PHYSICAL REVIEW B 86, 155305 (2012)
Plasmonic effects in excitonic population transfer in a driven semiconductor–metal
nanoparticle hybrid system
M. A. Ant ´ on,
*
F. Carre˜ no, Sonia Melle, Oscar G. Calder´ on, and E. Cabrera-Granado
1
Escuela Universitaria de
´
Optica, Universidad Complutense de Madrid, C/ Arcos de Jal´ on 118, 28037 Madrid, Spain
Joel Cox and Mahi R. Singh
2
Department of Physics and Astronomy, The University of Western Ontario, London, Canada N6A 3K7
(Received 25 June 2012; published 5 October 2012)
We have investigated the coherent transfer of excitonic populations in a semiconductor quantum dot (SQD)
modulated by the surface plasmon of a metallic nanoparticle (MNP). The SQD is considered as a three-level
V-type atomic system. We applied a transform-limited laser pulse field resonant with the upper atomic levels
of the SQD. When the SQD is close enough to the MNP, the otherwise equally populated atomic levels can
be selectively excited. Selectivity population can be achieved by two physical mechanisms: an enhancement of
the Rabi frequencies that drive the optical transitions, which depends on the polarization arrangement, and a
frequency shift of the optical transitions that leads to a dynamical detuning.
DOI: 10.1103/PhysRevB.86.155305 PACS number(s): 78.67.−n
I. INTRODUCTION
Coherent optical control over individual quantum systems
in semiconductors has been the subject of active research
over the past decade
1
because of its potential applications
in atom optics,
2
preparation of entanglement,
3
and quantum
computation.
4,5
It also plays a central role in controlling
chemical reaction dynamics.
6
Three main strategies, that is,
temporal coherent control, optimal control, and adiabatic
passage, have been proposed to realize quantum coherent
control.
7
Stimulated Raman adiabatic passage (STIRAP)
1,8,9
has emerged as a very efficient and robust way to achieve com-
plete coherent population transfer between two discrete states
in an atomic or a molecular system. This technique has played
a major role in population transfer in and ladder systems.
1,10
There, complete population transfer from the initial state to the
target state without populating the intermediate state could be
achieved by applying time-delayed but partially overlapped
pump and Stokes pulses in a counterintuitive order while the
two-photon resonance and adiabatic conditions are fulfilled.
An alternative technique for population transfer is Raman
chirped adiabatic passage.
11–13
In this technique, chirped
lasers with time-dependent frequencies are used to sweep
through either one- or two-photon resonances in ladder and
systems, which results in efficient population transfer. Very
recently, robust quantum dot exciton generation via STIRAP
with frequency-swept optical pulses has been experimentally
reported.
14
It should be noted that selectivity cannot be realized
with a transform-limited pulse in the single-atom regime.
However, Netz et al. have shown that selectivity in a V-type
three-level system can be obtained by an applied field with
a large linear chirped rate and a proper direction of the
chirp.
15
Apart from one of the above-mentioned methods, it
has been shown that in dense atomic media, near dipole-dipole
interactions can cause a dynamic frequency chirp in the
system. In particular, Crenshaw and Bowden showed that a
dense two-level medium can be adiabatically inverted by the
so-called intrinsic self-chirping.
16
It is well known that dipole-dipole interactions occur natu-
rally in nanometer-scale hybrid heterostructures. Nanometer-
scale metallic structures have attracted plenty of attention
because they can dramatically modify the optical properties
of various optically active objects of similar dimensions, such
as atoms, molecules, or semiconductor quantum dots. The
interest in combining metal and semiconductor nanostructures
stems from their complementary optical properties. When
combined into heterostructures, the nanometer-scale vicinity
of the two material systems leads to interactions between
quantum-confined electronic states in semiconductor nanos-
tructures and dielectric-confined electromagnetic modes in the
metal counterpart. Such exciton-plasmon interactions allow
the tailoring of absorption and emission properties, control
of nanoscale energy-transfer processes, creation of new exci-
tations in the strong-coupling regime, and the enhancement
of optical nonlinearities.
17,18
Many interesting phenomena
have been found in these coupled nanocrystals, such as the
nonlinear Fano effect,
18
F¨ orster energy transfer,
19
and local
field enhancement.
20,21
In the presence of an external laser field, the surface
plasmon oscillation in metallic nanoparticles (MNPs) renor-
malizes the external field and enhances the electric field
in the semiconductor quantum dots (SQDs). The strong
modifications are conceptually well understood as a product
of free-electron oscillations in the metal that induce strong
localized electric fields near the surface of nanostructured
metals. The large fields and the high confinement associated
with the plasmonic resonances supported by these systems
enable strong interactions with other photonic elements such as
quantum emitters.
18,22,23
Significant attention has been focused
on the emerging field of quantum plasmonics with the goal
of making devices for quantum information processing
24,25
as single-photon transistors
26
or lasers.
27
Additionally, the
possibility of reaching the quantum regime using plasmonic
systems has also been addressed.
28–30
As a requisite for this
goal, a lot of effort has been devoted to achieve coherent
coupling between plasmons and a quantum emitter made of
a solid-state qubit such as, for instance, a quantum dot, a
single nitrogen vacancy center, or a single molecule, among
others. When SQDs are placed in close proximity to a MNP,
155305-1 1098-0121/2012/86(15)/155305(9) ©2012 American Physical Society