OSA's Digital Library

Optics Express

Optics Express

  • Editor: Andrew M. Weiner
  • Vol. 21, Iss. 5 — Mar. 11, 2013
  • pp: 5643–5653
« Show journal navigation

Coherently-enabled environmental control of optics and energy transfer pathways of hybrid quantum dot-metallic nanoparticle systems

Ali Hatef, Seyed M. Sadeghi, Simon Fortin-Deschênes, Etienne Boulais, and Michel Meunier  »View Author Affiliations


Optics Express, Vol. 21, Issue 5, pp. 5643-5653 (2013)
http://dx.doi.org/10.1364/OE.21.005643


View Full Text Article

Acrobat PDF (1177 KB)





Browse Journals / Lookup Meetings

Browse by Journal and Year


   


Lookup Conference Papers

Close Browse Journals / Lookup Meetings

Article Tools

Share
Citations

Abstract

It is well-known that optical properties of semiconductor quantum dots can be controlled using optical cavities or near fields of localized surface plasmon resonances (LSPRs) of metallic nanoparticles. In this paper we study the optics, energy transfer pathways, and exciton states of quantum dots when they are influenced by the near fields associated with plasmonic meta-resonances. Such resonances are formed via coherent coupling of excitons and LSPRs when the quantum dots are close to metallic nanorods and driven by a laser beam. Our results suggest an unprecedented sensitivity to the refractive index of the environment, causing significant spectral changes in the Förster resonance energy transfer from the quantum dots to the nanorods and in exciton transition energies. We demonstrate that when a quantum dot-metallic nanorod system is close to its plasmonic meta-resonance, we can adjust the refractive index to: (i) control the frequency range where the energy transfer from the quantum dot to the metallic nanorod is inhibited, (ii) manipulate the exciton transition energy shift of the quantum dot, and (iii) disengage the quantum dot from the metallic nanoparticle and laser field. Our results show that near meta-resonances the spectral forms of energy transfer and exciton energy shifts are strongly correlated to each other.

© 2013 OSA

1. Introduction

Manipulation of the optical properties of semiconductor quantum dots (QDs) as efficient emitters has a broad range of applications in electro-optic devices such as high-efficiency single photon sources [1

1. M. Toishi, D. Englund, A. Faraon, and J. Vucković, “High-brightness single photon source from a quantum dot in a directional-emission nanocavity,” Opt. Express 17(17), 14618–14626 (2009). [CrossRef] [PubMed]

], quantum information processors [2

2. I. Fushman, D. Englund, A. Faraon, N. Stoltz, P. Petroff, and J. Vučković, “Controlled phase shifts with a single quantum dot,” Science 320(5877), 769–772 (2008). [CrossRef] [PubMed]

], light emitting devices [3

3. V. Wood and V. Bulović, “Colloidal quantum dot light-emitting devices,” Nano Rev 1(0), 5202 (2010). [CrossRef] [PubMed]

], photovoltaic cells [4

4. J. Chandrasekaran, D. Nithyaprakash, K. B. Ajjan, S. Maruthamuthu, D. Manoharan, and S. Kumar, “Hybrid solar cell based on blending of organic and inorganic materials—An overview,” Renew. Sustain. Energy Rev. 15(2), 1228–1238 (2011). [CrossRef]

] and biological applications [5

5. S. J. Rosenthal, J. C. Chang, O. Kovtun, J. R. McBride, and I. D. Tomlinson, “Biocompatible quantum dots for biological applications,” Chem. Biol. 18(1), 10–24 (2011). [CrossRef] [PubMed]

]. In many of these applications the interaction between an excited QD and the surrounding environment can be controlled by using different reservoirs such as optical microresonators [6

6. S. Pang, R. E. Beckham, and K. E. Meissner, “Quantum dot-embedded microspheres for remote refractive index sensing,” Appl. Phys. Lett. 92(22), 221108 (2008). [CrossRef] [PubMed]

] or photonic crystal nano cavities [7

7. T. Nakamura, T. Asano, K. Kojima, T. Kojima, and S. Noda, “Controlling the emission of quantum dots embedded in photonic crystal nanocavity by manipulating Q-factor and detuning,” Phys. Rev. B 84(24), 245309 (2011). [CrossRef]

, 8

8. K. Hennessy, A. Badolato, M. Winger, D. Gerace, M. Atatüre, S. Gulde, S. Fält, E. L. Hu, and A. Imamoğlu, “Quantum nature of a strongly coupled single quantum dot-cavity system,” Nature 445(7130), 896–899 (2007). [CrossRef] [PubMed]

]. The size of these reservoirs has an inherent limitation, as their size have to be at least half the wavelength of the incident field. On the other hand, localized surface plasmon resonances (LSPRs) of metallic nanoparticles (MNPs) can amplify and localize the electromagnetic fields in nanometer length scales, much smaller than the diffraction limit of light. As a result, MNPs have merged as a viable alternative to control electronic and optical properties of QDs at the nanoscale [9

9. M. Achermann, “Exciton-plasmon interactions in metal-semiconductor nanostructures,” J. Phys. Chem. Lett. 1(19), 2837–2843 (2010). [CrossRef]

]. This allows combining the sub-wavelength feature offered by plasmons with the efficient emission characteristic of QDs for the design of novel optical systems such as plasmonic lasers [10

10. R. F. Oulton, V. J. Sorger, T. Zentgraf, R.-M. Ma, C. Gladden, L. Dai, G. Bartal, and X. Zhang, “Plasmon lasers at deep subwavelength scale,” Nature 461(7264), 629–632 (2009). [CrossRef] [PubMed]

] and fluorescence-based sensors [11

11. J. Lee, P. Hernandez, J. Lee, A. O. Govorov, and N. A. Kotov, “Exciton-plasmon interactions in molecular spring assemblies of nanowires and wavelength-based protein detection,” Nat. Mater. 6(4), 291–295 (2007). [CrossRef] [PubMed]

].

