Resonance fluorescence of single molecules assisted by a plasmonic structure

Abstract

The resonance fluorescence of a two-level single molecular system interacting with a plasmonic nanostructure is investigated. Specific regions of space are identified, where a balance exists between the near-field enhancement and the modification of the decay rate, such that the fluorescence spectrum of the molecule exhibits the Mollow triplet and the emission photons are antibunched. The utilization of such quantum phenomena at the vicinity of custom-designed plasmonic nanostructures paves the way for applications in nanoscale quantum devices and quantum information processing. DOI: 10.1103/PhysRevB.81.193103 PACS number͑s͒: 82.37.Vb, 73.20.Mf, 78.67.Bf The interference of resonant transitions between atomic levels leads to many interesting quantum effects: Mollow absorption and triplet peaks, 1 electromagnetically induced transparency, 2 lasing without inversion, 3 quantum switching, 4 and spontaneous-emission cancellation.5 These effects are also exhibited by molecular systems. 6-9 For example, photon antibunching was observed in the fluorescence spectrum of pentacene molecules trapped in a solid. Autler-Townes structures were reported in pump-probe experiments of single terrylene molecules at superfluid helium temperature.8 Mollow fluorescence triplet and coherent oscillations of emission photons were observed at low temperature T = 1.4 K by strongly focusing the far-field excitation onto the extinction area of molecules. 9 In this work, instead of using far-field illumination, we utilize the dramatic nearfield enhancement provided at the vicinity of plasmonic structures to realize the strong coupling between single molecules and fields. Although molecules with complex vibration energy structures have a comparatively broad emission spectrum, the two-level approximation is perfectly well suited to describe them and has been widely used in the literature.7-9 We shall use this framework for this study. When a quantum emitter is approaching a resonant plasmonic structure, it experiences a strong near-field enhancement as well as a significant modification of the decay rate of its transition channels. 10 This modification of the population of excited state and decay rate can control the emission of fluorescent molecules and semiconductor quantum dots. 11Scanning near-field optical microscope probing of singlemolecule fluorescence indicates that near-field enhancement of resonant metallic nanoparticle leads to a change in intensity, lifetime, and spectrum of the fluorescence.12-14 Fluorescence quenching of dye molecules 15 and changes in the shape of fluorescence spectra 16 near gold nanoparticles have also been observed. When a single molecule is approaching a gold nanoparticle, a continuous transition from fluorescence enhancement to quenching is observed experimentally.12 Recently, the emission direction of a single molecule was experimentally realized by coupling the molecule to a specifically designed nanoantenna. 17Surface-dressed Bloch equations were furthermore used to study the fluorescence properties...

Surface-Plasmon-Induced Modification on the Spontaneous Emission Spectrum via Subwavelength-Confined Anisotropic Purcell Factor

“…33,48 In the following, we will see that the x-and z-direction have different Purcell factors 14 Γ xx /γ 0 and Γ xx /γ 0 , which has guaranteed the quantum interference effects of spectral line width narrowing and widening of spontaneous emission. The spontaneous emission spectra…”

“…It is known that large anisotropy of the Purcell factor only exists at about 30−120 nm nanoregions around the metallic nanostructures. 33 When single atoms are placed within the xy-plane 40 nm from the gold surface, significant interference effects in the spontaneous spectrum are observed. Here, the electric fields associated with Rabi frequencies is normalized by 2 and the center point or point 0 is at (0,0) nm.…”

Resonance fluorescence spectrum of aΛ-type quantum emitter close to a metallic nanoparticle

“…The ultracompact optical mode volume achieved in plasmon nanostructures leads to a large resonant enhancement of the local field near the MNP [1][2][3][4], as well as the modification of spontaneous emission rates of the emitter's optical transitions [5][6][7][8][9][10][11]. The exciton-plasmon coupling has received a great deal of attention leading to interesting phenomena like changes in photoluminescence lifetimes [12], in photon statistics [13], in the resonance fluorescence [14][15][16][17][18][19], in plasmon-induced quantum interference effects [20][21][22], in the control over population dynamics [23][24][25][26], and over nonlinear optical processes [27][28][29][30][31][32][33][34].…”

Resonance fluorescence spectrum of ap-doped quantum dot coupled to a metallic nanoparticle

“…By analogy with photoluminiscence, the resonance fluorescence of a QD near the plasmonic nanostructure must also be influenced by the modified incident electromagnetic field and by the modified radiative decay rate of the QD. Very recently, resonance fluorescence assisted by plasmonic structures have been addressed for two level atoms in CW regime [29,30] and under pulsed excitation [15].…”