (-i 0 )(E z ) Greffet et al. Phys.Rev.Lett. 105, (2010) 34

35 Atom : a RLC series circuit! Two-level system polarisability (without the rotating wave approximation) Greffet et al. Phys.Rev.Lett. 105, (2010) 35

36 Addition d impédances et diffusion multiple Addition d impédances Diffusion multiple 36

37 Example 1: a microcavity G zz (r,r',w) = E z (r)e z * (r') w 0 2 (1- i /Q) -w 2 w 2 e 0 1 Z = iw G zz r,r ( ) = 1 R + i æ Cw - 1 ö ç è Lw ø C= 0 V eff 1/L= 0 V eff 0 2 R = QL Microcavity = RLC parallel circuit = notch filter 37

38 Example 2: a metallic nanosphere F p = Im(G) Im(G 0 ) =1+ 6p e 0 c 3 w 3 Im[ u S( r,r,w)u] F p =1+ 3Q a3 l 3 4p 2 p z 6 E( r,w) = G 0 ( r,r,w)p+ S( r,r,w)p V eff = p z6 a 3 The nanoantenna achieves a large Purcell factor over a broad spectrum Greffet et al. Phys.Rev.Lett. 105, (2010) 38

39 Summary Z = G zz r,r ( ) iw 39