In the above-mentioned studies, QDs were influenced by the intrinsic resonances of the cavities or LSPRs. The prime feature of such resonances is that they are not influenced by the QDs, except perhaps for second order changes caused by perturbation of the dielectric constant. Recent investigations have shown, however, that when a QD is in the vicinity of a MNP and driven by a coherent light source (a laser field), the combined system supports molecular-like collective resonances, different from LSPRs. Such resonances, called Plasmonic Meta Resonance (PMR) [12

12. S. M. Sadeghi, “Plasmonic metaresonances: Molecular resonances in quantum dot-metallic nanoparticle conjugates,” Phys. Rev. B 79(23), 233309 (2009). [CrossRef]

], are associated with the coherent exciton-plasmon coupling in the QD-MNP system formed via the quantum coherence generated in the QD by the laser field. When a QD-MNP system is close to its PMR, the near field of the MNP (coherent-plasmonic field) can become significantly stronger than its LSPR, and the optics and dynamics of the QDs become strongly sensitive to the structural parameters of the system, the intensity of the incident laser field, and the dielectric constant of the environment [13

13. A. Hatef, S. M. Sadeghi, and M. R. Singh, “Coherent molecular resonances in quantum dot-metallic nanoparticle systems: coherent self-renormalization and structural effects,” Nanotechnology 23(20), 205203 (2012). [CrossRef] [PubMed]

, 14

14. S. M. Sadeghi, “Plasmonic metaresonance nanosensors: Ultrasensitive tunable optical sensors based on nanoparticle molecules,” IEEE Trans. Nanobioscience 10, 566–571 (2011).

].

The main objective of this paper is to study how the nature of the optical responses of QDs, their excitonic states, and energy transfer pathways can be distinctively determined by the dielectric constant of the environment in the presence of quantum coherence. For this, instead of using optical fields of cavities or intrinsic plasmonic fields of MNPs, we study QDs in coherent-plasmonic fields associated with PMR. Our system consists of a QD conjugated to a gold nanorod (AuNR) in the form of to-the-side configuration and is driven by a laser field (See Fig. 1(a)
Fig. 1 (a) Schematic representation of the hybrid system (QD–AuNR) unit. The arrow on top shows the Förster resonance energy transfer (FRET) rate between QD and AuNR. The dipole-dipole coupling is due to an applied external field which induces a polarization on both the AuNR and the QD. The external (E) field is perpendicular to the QD-AuNR axis. (b) Schematic illustration of the two-level QD (left) upper excitonic (|2) and ground state (|1). The shaded area shows the energy band of the AuNR (right) where the dark strip shows the broden plasmon resonance energy peak. The transition energy of QD is matched with the resonance energy of Au nanorod.
).

Our results suggest that with minuscule changes in the refractive index of the environment, the optical and electronic (excitonic) transition of the QDs undergo unique and more dramatic changes, compared to the cases of the optical cavities or LSPRs. The results also show that such changes lead to unprecedented spectral modifications in the Förster resonance energy transfer (FRET) from the quantum dots to the nanorods. In particular, we demonstrate that when a QD-AuNR system is close to its PMR, we can adjust the refractive index of the environment to (i) control the frequency range where the energy transfer from the QD to the nanorod is inhibited, (ii) manipulate the exciton transition energy shift, causing blue or red shift, and (iii) disengage the QD from the nanorod and laser field. Our results suggest that in the presence of quantum coherence, the way energy is transferred to the metallic nanorods determines the spectral form of the exciton frequency shift. These results open up new possibilities for development of chemical and biological sensors and nanodevices based on the application of quantum coherence in nanoparticle systems.

2. Model and formalism

In this paper, we assume that the QD-AuNR hybrid is embedded in a background dielectric constant (εb) and is driven by a linearly polarized external electric field with an amplitude E0 and frequencyω(E(t)=12E(t)0eiωt). The laser light polarization is parallel to the AuNR longitudindal axis and perpendicular to the hybrid system axis, as shown in Fig. 1(a). We treat the AuNR classically and represent it as an ellipsoid (prolate spheroid) with a semi-major axis a and semi-minor axis b, where the corresponding aspect ratio is q = a/b [15

15. K.-S. Lee and M. A. El-Sayed, “Dependence of the enhanced optical scattering efficiency relative to that of absorption for gold metal nanorods on aspect ratio, size, end-cap shape, and medium refractive index,” J. Phys. Chem. B 109(43), 20331–20338 (2005). [CrossRef] [PubMed]

]. The response of the AuNR to the applied electric field is described by its frequency dependent scalar polarizability. The polarizability of the AuNR in the dipole approximation can be written as a frequency-dependent complex coefficient β(ω)=[εm(ω)εb]/[3εb+3κ(εm(ω)εb)] whereκ is called the depolarization factor of the AuNR, and εm(ω) is the dielectric constants of the AuNR. In our calculations, the amplitude of the incident electric field lies along the semi-major axis (a) and depolarization factor is given as
κ=1e2e2[12eln(1+e1e)1]
(1)
where e=11/q2 [16

16. H. C. Van de Hulst, Light Scattering by Small Particles (John Wiley & Sons, Inc., 1951).

]. Note that for a sphere, q approaches unity, the depolarization factor approaches 3 and the well known expression for the sphere polarizability is recovered. We treat the QD quantum mechanically in the density-matrix formalism as a two level system with exciton energy ω0 near the plasmonic peak of the AuNR (See Fig. 1(b)). The dipole moment and dielectric constant are μ and εs, respectively. Considering the presence of the AuNR and the induced polarization field, net field experienced by the QD can be written:
EQD=E02εeff[1ab2β(ω)R3]+ab2PQD4πε0μεeff2R6
(2)
where and R are the reduced factor and the center-to-center distance between the QD and AuNR, respectively. is the induced polarization of the QD expressed via the off-diagonal elements of the density matrix within the framework of the Maxwell-Bloch equations. Note that in Eq. (2) the first term shows the contribution of the external field, the second term arises from the induced polarization of the AuNR and the last term shows the effect of the QD self-action. Following the traditional approach of Weisskopf and Wigner [17

17. P. Michler, ed., Single Semiconductor Quantum Dots (Springer, 2009).

], we use the density matrix method to find the coherence terms ( and ) of the QD in the hybrid system. The rotating-wave approximation [18

