[show abstract][hide abstract] ABSTRACT: We propose a method to overcome Auger recombination in nanocrystal quantum
dot lasers using cavity-enhanced spontaneous emission. We derive a numerical
model for a laser composed of nanocrystal quantum dots coupled to optical
nanocavities with small mode-volume. Using this model, we demonstrate that
spontaneous emission enhancement of the biexciton transition lowers the lasing
threshold by reducing the effect of Auger recombination. We analyze a photonic
crystal nanobeam cavity laser as a realistic device structure that implements
the proposed approach.
[show abstract][hide abstract] ABSTRACT: We demonstrate spontaneous emission rate enhancement and saturable absorption of cadmium selenide colloidal quantum dots coupled to a nanobeam photonic crystal cavity. We perform time-resolved lifetime measurements and observe an average enhancement of 4.6 for the spontaneous emission rate of quantum dots located at the cavity as compared to those located on an unpatterned surface. We also demonstrate that the cavity linewidth narrows with increasing pump intensity due to quantum dot saturable absorption.
[show abstract][hide abstract] ABSTRACT: We experimentally demonstrate that the Mollow triplet sidebands of a quantum
dot strongly coupled to a cavity exhibit anomalous power induced broadening and
enhanced emission when one sideband is tuned over the cavity frequency. We
observe a nonlinear increase of the sideband linewidth with excitation power
when the Rabi frequency exceeds the detuning between the quantum dot and the
cavity, consistent with a recent theoretical model that accounts for acoustic
phonon-induced processes between the exciton and the cavity. In addition, the
sideband tuned to the cavity shows strong resonant emission enhancement.
[show abstract][hide abstract] ABSTRACT: Synthetic nanostructures, such as nanoparticles and nanowires, can serve as modular building blocks for integrated nanoscale systems. We demonstrate a microfluidic approach for positioning, orienting, and assembling such nanostructures into nanoassemblies. We use flow control combined with a crosslinking photoresist to position and immobilize nanostructures in desired positions and orientations. Immobilized nanostructures can serve as pivots, barriers, and guides for precise placement of subsequent nanostructures.
[show abstract][hide abstract] ABSTRACT: We demonstrate reversible strain-tuning of a quantum dot strongly coupled to
a photonic crystal cavity. We observe an average redshift of 0.45 nm for
quantum dots located inside the cavity membrane, achieved with an electric
field of 15 kV/cm applied to a piezo-electric actuator. Using this technique,
we demonstrate the ability to tune a quantum dot into resonance with a photonic
crystal cavity in the strong coupling regime, resulting in a clear
anti-crossing. The bare cavity resonance is less sensitive to strain than the
quantum dot and shifts by only 0.078 nm at the maximum applied electric field.
[show abstract][hide abstract] ABSTRACT: Integrated nanophotonic devices create strong light-matter interactions
that are important for the development of solid-state quantum networks,
distributed quantum computers and ultralow-power optoelectronics. A key
component for many of these applications is the photonic quantum logic
gate, where the quantum state of a solid-state quantum bit (qubit)
conditionally controls the state of a photonic qubit. These gates are
crucial for the development of robust quantum networks, non-destructive
quantum measurements and strong photon-photon interactions. Here, we
experimentally realize a quantum logic gate between an optical photon
and a solid-state qubit. The qubit is composed of a quantum dot strongly
coupled to a nanocavity, which acts as a coherently controllable qubit
system that conditionally flips the polarization of a photon on
picosecond timescales, implementing a controlled-NOT gate. Our results
represent an important step towards solid-state quantum networks and
provide a versatile approach for probing quantum dot-photon interactions
on ultrafast timescales.
