149 research outputs found
The Mollow triplets under few-photon excitation
Resonant excitation is an essential tool in the development of semiconductor
quantum dots (QDs) for quantum information processing. One central challenge is
to enable a transparent access to the QD signal without post-selection
information loss. A viable path is through cavity enhancement, which has
successfully lifted the resonantly scattered field strength over the laser
background under \emph{weak} excitation. Here, we extend this success to the
\emph{saturation} regime using a QD-micropillar device with a Purcell factor of
10.9 and an ultra-low background cavity reflectivity of just 0.0089. We achieve
a signal to background ratio of 50 and an overall system responsivity of 3~\%,
i.e., we detect on average 0.03 resonantly scattered single photons for every
incident laser photon. Raising the excitation to the few-photon level, the QD
response is brought into saturation where we observe the Mollow triplets as
well as the associated cascade single photon emissions, without resort to any
laser background rejection technique. Our work offers a new perspective toward
QD cavity interface that is not restricted by the laser background.Comment: 8 Figures and 9 Pages. Comments are welcom
Dynamic resonance fluorescence in solid-state cavity quantum electrodynamics
The coherent interaction between a two-level system and electromagnetic
fields serves as a foundation for fundamental quantum physics and modern
photonic quantum technology. A profound example is resonance fluorescence,
where the non-classical photon emission appears in the form of a Mollow-triplet
when a two-level system is continuously driven by a resonant laser. Pushing
resonance fluorescence from a static to dynamic regime by using short optical
pulses generates on-demand emissions of highly coherent single photons. Further
increasing the driving strength in the dynamical regime enables the pursuit of
exotic non-classical light emission in photon number superposition, photon
number entanglement, and photon bundle states. However, the long-sought-after
spectrum beyond the Mollow-triplet, a characteristic of dynamic resonance
fluorescence under strong driving strength, has not been observed yet. Here we
report the direct observation and systematic investigations of dynamic
resonance fluorescence spectra beyond the Mollow-triplet in a solid-state
cavity quantum electrodynamic system. The dynamic resonance fluorescence
spectra with up to five pairs of side peaks, excitation detuning induced
spectral asymmetry, and cavity filtering effect are observed and quantitatively
modeled by a full quantum model with phonon scattering included. Time-resolved
measurements further reveal that the multiple side peaks originate from
interference of the emission associated with different temporal positions of
the excitation pulses. Our work facilitates the generation of a variety of
exotic quantum states of light with dynamic driving of two-level systems.Comment: Manuscript submitted on 19th May 202
Design of 2 μm Wavelength Polarization Mode Controllers
A single-slot waveguide for transverse electric (TE) to transverse magnetic (TM) mode conversion operating at wavelengths around 2 μm is proposed based on an InGaSb/AlGaAsSb quantum well structure. The polarization mode convertor has a deep-etched ridge waveguide and a single shallow-etched slot, and can be fabricated in a single stage of dry-etching. The dependence of polarization conversion efficiency on slot width, slot position, slot depth and waveguide length was investigated, and a design that was insensitive to fabrication tolerances was identified. A TE-TM mode conversion efficiency of more than 97% can be obtained in a 2141-μm-long waveguide
Zinc-blende and wurtzite GaAs quantum dots in nanowires studied using hydrostatic pressure
We report both zinc-blende (ZB) and wurtzite (WZ) crystal phase
self-assembled GaAs quantum dots (QDs) embedding in a single GaAs/AlGaAs
core-shell nanowires (NWs). Optical transitions and single-photon
characteristics of both kinds of QDs have been investigated by measuring
photoluminescence (PL) and time-resolved PL spectra upon application of
hydrostatic pressure. We find that the ZB QDs are of direct band gap transition
with short recombination lifetime (~1 ns) and higher pressure coefficient
(75-100 meV/GPa). On the contrary, the WZ QDs undergo a direct-to-pseudodirect
bandgap transition as a result of quantum confinement effect, with remarkably
longer exciton lifetime (4.5-74.5 ns) and smaller pressure coefficient (28-53
meV/GPa). These fundamentally physical properties are further examined by
performing state-of-the-art atomistic pseudopotential calculations
Scalable deterministic integration of two quantum dots into an on-chip quantum circuit