18. O. Marlan, Scully and M. S. Zubairy, Quantum Optics (Cambridge, 1997).

] is used to derive all time-dependent density matrix elements describing the dynamic of the QD as following:
dΔρdt=Γ21(1+Δρ)+2i(Ω12rρ12Ω12*rρ21)
(3)
dρ21dt=(iΔ12+γ21)ρ21iΩ12rΔρ
(4)
In the above equations, Δρ=ρ11ρ22 is the population difference between the QD ground state and excited state,ρ12is the amplitude of the off-diagonal density matrix elements defined as ρ˜12=ρ12eiωt, and Γ21 and γ21 introduced above refer to energy and polarization relaxation rates of the isolated QD, respectively. Δ12=ω21ω is the detuning between the excitonic transition and the laser field energy (laser detuning parameter). Here, Ω12r=μEQD/2 is the normalized Rabi frequency given by Ω12r=Ω12eff+ηρ21, where Ω12eff=Ω120(1β(ω)ab2/R3) in which Ω120=μE0/2εeff refers to the Rabi frequency of the bare external field when the QD is isolated (very large R). The η term is a complex Lorentzian function that including all the information on the QD self-feedback in dipole-dipole approximation and is given by [19

19. J.-Y. Yan, W. Zhang, S. Duan, X.-G. Zhao, and A. O. Govorov, “Optical properties of coupled metal-semiconductor and metal-molecule nanocrystal complexes: Role of multipole effects,” Phys. Rev. B 77(16), 165301 (2008). [CrossRef]

]:
η=ab2β(ω)μ/4πε0εbεeff2R6
(5)
Knowing the total normalized Rabi frequency, one can define the coherent–plasmonic field enhancement (CPFE) factor:
Pzcoh(ω)=|Ω12rΩ120|2
(6)
Pzcoh(ω) represents the ratio of the effective field intensity at the location of the QD in the presence of AuNR to that in the absence of it. Equation (6) clearly indicates that when coherent-plasmonic effects are included, the CPFE depends on the frequency and intensity of the exciting field. Note that the intensity plays a key role to put the QD-AuNR hybrid system on the verge of PMR [14

14. S. M. Sadeghi, “Plasmonic metaresonance nanosensors: Ultrasensitive tunable optical sensors based on nanoparticle molecules,” IEEE Trans. Nanobioscience 10, 566–571 (2011).

].

To explicit the effect of exciton-plasmon interaction on the energy-transfer efficiency between the nanoparticles (QD and AuNR), as well as the exciton resonance energy shift, Eq. (4) can be written as:
dρ21dt=[i(Π12ω)+Λ21)]ρ21iΩ12effΔρ
(7)
Comparing Eq. (7) to Eq. (4) shows the effect of the QD self-feedback (η term) on the QD resonance energy and the dipole dephasing rate. In Eq. (7), Π12=ω21ηrΔρis the normalized energy of the exciton transition and Λ21=γ21+ηImΔρ is the Förster enhanced broadening of this transition (normalized dipole dephasing rate) where ηIm=Im(η) and ηRe=Re(η). Since the normalized exciton transition energy (Π12) depends on the sign ofηrΔρ, we expect to see a red or a blue shift in the exciton transition energy spectrum of the QD when the sign of ηrΔρ changes.

3. Results and discussion

In our calculations, the aspect ratio of AuNR is taken to be q = 4 where its minor radius is b = 5 nm. For this geometry a maximum field enhancement created near the tips of the rod in the near infrared (NIR) region at ω0 = 1.6 eV (λ = 775 nm) energy. The dielectric constant of AuNR is taken to be εm = −22.3 + 1.39i which is the bulk dielectric constant for gold as found experimentally at the given energy [20

20. P. B. Johnson and R. W. Christy, “Optical constants of the noble metals,” Phys. Rev. B 6(12), 4370–4379 (1972). [CrossRef]

]. For AuNR of such a size, recent calculations have shown that the influence of the particle size on the dielectric constant is negligible. For example, in ref [21

21. A. Trügler and U. Hohenester, “Strong coupling between a metallic nanoparticle and a single molecule,” Phys. Rev. B 77(11), 115403 (2008). [CrossRef]

], it is shown that in an AuNR the scattered spectrum and the incident laser energy have a peak at the same energy for both the experimental bulk dielectric constant and the Drude model based theoretical dielectric constant including all the corrections regarding the size and the shape of the AuNR. Also in ref [22

22. J. A. Scholl, A. L. Koh, and J. A. Dionne, “Quantum plasmon resonances of individual metallic nanoparticles,” Nature 483(7390), 421–427 (2012). [CrossRef] [PubMed]

]. it is shown that the difference between the value of the dielectric constant of the bulk and the nanosized metallic particles becomes only significant for particles smaller than 10 nm. The reference dielectric constant of the background material is εb = 1.80 (like water). In Fig. 2(a)
Fig. 2 (a) The maximum filed enhancement on the tips of a prolate spheroid versus the aspect ratio (q) and the incident laser energy, (b) Cross-section of the electric field enhancement distribution in and around a AuNR, for q = 4 when irradiated with a ω0 = 1.6eV ( = 775 nm) linearly polarized along the ellipsoid’s longitudinal axis. The legend on the right shows the values of the field enhancement.
we show the impact of q on the variation of the maximum field enhancement at the tips of AuNR versus incident laser energy. As shown in this figure by increasing q the maximum field enhancement increases and the peak energy shifts towards NIR region. Figure 2(b) shows the cross section of the electric field enhancement distribution in and around an AuNR for b = 5 nm and q = 4. In this figure, the right legend shows the value of normalized field enhancement. Note that for q less than 1 the maximum field enhancement decreases dramatically.