[show abstract][hide abstract] ABSTRACT: We present a method to control the resonant coupling interaction in a coupled-cavity photonic crystal molecule by using a local and reversible photochromic tuning technique. We demonstrate the ability to tune both a two-cavity and a three-cavity photonic crystal molecule through the resonance condition by selectively tuning the individual cavities. Using this technique, we can quantitatively determine important parameters of the coupled-cavity system such as the photon tunneling rate. This method can be scaled to photonic crystal molecules with larger numbers of cavities, which provides a versatile method for studying strong interactions in coupled resonator arrays.
[show abstract][hide abstract] ABSTRACT: Single semiconductor quantum-dots (QDs) strongly coupled to photonic
crystal cavities are a strong candidate for single photon generation,
ultra-fast all optical switching and quantum information processing.
Recent experiments on coupled-cavity quantum dot systems show possible
manipulation of emission wavelength of the dot through optical Stark
effect. Interesting dynamical features arise when the Stark pulse
duration is comparable to QD-cavity interaction time. Here, we present a
theoretical treatment of these dynamical effects and investigate
dynamical emission spectrum, energy transfer and single photon
generation. We study these effects through numerical solution of the
full master equation. We demonstrate that dynamic Stark effects can be
used to generate ultra-fast indistinguishable single photons using rapid
Stark tuning of the quantum dot. The theoretical limit for the speed is
shown to be faster than adiabatic rapid passage technique used for
microwave photon generation in circuit QED. A systematic study of role
of device parameters such as pulse-shape, dot-cavity coupling and
incoherent losses on the efficiency and speed of single photon
generation is also presented for possible experimental realization.
[show abstract][hide abstract] ABSTRACT: Understanding and controlling the interactions between single quantum
emitters and plasmonic nanostructures is important for a wide variety of
applications in quantum optics and nanophotonics. Metal nanostructures
provide subwavelength confinement of electromagnetic fields in the form
of surface plasmon polaritons, which can enhance optical nonlinearities
for improved light-matter interactions. In this talk we will present
recent results on nano-manipulation of single colloidal quantum dots
(QDs) for deterministic probing of light-matter interactions in
plasmonic nanostructures. Single QDs are manipulated using a combination
of microfluidics and engineered fluid chemistry. We achieve
deterministic positioning with 50 nm accuracy and demonstrate probing of
the surface plasmon mode of a silver nanowire. Spatially variant
interactions are quantified by measuring the coupling rate of the QD
into the wire mode as well as changes to the QD emission lifetime. The
resulting interactions are resolved with nanoscale resolution and reveal
features such as the evanescent field decay away from the wire surface
and interference along the wire length.
[show abstract][hide abstract] ABSTRACT: Strong interactions between matter quantum bits (qubits) and photons
play an essential role in quantum information. Quantum dots (QDs)
provide a promising implementation of a matter qubit that can be
strongly coupled to optical nanocavities, providing a direct
light-matter interface. We use this light-matter interface to
demonstrate a picosecond timescale controlled NOT logic gate between a
QD and a photon, which is a fundamental building block for complex
quantum logic. Coherent control of the QD qubit state by optical pulses
results in a modification of cavity reflectivity, enabling a conditional
bit-flip on the polarization state of a photon incident on the cavity.
[show abstract][hide abstract] ABSTRACT: Single QDs are desirable probe objects for studying near-field optical
interactions with photonic structures, however, they are often very
difficult to manipulate due to their small sizes. Here, we describe a
technique for the manipulation of individual colloidal CdSe/ZnS quantum
dots (QDs) with nanometer accuracy along a two dimensional surface. A
microfluidic approach is described which provides two-dimensional
positioning of single QDs with nanoscale accuracy. In addition, we
discuss the engineering of a water-based fluid that provides
localization of QDs to within 100 nm of the channel surface. Through a
combination of surface localization and in plane manipulation, a setup
is described where single QDs can be utilized as single emitter probes
for studying local light-matter interactions in a planar geometry.