Integrated quantum photonic circuits (IQPCs) with deterministically
integrated quantum emitters are critical elements for scalable quantum
information applications and have attracted significant attention in recent
years. However, scaling up them towards fully functional photonic circuits with
multiple deterministically integrated quantum emitters to generate photonic
input states remains a great challenge. In this work, we report on a monolithic
prototype IQPC consisting of two pre-selected quantum dots deterministically
integrated into nanobeam cavities at the input ports of a 2x2 multimode
interference beam-splitter. The on-chip beam splitter exhibits a splitting
ratio of nearly 50/50 and the integrated quantum emitters have high
single-photon purity, enabling on-chip HBT experiments, depicting deterministic
scalability. Overall, this marks a cornerstone toward scalable and
fully-functional IQPCs
Assessing the alignment accuracy of state-of-the-art deterministic fabrication methods for single quantum dot devices
The realization of efficient quantum light sources relies on the integration
of self-assembled quantum dots (QDs) into photonic nanostructures with high
spatial positioning accuracy. In this work, we present a comprehensive
investigation of the QD position accuracy, obtained using two marker-based QD
positioning techniques, photoluminescence (PL) and cathodoluminescence (CL)
imaging, as well as using a marker-free in-situ electron beam lithography
(in-situ EBL) technique. We employ four PL imaging configurations with three
different image processing approaches and compare them with CL imaging. We
fabricate circular mesa structures based on the obtained QD coordinates from
both PL and CL image processing to evaluate the final positioning accuracy.
This yields final position offset of the QD relative to the mesa center of
= (-4058) nm and = (-3985) nm with PL imaging and
= (-3930) nm and = (2577) nm with CL imaging, which
are comparable to the offset = (2040) nm and =
(-1439) nm obtained using the in-situ EBL method. We discuss the possible
causes of the observed offsets, which are significantly larger than the QD
localization uncertainty obtained from simply imaging the QD light emission
from an unstructured wafer. Our study highlights the influences of the image
processing technique and the subsequent fabrication process on the final
positioning accuracy for a QD placed inside a photonic nanostructure
Asymmetric Chiral Coupling in a Topological Resonator
Chiral light-matter interactions supported by topological edge modes at the
interface of valley photonic crystals provide a robust method to implement the
unidirectional spin transfer. The valley topological photonic crystals possess
a pair of counterpropagating edge modes. The edge modes are robust against the
sharp bend of and , which can form a resonator with
whispering gallery modes. Here, we demonstrate the asymmetric emission of
chiral coupling from single quantum dots in a topological resonator by tuning
the coupling between a quantum emitter and a resonator mode. Under a magnetic
field in Faraday configuration, the exciton state from a single quantum dot
splits into two exciton spin states with opposite circularly polarized
emissions due to Zeeman effect. Two branches of the quantum dot emissions
couple to a resonator mode in different degrees, resulting in an asymmetric
chiral emission. Without the demanding of site-control of quantum emitters for
chiral quantum optics, an extra degree of freedom to tune the chiral contrast
with a topological resonator could be useful for the development of on-chip
integrated photonic circuits.Comment: 13 pages, 4 figure
Controllable Spin-Resolved Photon Emission Enhanced by Slow-Light Mode in Photonic Crystal Waveguides on Chip
We report the slow-light enhanced spin-resolved in-plane emission from a
single quantum dot (QD) in a photonic crystal waveguide (PCW). The slow light
dispersions in PCWs are designed to match the emission wavelengths of single
QDs. The resonance between two spin states emitted from a single QD and a slow
light mode of a waveguide is investigated under a magnetic field with Faraday
configuration. Two spin states of a single QD experience different degrees of
enhancement as their emission wavelengths are shifted by combining diamagnetic
and Zeeman effects with an optical excitation power control. A circular
polarization degree up to 0.81 is achieved by changing the off-resonant
excitation power. Strongly polarized photon emission enhanced by a slow light
mode shows great potential to attain controllable spin-resolved photon sources
for integrated optical quantum networks on chip.Comment: 7 pages,5 figure
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