The QD can be considered as CdTe/CdS [23

23. Z. Deng, O. Schulz, S. Lin, B. Ding, X. Liu, X. Wei, R. Ros, H. Yan, and Y. Liu, “Aqueous synthesis of zinc blende CdTe/CdS magic-core/thick-shell tetrahedral-shaped nanocrystals with emission tunable to near-infrared,” J. Am. Chem. Soc. 132(16), 5592–5593 (2010). [CrossRef] [PubMed]

] which has an exciton resonance energy (ω0 = 1.6 eV) in the NIR region. The dielectric constant and dipole moment of the QD are taken as εs = 6 [24

24. R. D. Artuso, G. W. Bryant, A. Garcia-Etxarri, and J. Aizpurua, “Using local fields to tailor hybrid quantum-dot/metal nanoparticle systems,” Phys. Rev. B 83(23), 235406 (2011). [CrossRef]

], and μ = 0.7 e nm [25

25. P. Guyot-Sionnest, X. Peng, and D. Mingos, Intraband Spectroscopy and Semiconductor Nanocrystals Semiconductor Nanocrystals and Silicate Nanoparticles (Springer Berlin / Heidelberg, 2005), pp. 59–77.

], respectively. The typical values for the radiative decay rate and the dephasing width parameter are Γ21 = 1.25 ns−1 and γ21 = 2.7 ns−1, respectively [24

24. R. D. Artuso, G. W. Bryant, A. Garcia-Etxarri, and J. Aizpurua, “Using local fields to tailor hybrid quantum-dot/metal nanoparticle systems,” Phys. Rev. B 83(23), 235406 (2011). [CrossRef]

]. Here, one can consider the effects of the additional nonradiative rate by Ohmic losses in the environment assuming that the QD has a high intrinsic quantum yield [26

26. P. Anger, P. Bharadwaj, and L. Novotny, “Enhancement and Quenching of Single-Molecule Fluorescence,” Phys. Rev. Lett. 96(11), 113002 (2006). [CrossRef] [PubMed]

]. Also the effect of the geometrical properties of the gold nanoparticle on the radiative decay rate can be considered [13

13. A. Hatef, S. M. Sadeghi, and M. R. Singh, “Coherent molecular resonances in quantum dot-metallic nanoparticle systems: coherent self-renormalization and structural effects,” Nanotechnology 23(20), 205203 (2012). [CrossRef] [PubMed]

]. However, considering these additional terms in Eq. (3) and Eq. (4) has no significant impact on the results presented in this paper.

We set the laser intensity to be I = 64.3 W/cm2 to put the system on the verge of the PMR for the desired center-to-center distance between QD and AuNR (R ≈21 nm). Please note that here the quantum dot is treated as a dipole. However, the dimension of the system we used in calculation is reasonable in practice. In the case of CdTe/CdS, to obtain the NIR wavelength emission, the size of the QD is around 10 nm. If this is the case, the radius of the QD and the minor radius of AuNR are 5 nm, the surface to surface distance between the particles would be around 11 nm at which it is reasonable to see the exciton-plasmon effects.

To obtain the optical properties and exciton transition energy shift of the QD as well as the energy transfer rate between the nanoparticles, the coherence terms (ρ21andρ12) are obtained via solving Eq. (3) and Eq. (4) numerically in steady state.

To investigate optics and electronic (excitonic) states of the QD in the presence of the plasmonic field of the AuNR when it is normalized by quantum coherence, we start by reviewing PMR in the QD-AuNR hybrid system for to-the-side configuration. Figure 3
Fig. 3 The coherent–plasmonic field enhancement (CPFE) versus the background dielectric constant (εb) with I = 64.3 W/cm2 and R = 21 nm. The solid, dash-dotted and dotted curve shows Δ12 = 0, 5 and 10 ns−1, respectively. The dashed line shows the case when the particles are far from each other (R = 100 nm).
shows the results for the coherent–plasmonic field enhancement (CPFE) factor defined in Eq. (6) as a function of the background dielectric constant (εb). In this figure, for R = 21 nm, we calculate the CPFE for an interval of εb from 1.7 to 1.9. The solid, dash-dotted and the dotted curve show the CPFE for Δ12 = 0, 5 and 10 ns−1, respectively. Initially, depending on the values of Δ12, as εb increases, CPFE is suppressed (dark state) until εb approaches a certain value. Note that the dark state here is the sign of PMR. After this value CPFE raises abruptly reaching a maximum value (bright state). The rationale behind this is to show how these features in the CPFE profile in the QD-AuNR hybrid system not only supports the existence of PMR but also shows the existence of switching of the system when the dielectric constant of the background material changes slightly. In Fig. 3 we also show this process depends on the value of Δ12. For Δ12 = 0, 5 and 10 ns−1 the state transition from dark to bright happens for εb = 1.788 (solid line), 1.785 (dash-dotted line) and 1.765 (dotted line), respectively. In this figure, to show the impact of coherent exciton-plasmon coupling and the quantum coherence on CPFE in QD, we also consider the case where the center-to-center distance between QD and AuNR is large and therefore the effects of quantum coherence have vanished (bare QD). The dashed line in Fig. 3 shows that for this condition (R = 100 nm), CPFE is basically equal to unity, i.e., no significant field enhancement occurs.

It is worth mentioning, that in the absence of quantum coherence (or very large R), as seen in Fig. 2(b), the center of the AuNR is the nod point of plasmon polaritons. Therefore, at this point electromagnetic field enhancement is very weak. Under this condition, field enhancement at the tips of the AuNR is rather significant. Due to coherent exciton-plasmon coupling in the QD-AuNR system, however, our results show that the near field of the AuNR (coherent-plasmonic field) can become significantly stronger or weaker than bare AuNR, depending on the molecular states of QD-AuNR system. This allows efficient FRET from the QD to the AuNR.

As seen in Fig. 4(a) for Δ21 = 0 by decreasing R, ηReΔρ is zero until R approaches a certain value and then depends on the value of εb, the sign and the value of ηReΔρ changes. Here, for εb = 1.8, 1.825 and 1.85, ηReΔρ is positive (solid curve), zero (dash-dotted curve) and negative (dotted curve), respectively. In this calculation we show how a slight variation of εb can cause a switching in the form of a red and blue shift in the QD exciton energy. This bistable trend also is seen in the FRET rate. As shown in Fig. 4(b) for Δ21 = 0 by decreasing R, ηImΔρvanishes until R approaches a certain amount after that the energy exchange between the nanoparticles starts dramatically. Note that here the εb variations only change the critical values of R slightly and have no effect on the nature of the curves. In insets of Fig. 4(a) and Fig. 4(b), we show the off resonance laser situation where Δ21 = 600. As seen in these insets the variation of ηReΔρ and ηImΔρ is monotonic and there is no switching in their profile.