[show abstract][hide abstract] ABSTRACT: Strongly coupled photonic crystal (PhC) resonator systems provide a
promising platform for studying cavity quantum electrodynamics (QED)
using semiconductor quantum dots (QDs). These device structures enable
important applications such as photon blockade, quantum simulation,
quantum-optical Josephson interferometer, and quantum phase transition
of light. Many of these applications require the ability to accurately
tune the resonant frequencies of individual cavities in the array, which
provides a method to control their coupling interactions. This tuning
method must be sufficiently local to address individual cavities spaced
by less than 1 micron spatial separation. Here, we present a method for
controlling the coupling interaction of photonic crystal cavity arrays
by using a local and reversible photochromic tuning technique. By
locally altering the refractive index of the photochromic material
all-optically, the coupling interaction between two cavity modes could
be modified over a tuning range as large as 700 GHz. By using this
technique, we demonstrate the ability to couple photonic crystal
cavities with a normal mode splitting of only 31.50 GHz. We further
demonstrate that this tuning method can be extended to control the
coupling interaction in larger cavity arrays.
[show abstract][hide abstract] ABSTRACT: The interaction of semiconductor quantum dots (QD) with photonic crystal
resonator systems provides a highly integrated, solid-state platform for
studies in ultra-low energy nonlinear optics and quantum optical
phenomena. Here, we present a method to tune a semiconductor quantum dot
(QD) all-optically into resonance with a cavity mode using the
non-resonant optical Stark effect. We use a system comprised of two
evanescently coupled photonic crystal cavities containing a single QD in
one of the cavities. One mode of the coupled cavity system is used to
generate a cavity-enhanced optical Stark shift, enabling the QD to be
resonantly tuned to the other cavity mode. We show that the optical
tuning of the QD results in a large radiative enhancement of the QD
photon emission via the Purcell effect. We will further discuss dynamic
experiments in the system using a Stark laser that has a time-duration
on the order of the system decay rates. We will show that under this
scenario, the cavity-QD spectrum provides a rich array of information on
the system dynamics. The experiments are promising for a variety of
applications in highly-efficient single photon generation, cavity
quantum electrodynamics, ultra-fast optical switching, and classical and
quantum information processing.
[show abstract][hide abstract] ABSTRACT: Plasmonic nanostructures confine light on the nanoscale, enabling ultra-compact optical devices that exhibit strong light-matter interactions. Quantum dots are ideal for probing plasmonic devices because of their nanoscopic size and desirable emission properties. However, probing with single quantum dots has remained challenging because their small size also makes them difficult to manipulate. Here we demonstrate the use of quantum dots as on-demand probes for imaging plasmonic nanostructures, as well as for realizing spontaneous emission control at the single emitter level with nanoscale spatial accuracy. A single quantum dot is positioned with microfluidic flow control to probe the local density of optical states of a silver nanowire, achieving 12 nm imaging accuracy. The high spatial accuracy of this scanning technique enables a new method for spontaneous emission control where interference of counter-propagating surface plasmon polaritons results in spatial oscillations of the quantum dot lifetime as it is positioned along the wire axis.
[show abstract][hide abstract] ABSTRACT: We describe and employ a recently developed polaron master equation model to study the fluorescence spectra of a coherently driven quantum dot (QD) placed within a high-Q semiconductor microcavity (with Q the quality factor). We investigate phonon-induced damping in a regime where many cavity photons are required, and we also compare the resonance fluorescence spectra obtained using an effective phonon master equation in Lindblad form where simple analytical expressions are identified for various phonon-induced scattering rates. We consider two separate continuous-wave pumping scenarios, where either the system is driven through exciton pumping or the system is driven via the cavity. The cavity-QED (quantum electrodynamics) system is pumped sufficiently strongly such that the low-energy sideband of the Mollow triplet is tuned across the cavity mode resonance which is negatively detuned from the QD. For comparison, we also consider the case where the QD-cavity detuning is large enough such that the Mollow triplets do not spectrally overlap with the cavity mode. We find that the full width at half maximum (FWHM) of the high-energy Mollow sideband shows a pronounced nonlinear dependence on the pump intensity when the low-energy component of the triplet overlaps with the cavity mode (or vice versa), and can even be reduced with increased pumping. However, the FWHM depends linearly on the pump intensity when the Mollow triplets are far from the cavity resonance. We observe similar fluorescence spectra for both the exciton-driven system and the cavity-driven system.
