Search Results
Scanning single quantum emitter fluorescence lifetime imaging: Quantitative analysis of the local density of photonic states
Their intrinsic properties render single quantum systems as ideal tools for quantum enhanced sensing and microscopy. As an additional benefit, their size is typically on an atomic scale that enables sensing with very high spatial resolution. Here, we report on utilizing a single nitrogen vacancy center in nanodiamond for performing three-dimensional scanning-probe fluorescence lifetime imaging microscopy. By measuring changes of the single emitter's lifetime, information on the local density of optical states is acquired at the nanoscale. Three-dimensional ab initio discontinuous Galerkin time-domain simulations are used in order to verify the results and to obtain additional insights. This combination of experiment and simulations to gather quantitative information on the local density of optical states is of direct relevance for the understanding of fundamental quantum optical processes as well as for the engineering of novel photonic and plasmonic devices.
Photon transport in one-dimensional systems coupled to three-level quantum impurities
We discuss the transport properties of a single photon in a one-dimensional waveguide with an embedded three-level atom and utilize both stationary plane-wave solutions and time-dependent transport calculations to investigate the interaction of a photon with driven and undriven V- and Λ-systems. Specifically, for the case of an undriven V-system, we analyze the phenomenon of long-time occupation of the upper atomic levels in conjunction with almost dark states. For the undriven Λ-system, we find non-stationary dark states and we explain how the photon's transmittance can be controlled by an initial phase difference between the energetically lower-lying atomic states. With regard to the driven three-level systems, we discuss electromagnetically induced transparency in terms of the pulse propagation of a single photon through a Λ-type atom. In addition, we demonstrate how a driven V-type atom can be utilized to control the momentum distribution of the scattered photon.
Strongly coupled slow-light polaritons in one-dimensional disordered localized states
Cavity quantum electrodynamics advances the coherent control of a single quantum emitter with a quantized radiation field mode, typically piecewise engineered for the highest finesse and confinement in the cavity field. This enables the possibility of strong coupling for chip-scale quantum processing, but till now is limited to few research groups that can achieve the precision and deterministic requirements for these polariton states. Here we observe for the first time coherent polariton states of strong coupled single quantum dot excitons in inherently disordered one-dimensional localized modes in slow-light photonic crystals. Large vacuum Rabi splittings up to 311.μeV are observed, one of the largest avoided crossings in the solid-state. Our tight-binding models with quantum impurities detail these strong localized polaritons, spanning different disorder strengths, complementary to model-extracted pure dephasing and incoherent pumping rates. Such disorder-induced slow-light polaritons provide a platform towards coherent control, collective interactions, and quantum information processing.
Low-loss fiber-to-chip couplers with ultrawide optical bandwidth
Providing efficient access from optical fibers to on-chip photonic systems is a key challenge for integrated optics. In general, current solutions allow either narrowband out-of-plane-coupling to a large number of devices or broadband edge-coupling to a limited number of devices. Here we present a hybrid approach using 3D direct laser writing, merging the advantages of both concepts and enabling broadband and low-loss coupling to waveguide devices from the top. In the telecom wavelength regime, we demonstrate a coupling loss of less than -1.8 dB between 1480 nm and 1620 nm. In the wavelength range between 730 nm and 1700 nm, we achieve coupling efficiency well above -8 dB which is sufficient for a range of broadband applications spanning more than an octave. The 3D couplers allow relaxed mechanical alignment with respect to optical fibers, with -1 dB alignment tolerance of about 5 μm in x- and y-directions and -1 dB alignment tolerance in the z-direction of 34 μm. Using automatized alignment, many such couplers can be connected to integrated photonic circuits for rapid prototyping and hybrid integration. © 2019 Author(s).
Resolvent expansion for discrete non-Hermitian resonant systems [Invited]
The linear response of non-Hermitian resonant systems demonstrates various intriguing features such as the emergence of non-Lorentzian lineshapes. Recently, we have developed a systematic theory to understand the scattering lineshapes in such systems and, in doing so, established the connection with the input/output scattering channels. Here, we follow up on that work by presenting a different, more transparent derivation of the resolvent operator associated with a non-Hermitian system under general conditions and highlight the connection with the structure of the underlying eigenspace decomposition. Finally, we also present a simple solution to the problem of self-orthogonality associated with the left and right Jordan canonical vectors and show how the left basis can be constructed in a systematic fashion. Our work provides a unifying mathematical framework for studying non-Hermitian systems such as those implemented using dielectric cavities, metamaterials, and plasmonic resonators.
Natural variability or anthropogenically-induced variation? Insights from 15 years of multidisciplinary observations at the arctic marine LTER site HAUSGARTEN
Time-series studies of arctic marine ecosystems are rare. This is not surprising since polar regions are largely only accessible by means of expensive modern infrastructure and instrumentation. In 1999, the Alfred Wegener Institute, Helmholtz-Centre for Polar and Marine Research (AWI) established the LTER (Long-Term Ecological Research) observatory HAUSGARTEN crossing the Fram Strait at about 79°N. Multidisciplinary investigations covering all parts of the open-ocean ecosystem are carried out at a total of 21 permanent sampling sites in water depths ranging between 250 and 5500 m. From the outset, repeated sampling in the water column and at the deep seafloor during regular expeditions in summer months was complemented by continuous year-round sampling and sensing using autonomous instruments in anchored devices (i.e., moorings and free-falling systems). The central HAUSGARTEN station at 2500 m water depth in the eastern Fram Strait serves as an experimental area for unique biological in situ experiments at the seafloor, simulating various scenarios in changing environmental settings. Long-term ecological research at the HAUSGARTEN observatory revealed a number of interesting temporal trends in numerous biological variables from the pelagic system to the deep seafloor. Contrary to common intuition, the entire ecosystem responded exceptionally fast to environmental changes in the upper water column. Major variations were associated with a Warm-Water-Anomaly evident in surface waters in eastern parts of the Fram Strait between 2005 and 2008. However, even after 15 years of intense time-series work at HAUSGARTEN, we cannot yet predict with complete certainty whether these trends indicate lasting alterations due to anthropologically-induced global environmental changes of the system, or whether they reflect natural variability on multiyear time-scales, for example, in relation to decadal oscillatory atmospheric processes.
Uniform optical gain as a non-Hermitian control knob
Non-Hermitian optics utilizes judicious engineering of the spatial and spectral distribution of gain and loss in order to tailor the behavior of photonic systems in ways that could not be achieved by modulating only the real part of the refractive index. In this respect, a question that has never been addressed is whether a uniform distribution of gain or loss can also lead to nontrivial non-Hermitian effects in linear systems, beyond just signal amplification or decay. Here, we investigate this problem and demonstrate that the application of uniform gain to a symmetric photonic molecule (PM) can reverse the optical energy distribution inside the structure. For a PM composed of two coupled resonators, this translates into changing the optical energy distribution inside the resonators. For a PM formed through scattering or defect-induced intermodal coupling in a ring resonator, the applied gain, despite being uniform and symmetric, can impose a strong chirality and switch the direction of light propagation from dominantly clockwise to dominantly counterclockwise. These predictions are confirmed by using both coupled mode formalism and full-wave finite-element simulations. Our work establishes a different direction in the field of non-Hermitian optics where interesting behavior can be engineered not only by unbalancing the non-Hermitian parameter but also by changing its average value - a feature that was overlooked in previous works.