For dash-dotted curve where εb approaches 1.825, ηReΔρ flattens to almost zero. This means that in this particular value of εb≈1.825 there is no exciton energy shift and it has symmetry around Δ12=0. By further increasing εb, the ηReΔρ sign changes to negative and blue shift happens. For ηImΔρ as seen in Fig. 5(b) atΔ12=0, the FRET rate totally vanishes. However, by sweeping the laser frequency around the QD resonance energy this energy transfer rate increases dramatically and eventually flattens. An interesting result here is that by a slight change in εb the FRET rate can be narrowed or widened. These results show how the FRET rate between nanoparticles can be controlled by a slight modification of the system environment. In this figure the solid, dash-dotted and dotted curves show εb = 1.80, 1.825 and 1.85, respectively. Please note that the curves in Fig. 5(a) and Fig. 5(b) are in correlation. For example, forεb≈1.825 the exciton energy shift and FRET rate have symmetry around Δ12=0. Please note that the impact of such a small variation of the background dielectric constant on the QD exciton energy and AuNR plasmon resonance is negligible in our results. Also as shown in Fig. 1(b), compared to exciton energy of the QD, the energy spectrum of the AuNR at the LSPR is broad enough so that the exciton-plasmon coupling stays valid with such a small modification.

In the absence of AuNR, when the laser field is detuned around the QD transition, it can lead to blue or red AC Stark shift, depending on the detuning of the laser frequency from this transition. As the laser intensity increases the amount of the AC shift increases, while the spectra can be broadened to some extent (power broadening). The results shown in Fig. 5, however, were obtained with a given amount of the laser intensity, while we changed the refractive index of the environment. The results presented in Fig. 5(a) show unique shift caused by PMR when detuning is small. For larger detuning we see blue or red shift, depending on the value of the dielectric constant, while the frequency and intensity of the laser was kept unchanged. While AC shift played a limited role in our case, the transition shift caused by plasmonic effects is quite important. As a result, for a given Δ12 we can have red or blue shift or we can choose a dielectric constant such that any detuning of the laser field does not lead to any shift (dotted-dashed line in Fig. 5(a)). Another remarkable phenomenon seen in our calculations is the possibility to modify the nature of the QD’s optical properties by driving it with coherent laser in the vicinity of a AuNR. It is known that the real and imaginary part of the coherence terms (Re(ρ21) and Im(ρ21)) respectively, show the laser light dispersion (refractive index) and absorption by QD [17

17. P. Michler, ed., Single Semiconductor Quantum Dots (Springer, 2009).

]. For a bare QD, these quantities take the usual form of the real and imaginary part of a complex Lorentzian function. However, in a hybrid system, when the QD is placed in the vicinity of AuNR, the nature of these quantities changes dramatically. In Fig. 6(a)
Fig. 6 (a) The Re(ρ21) and (b) Im(ρ21) versus the laser detuning parameter (Δ21) The solid, dotted and the dashed curve shows εb = 1.8, 1.825 and 1.85, respectively. The insets show the same quantities for each case where for R = 100 nm, where the nano-particles are far from each other.
, the Re(ρ21) spectrum has one minimum and two maxima around Δ12=0. These curves show that the QD can become dispersive or non-dispersive by detuning the laser frequency. Also, slight εb modifications do not change the nature of the curves. By increasing and decreasingεb, the Re(ρ21) spectrum width broadens and narrows, respectively. It is also worth mentioning, that if the value of εb decreases, the dip in Re(ρ21) spectrum vanishes completely.

In Fig. 6(b), however, the sign of the Im(ρ21) spectrum changes at Δ12=0 where the negative values in this spectrum show a gain without inversion in the hybrid system [29

29. H. Hartmut and W. K. Stephan, Quantum Theory of The Optical And Electronic Properties Of Semiconductors (World Scientific, 2004).

]. Here, by increasing εb the extrema change causing more absorption and less gain. The insets in Fig. 6(a) and Fig. 6(b), also show the impact of exciton-plasmon interaction on Re(ρ21) and Im(ρ21) profile as a function of Δ12 where the particles are far from each other (R = 100 nm). As seen in these insets for a large value of R, Re(ρ21) and Im(ρ21) have the regular behavior as expected. At the end, in terms of the fabrication the single QD-AuNR systems can be formed, for example, by attaching an AuNR to an immobilized QD via a rigid polypeptide [30

30. T. Pons, I. L. Medintz, K. E. Sapsford, S. Higashiya, A. F. Grimes, D. S. English, and H. Mattoussi, “On the quenching of semiconductor quantum dot photoluminescence by proximal gold nanoparticles,” Nano Lett. 7(10), 3157–3164 (2007). [CrossRef] [PubMed]

, 31

31. I. L. Medintz, K. E. Sapsford, A. R. Clapp, T. Pons, S. Higashiya, J. T. Welch, and H. Mattoussi, “Designer variable repeat length polypeptides as scaffolds for surface immobilization of quantum dots,” J. Phys. Chem. B 110(22), 10683–10690 (2006). [CrossRef] [PubMed]

]. They can also be fabricated using e-beam lithography to fabricate AuNRs on a substrate and then conjugate them with colloidal QDs [32

32. J. M. Slocik, F. Tam, N. J. Halas, and R. R. Naik, “Peptide-assembled optically responsive nanoparticle complexes,” Nano Lett. 7(4), 1054–1058 (2007). [CrossRef] [PubMed]

]. The results presented in this paper may even be implemented using epitaxially grown QD–AuNR systems. Regarding this, one can use recent investigations of the fabrication of MNPs inside epitaxial structures, or the formation of epitaxially grown QDs very close to the surface [33

33. R. Kadono, W. Higemoto, K. Nagamine, and F. L. Pratt, “An atom in the bloch state,” Phys. Rev. Lett. 83(5), 987–990 (1999). [CrossRef]

]. Such techniques provide us with QD-AuNR hybrids with well-defined orientations, allowing us to have specific distances between QDs and AuNRs and well-defined polarization states.