Photonics and Nanostructures - Fundamentals and Applications 10/2012; 10(4):359–368. · 1.79 Impact Factor
[show abstract][hide abstract] ABSTRACT: We demonstrate a method for tuning a semiconductor quantum dot (QD) onto resonance with a cavity mode all-optically using a system comprised of two evanescently coupled cavities containing a single QD. One resonance of the coupled cavity system is utilized to generate a cavity enhanced optical Stark shift, enabling the QD to be resonantly tuned to the other cavity mode. A twenty-seven fold increase in photon emission from the QD is measured when the off-resonant QD is Stark shifted onto the cavity mode resonance, which is attributed to radiative enhancement of the QD. A maximum tuning of 0.06 nm is achieved for the QD at an incident power of 88 μW.
[show abstract][hide abstract] ABSTRACT: We demonstrate fast nonlinear optical switching between two laser pulses with as few as 140 photons of pulse energy by utilizing strong coupling between a single quantum dot (QD) and a photonic crystal cavity. The cavity-QD coupling is modified by a detuned pump pulse, resulting in a modulation of the scattered and transmitted amplitude of a time synchronized probe pulse that is resonant with the QD. The temporal switching response is measured to be as fast as 120 ps, demonstrating the ability to perform optical switching on picosecond timescales.
[show abstract][hide abstract] ABSTRACT: This article is on microscale flow control, on dynamically shaping flow fields in microfluidic devices to precisely manipulate cells, quantum dots (QDs), and nanowires (Figure 1). Compared to prior methods (Table 1), manipulating microscopic and nanoscopic objects by flow control can be achieved with simpler and easy-to-fabricate devices, can steer a wider variety of objects, and enables entirely new capabilities such as placement and immobilization of specific quantum dots to desired on-chip locations with nanoscale precision. A companion article  investigates flow control in the body and develops methods to shape magnetic fields to direct ferrofluids of therapeutic magnetic nanoparticles to disease locations in patients.
IEEE control systems 01/2012; 32(2):26-53. · 2.37 Impact Factor
[show abstract][hide abstract] ABSTRACT: Low power optical nonlinearities are a crucial requirement for data
routing and next generation all-optical processing. The majority of
nonlinear optical devices to date exploit weak nonlinearities from a
large ensemble of atomic systems, resulting in both high power
dissipation and a large device footprint. Quantum dots (QDs) coupled to
photonic crystals can provide significant reduction in both device size
and power dissipation. The interaction between these two systems creates
extremely strong light-matter interaction owing to the tight optical
confinement of photonic crystals and large oscillator strengths of QDs.
Such interactions enable optical nonlinearities near the single photon
level. In this work we investigate the nonlinear properties of QDs
coupled to photonic crystals. We demonstrate large optical Stark shift
with only 10 photons. We then propose and demonstrate a novel photonic
circuit that can route light on a chip with extremely low optical
[show abstract][hide abstract] ABSTRACT: We experimentally investigate the dynamic nonlinear response of a single
quantum dot (QD) strongly coupled to a photonic crystal cavity-waveguide
structure. The temporal response is measured by pump-probe excitation where a
control pulse propagating through the waveguide is used to create an optical
Stark shift on the QD, resulting in a large modification of the cavity
reflectivity. This optically induced cavity reflectivity modification switches
the propagation direction of a detuned signal pulse. Using this device we
demonstrate all-optical switching with only 14 attojoules of control pulse
energy. The response time of the switch is measured to be up to 8.4 GHz, which
is primarily limited by the cavity-QD interaction strength.