4. Conclusion

In conclusion, in this report we show that the QD-AuNR hybrid system can support molecular-like collective resonances. The existence of such resonances is due to quantum coherence in QD which can be controlled by geometrical and environmental variation in the system. We study how the variation of center-to-center distance and the environmental dielectric constant causes dramatic spectral changes in the energy transfer rate between the particles and optical properties such as red and blue shift in exciton energy, dispersion, absorption and total electric field experienced by QD). These are very interesting results and can be useful for developing nanoscale plasmonic devices, particularly for chemical and biological sensing applications.

References and links

1.

M. Toishi, D. Englund, A. Faraon, and J. Vucković, “High-brightness single photon source from a quantum dot in a directional-emission nanocavity,” Opt. Express 17(17), 14618–14626 (2009). [CrossRef] [PubMed]

2.

I. Fushman, D. Englund, A. Faraon, N. Stoltz, P. Petroff, and J. Vučković, “Controlled phase shifts with a single quantum dot,” Science 320(5877), 769–772 (2008). [CrossRef] [PubMed]

3.

V. Wood and V. Bulović, “Colloidal quantum dot light-emitting devices,” Nano Rev 1(0), 5202 (2010). [CrossRef] [PubMed]

4.

J. Chandrasekaran, D. Nithyaprakash, K. B. Ajjan, S. Maruthamuthu, D. Manoharan, and S. Kumar, “Hybrid solar cell based on blending of organic and inorganic materials—An overview,” Renew. Sustain. Energy Rev. 15(2), 1228–1238 (2011). [CrossRef]

5.

S. J. Rosenthal, J. C. Chang, O. Kovtun, J. R. McBride, and I. D. Tomlinson, “Biocompatible quantum dots for biological applications,” Chem. Biol. 18(1), 10–24 (2011). [CrossRef] [PubMed]

6.

S. Pang, R. E. Beckham, and K. E. Meissner, “Quantum dot-embedded microspheres for remote refractive index sensing,” Appl. Phys. Lett. 92(22), 221108 (2008). [CrossRef] [PubMed]

7.

T. Nakamura, T. Asano, K. Kojima, T. Kojima, and S. Noda, “Controlling the emission of quantum dots embedded in photonic crystal nanocavity by manipulating Q-factor and detuning,” Phys. Rev. B 84(24), 245309 (2011). [CrossRef]

8.

K. Hennessy, A. Badolato, M. Winger, D. Gerace, M. Atatüre, S. Gulde, S. Fält, E. L. Hu, and A. Imamoğlu, “Quantum nature of a strongly coupled single quantum dot-cavity system,” Nature 445(7130), 896–899 (2007). [CrossRef] [PubMed]

9.

M. Achermann, “Exciton-plasmon interactions in metal-semiconductor nanostructures,” J. Phys. Chem. Lett. 1(19), 2837–2843 (2010). [CrossRef]

10.

R. F. Oulton, V. J. Sorger, T. Zentgraf, R.-M. Ma, C. Gladden, L. Dai, G. Bartal, and X. Zhang, “Plasmon lasers at deep subwavelength scale,” Nature 461(7264), 629–632 (2009). [CrossRef] [PubMed]

11.

J. Lee, P. Hernandez, J. Lee, A. O. Govorov, and N. A. Kotov, “Exciton-plasmon interactions in molecular spring assemblies of nanowires and wavelength-based protein detection,” Nat. Mater. 6(4), 291–295 (2007). [CrossRef] [PubMed]

12.

S. M. Sadeghi, “Plasmonic metaresonances: Molecular resonances in quantum dot-metallic nanoparticle conjugates,” Phys. Rev. B 79(23), 233309 (2009). [CrossRef]

13.

A. Hatef, S. M. Sadeghi, and M. R. Singh, “Coherent molecular resonances in quantum dot-metallic nanoparticle systems: coherent self-renormalization and structural effects,” Nanotechnology 23(20), 205203 (2012). [CrossRef] [PubMed]

14.

S. M. Sadeghi, “Plasmonic metaresonance nanosensors: Ultrasensitive tunable optical sensors based on nanoparticle molecules,” IEEE Trans. Nanobioscience 10, 566–571 (2011).

15.

K.-S. Lee and M. A. El-Sayed, “Dependence of the enhanced optical scattering efficiency relative to that of absorption for gold metal nanorods on aspect ratio, size, end-cap shape, and medium refractive index,” J. Phys. Chem. B 109(43), 20331–20338 (2005). [CrossRef] [PubMed]

16.

H. C. Van de Hulst, Light Scattering by Small Particles (John Wiley & Sons, Inc., 1951).

17.

P. Michler, ed., Single Semiconductor Quantum Dots (Springer, 2009).

18.

O. Marlan, Scully and M. S. Zubairy, Quantum Optics (Cambridge, 1997).

19.

J.-Y. Yan, W. Zhang, S. Duan, X.-G. Zhao, and A. O. Govorov, “Optical properties of coupled metal-semiconductor and metal-molecule nanocrystal complexes: Role of multipole effects,” Phys. Rev. B 77(16), 165301 (2008). [CrossRef]

20.

P. B. Johnson and R. W. Christy, “Optical constants of the noble metals,” Phys. Rev. B 6(12), 4370–4379 (1972). [CrossRef]

21.

A. Trügler and U. Hohenester, “Strong coupling between a metallic nanoparticle and a single molecule,” Phys. Rev. B 77(11), 115403 (2008). [CrossRef]

22.

J. A. Scholl, A. L. Koh, and J. A. Dionne, “Quantum plasmon resonances of individual metallic nanoparticles,” Nature 483(7390), 421–427 (2012). [CrossRef] [PubMed]

23.

Z. Deng, O. Schulz, S. Lin, B. Ding, X. Liu, X. Wei, R. Ros, H. Yan, and Y. Liu, “Aqueous synthesis of zinc blende CdTe/CdS magic-core/thick-shell tetrahedral-shaped nanocrystals with emission tunable to near-infrared,” J. Am. Chem. Soc. 132(16), 5592–5593 (2010). [CrossRef] [PubMed]

24.

R. D. Artuso, G. W. Bryant, A. Garcia-Etxarri, and J. Aizpurua, “Using local fields to tailor hybrid quantum-dot/metal nanoparticle systems,” Phys. Rev. B 83(23), 235406 (2011). [CrossRef]

25.

P. Guyot-Sionnest, X. Peng, and D. Mingos, Intraband Spectroscopy and Semiconductor Nanocrystals Semiconductor Nanocrystals and Silicate Nanoparticles (Springer Berlin / Heidelberg, 2005), pp. 59–77.

26.

P. Anger, P. Bharadwaj, and L. Novotny, “Enhancement and Quenching of Single-Molecule Fluorescence,” Phys. Rev. Lett. 96(11), 113002 (2006). [CrossRef] [PubMed]

27.

J.-Y. Yan, W. Zhang, S. Duan, X.-G. Zhao, and A. O. Govorov, “Optical properties of coupled metal-semiconductor and metal-molecule nanocrystal complexes: Role of multipole effects,” Phys. Rev. B 77(16), 165301 (2008). [CrossRef]

28.

R. D. Artuso and G. W. Bryant, “Optical response of strongly coupled quantum dot-metal nanoparticle systems: Double peaked Fano structure and bistability,” Nano Lett. 8(7), 2106–2111 (2008). [CrossRef] [PubMed]

29.

H. Hartmut and W. K. Stephan, Quantum Theory of The Optical And Electronic Properties Of Semiconductors (World Scientific, 2004).

30.

T. Pons, I. L. Medintz, K. E. Sapsford, S. Higashiya, A. F. Grimes, D. S. English, and H. Mattoussi, “On the quenching of semiconductor quantum dot photoluminescence by proximal gold nanoparticles,” Nano Lett. 7(10), 3157–3164 (2007). [CrossRef] [PubMed]

31.

I. L. Medintz, K. E. Sapsford, A. R. Clapp, T. Pons, S. Higashiya, J. T. Welch, and H. Mattoussi, “Designer variable repeat length polypeptides as scaffolds for surface immobilization of quantum dots,” J. Phys. Chem. B 110(22), 10683–10690 (2006). [CrossRef] [PubMed]

32.

J. M. Slocik, F. Tam, N. J. Halas, and R. R. Naik, “Peptide-assembled optically responsive nanoparticle complexes,” Nano Lett. 7(4), 1054–1058 (2007). [CrossRef] [PubMed]

33.

R. Kadono, W. Higemoto, K. Nagamine, and F. L. Pratt, “An atom in the bloch state,” Phys. Rev. Lett. 83(5), 987–990 (1999). [CrossRef]

OCIS Codes
(270.1670) Quantum optics : Coherent optical effects
(280.4788) Remote sensing and sensors : Optical sensing and sensors

ToC Category:
Quantum Optics

History
Original Manuscript: September 21, 2012
Revised Manuscript: November 8, 2012
Manuscript Accepted: January 7, 2013
Published: March 1, 2013

Citation
Ali Hatef, Seyed M. Sadeghi, Simon Fortin-Deschênes, Etienne Boulais, and Michel Meunier, "Coherently-enabled environmental control of optics and energy transfer pathways of hybrid quantum dot-metallic nanoparticle systems," Opt. Express 21, 5643-5653 (2013)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-21-5-5643


Sort:  Author  |  Year  |  Journal  |  Reset  

References

  1. M. Toishi, D. Englund, A. Faraon, and J. Vucković, “High-brightness single photon source from a quantum dot in a directional-emission nanocavity,” Opt. Express17(17), 14618–14626 (2009). [CrossRef] [PubMed]
  2. I. Fushman, D. Englund, A. Faraon, N. Stoltz, P. Petroff, and J. Vučković, “Controlled phase shifts with a single quantum dot,” Science320(5877), 769–772 (2008). [CrossRef] [PubMed]
  3. V. Wood and V. Bulović, “Colloidal quantum dot light-emitting devices,” Nano Rev1(0), 5202 (2010). [CrossRef] [PubMed]
  4. J. Chandrasekaran, D. Nithyaprakash, K. B. Ajjan, S. Maruthamuthu, D. Manoharan, and S. Kumar, “Hybrid solar cell based on blending of organic and inorganic materials—An overview,” Renew. Sustain. Energy Rev.15(2), 1228–1238 (2011). [CrossRef]
  5. S. J. Rosenthal, J. C. Chang, O. Kovtun, J. R. McBride, and I. D. Tomlinson, “Biocompatible quantum dots for biological applications,” Chem. Biol.18(1), 10–24 (2011). [CrossRef] [PubMed]
  6. S. Pang, R. E. Beckham, and K. E. Meissner, “Quantum dot-embedded microspheres for remote refractive index sensing,” Appl. Phys. Lett.92(22), 221108 (2008). [CrossRef] [PubMed]
  7. T. Nakamura, T. Asano, K. Kojima, T. Kojima, and S. Noda, “Controlling the emission of quantum dots embedded in photonic crystal nanocavity by manipulating Q-factor and detuning,” Phys. Rev. B84(24), 245309 (2011). [CrossRef]
  8. K. Hennessy, A. Badolato, M. Winger, D. Gerace, M. Atatüre, S. Gulde, S. Fält, E. L. Hu, and A. Imamoğlu, “Quantum nature of a strongly coupled single quantum dot-cavity system,” Nature445(7130), 896–899 (2007). [CrossRef] [PubMed]
  9. M. Achermann, “Exciton-plasmon interactions in metal-semiconductor nanostructures,” J. Phys. Chem. Lett.1(19), 2837–2843 (2010). [CrossRef]
  10. R. F. Oulton, V. J. Sorger, T. Zentgraf, R.-M. Ma, C. Gladden, L. Dai, G. Bartal, and X. Zhang, “Plasmon lasers at deep subwavelength scale,” Nature461(7264), 629–632 (2009). [CrossRef] [PubMed]
  11. J. Lee, P. Hernandez, J. Lee, A. O. Govorov, and N. A. Kotov, “Exciton-plasmon interactions in molecular spring assemblies of nanowires and wavelength-based protein detection,” Nat. Mater.6(4), 291–295 (2007). [CrossRef] [PubMed]
  12. S. M. Sadeghi, “Plasmonic metaresonances: Molecular resonances in quantum dot-metallic nanoparticle conjugates,” Phys. Rev. B79(23), 233309 (2009). [CrossRef]
  13. A. Hatef, S. M. Sadeghi, and M. R. Singh, “Coherent molecular resonances in quantum dot-metallic nanoparticle systems: coherent self-renormalization and structural effects,” Nanotechnology23(20), 205203 (2012). [CrossRef] [PubMed]
  14. S. M. Sadeghi, “Plasmonic metaresonance nanosensors: Ultrasensitive tunable optical sensors based on nanoparticle molecules,” IEEE Trans. Nanobioscience10, 566–571 (2011).
  15. K.-S. Lee and M. A. El-Sayed, “Dependence of the enhanced optical scattering efficiency relative to that of absorption for gold metal nanorods on aspect ratio, size, end-cap shape, and medium refractive index,” J. Phys. Chem. B109(43), 20331–20338 (2005). [CrossRef] [PubMed]
  16. H. C. Van de Hulst, Light Scattering by Small Particles (John Wiley & Sons, Inc., 1951).
  17. P. Michler, ed., Single Semiconductor Quantum Dots (Springer, 2009).
  18. O. Marlan, Scully and M. S. Zubairy, Quantum Optics (Cambridge, 1997).
  19. J.-Y. Yan, W. Zhang, S. Duan, X.-G. Zhao, and A. O. Govorov, “Optical properties of coupled metal-semiconductor and metal-molecule nanocrystal complexes: Role of multipole effects,” Phys. Rev. B77(16), 165301 (2008). [CrossRef]
  20. P. B. Johnson and R. W. Christy, “Optical constants of the noble metals,” Phys. Rev. B6(12), 4370–4379 (1972). [CrossRef]
  21. A. Trügler and U. Hohenester, “Strong coupling between a metallic nanoparticle and a single molecule,” Phys. Rev. B77(11), 115403 (2008). [CrossRef]
  22. J. A. Scholl, A. L. Koh, and J. A. Dionne, “Quantum plasmon resonances of individual metallic nanoparticles,” Nature483(7390), 421–427 (2012). [CrossRef] [PubMed]
  23. Z. Deng, O. Schulz, S. Lin, B. Ding, X. Liu, X. Wei, R. Ros, H. Yan, and Y. Liu, “Aqueous synthesis of zinc blende CdTe/CdS magic-core/thick-shell tetrahedral-shaped nanocrystals with emission tunable to near-infrared,” J. Am. Chem. Soc.132(16), 5592–5593 (2010). [CrossRef] [PubMed]
  24. R. D. Artuso, G. W. Bryant, A. Garcia-Etxarri, and J. Aizpurua, “Using local fields to tailor hybrid quantum-dot/metal nanoparticle systems,” Phys. Rev. B83(23), 235406 (2011). [CrossRef]
  25. P. Guyot-Sionnest, X. Peng, and D. Mingos, Intraband Spectroscopy and Semiconductor Nanocrystals Semiconductor Nanocrystals and Silicate Nanoparticles (Springer Berlin / Heidelberg, 2005), pp. 59–77.
  26. P. Anger, P. Bharadwaj, and L. Novotny, “Enhancement and Quenching of Single-Molecule Fluorescence,” Phys. Rev. Lett.96(11), 113002 (2006). [CrossRef] [PubMed]
  27. J.-Y. Yan, W. Zhang, S. Duan, X.-G. Zhao, and A. O. Govorov, “Optical properties of coupled metal-semiconductor and metal-molecule nanocrystal complexes: Role of multipole effects,” Phys. Rev. B77(16), 165301 (2008). [CrossRef]
  28. R. D. Artuso and G. W. Bryant, “Optical response of strongly coupled quantum dot-metal nanoparticle systems: Double peaked Fano structure and bistability,” Nano Lett.8(7), 2106–2111 (2008). [CrossRef] [PubMed]
  29. H. Hartmut and W. K. Stephan, Quantum Theory of The Optical And Electronic Properties Of Semiconductors (World Scientific, 2004).
  30. T. Pons, I. L. Medintz, K. E. Sapsford, S. Higashiya, A. F. Grimes, D. S. English, and H. Mattoussi, “On the quenching of semiconductor quantum dot photoluminescence by proximal gold nanoparticles,” Nano Lett.7(10), 3157–3164 (2007). [CrossRef] [PubMed]
  31. I. L. Medintz, K. E. Sapsford, A. R. Clapp, T. Pons, S. Higashiya, J. T. Welch, and H. Mattoussi, “Designer variable repeat length polypeptides as scaffolds for surface immobilization of quantum dots,” J. Phys. Chem. B110(22), 10683–10690 (2006). [CrossRef] [PubMed]
  32. J. M. Slocik, F. Tam, N. J. Halas, and R. R. Naik, “Peptide-assembled optically responsive nanoparticle complexes,” Nano Lett.7(4), 1054–1058 (2007). [CrossRef] [PubMed]
  33. R. Kadono, W. Higemoto, K. Nagamine, and F. L. Pratt, “An atom in the bloch state,” Phys. Rev. Lett.83(5), 987–990 (1999). [CrossRef]

Cited By

Alert me when this paper is cited

OSA is able to provide readers links to articles that cite this paper by participating in CrossRef's Cited-By Linking service. CrossRef includes content from more than 3000 publishers and societies. In addition to listing OSA journal articles that cite this paper, citing articles from other participating publishers will also be listed.


« Previous Article  |  Next Article »

OSA is a member of CrossRef.

CrossCheck Deposited