Chiral emission into nanophotonic resonators

Chiral emission, where the handedness of a transition dipole determines the direction in which a photon is emitted, has recently been observed from atoms and quantum dots coupled to nanophotonic waveguides. Here, we consider the case of chiral light-matter interactions in resonant nanophotonic structures, deriving closed-form expressions for the fundamental quantum electrodynamic quantities that describe these interactions. We show how parameters such as the position dependent, directional Purcell factors and mode volume can be calculated using computationally efficient two dimensional eigenmode simulations. As an example, we calculate these quantities for a prototypical ring resonator with a geometric footprint of only 4.5~$\mu$m$^2$, showing that perfect directionality with a simultaneous Purcell enhancement upwards of 400 are possible. The ability to determine these fundamental properties of nanophotonic chiral interfaces is crucial if they are to form elements of quantum circuits and networks

Sub-radiant states for imperfect quantum emitters coupled by a nanophotonic waveguide

Coherent interactions between quantum emitters in tailored photonic structures is a fundamental building block for future quantum technologies, but remains challenging to observe in complex solid-state environments, where the role of decoherence must be considered. Here, we investigate the optical interaction between two quantum emitters mediated by one-dimensional waveguides in a realistic solid-state environment, focusing on the creation, population and detection of a sub-radiant state, in the presence of dephasing. We show that as dephasing increases, the signatures of sub-radiance quickly vanish in intensity measurements yet remain pronounced in photon correlation measurements, particularly when the two emitters are pumped separately so as to populate the sub-radiant state efficiently. The applied Green's tensor approach is used to model a photonic crystal waveguide, including the dependence on the spatial position of the integrated emitter. The work lays out a route to the experimental realization of sub-radiant states in nanophotonic waveguides containing solid-state emitters.Comment: 12 pages, 7 figure

Философия и интеллект

We use symmetry considerations to understand and unravel near-field measurements, ultimately showing that we can spatially map three distinct fields using only two detectors. As an example, we create 2D field maps of the outof- plane magnetic field and two in-plane fields for a silicon ridge waveguide. Furthermore, we are able to identify and remove polarization mixing of less than 1?30 of our experimental signals. Since symmetries are prevalent in nanophotonic structures and their near-fields, our method can have an impact on many future near-field measurements

Deterministic positioning of nanophotonic waveguides around single self-assembled quantum dots

The capability to embed self-assembled quantum dots (QDs) at predefined positions in nanophotonic structures is key to the development of complex quantum photonic architectures. Here, we demonstrate that QDs can be deterministically positioned in nanophotonic waveguides by pre-locating QDs relative to a global reference frame using micro-photoluminescence ($\mu$PL) spectroscopy. After nanofabrication, $\mu$PL images reveal misalignments between the central axis of the waveguide and the embedded QD of only $(9\pm46$) nm and $(1\pm33$) nm, for QDs embedded in undoped and doped membranes, respectively. A priori knowledge of the QD positions allows us to study the spectral changes introduced by nanofabrication. We record average spectral shifts ranging from 0.1 to 1.1 nm, indicating that the fabrication-induced shifts can generally be compensated by electrical or thermal tuning of the QDs. Finally, we quantify the effects of the nanofabrication on the polarizability, the permanent dipole moment and the emission frequency at vanishing electric field of different QD charge states, finding that these changes are constant down to QD-surface separations of only 70 nm. Consequently, our approach deterministically integrates QDs into nanophotonic waveguides whose light-fields contain nanoscale structure and whose group index varies at the nanometer level.Comment: 26 pages, 9 figures. Updated version of the manuscript, with new appendices and new figure

Quantum optics with near lifetime-limited quantum-dot transitions in a nanophotonic waveguide

Establishing a highly efficient photon-emitter interface where the intrinsic linewidth broadening is limited solely by spontaneous emission is a key step in quantum optics. It opens a pathway to coherent light-matter interaction for, e.g., the generation of highly indistinguishable photons, few-photon optical nonlinearities, and photon-emitter quantum gates. However, residual broadening mechanisms are ubiquitous and need to be combated. For solid-state emitters charge and nuclear spin noise is of importance and the influence of photonic nanostructures on the broadening has not been clarified. We present near lifetime-limited linewidths for quantum dots embedded in nanophotonic waveguides through a resonant transmission experiment. It is found that the scattering of single photons from the quantum dot can be obtained with an extinction of $66 \pm 4 \%$, which is limited by the coupling of the quantum dot to the nanostructure rather than the linewidth broadening. This is obtained by embedding the quantum dot in an electrically-contacted nanophotonic membrane. A clear pathway to obtaining even larger single-photon extinction is laid out, i.e., the approach enables a fully deterministic and coherent photon-emitter interface in the solid state that is operated at optical frequencies.Comment: 27 pages, 7 figure

Dynamical photon-photon interaction mediated by a quantum emitter

Single photons constitute a main platform in quantum science and technology: they carry quantum information over extended distances in the future quantum internet and can be manipulated in advanced photonic circuits enabling scalable photonic quantum computing. The main challenge in quantum photonics is how to generate advanced entangled resource states and efficient light-matter interfaces. Here we utilize the efficient and coherent coupling of a single quantum emitter to a nanophotonic waveguide for realizing quantum nonlinear interaction between single-photon wavepackets. This inherently multimode quantum system constitutes a new research frontier in quantum optics. We demonstrate control of a photon with another photon and experimentally unravel the dynamical response of two-photon interactions mediated by a quantum emitter, and show that the induced quantum correlations are controlled by the pulse duration. The work will open new avenues for tailoring complex photonic quantum resource states

Ultrafast Active Plasmonics on Gold Films

Active plasmonics combines the manipulation of light on both sub-wavelength length and ultrashort time scales, a unique meld that holds promise for developments in many scientific fields. This thesis reports on a novel approach to ultrafast, all-optical control of grating-assisted excitation of surface plasmon polaritons based on opto-thermally modifying the optical properties of gold. In contrast to prior works, this approach results in plasmonic modulation on picosecond and even sub-picosecond time scales, and is compatible with modern, multi-GHz information processing technology. Finally, an analytic model is developed that allows for the rapid and accurate calculation of the coupling efficiency of beams with arbitrary spatial profile. First, the ultrafast dynamics of existing plasmonic coupling resonances, on gold films with grating overlayers, are studied with spectrally resolved pump-probe measurements. Irradiation of the metal by 700 fs, 775 nm laser pulses results in modulations of the plasmonic coupling efficiency of ~20% near the center, or ~60% off-center, of resonances centered between 540 nm and 700 nm. The modulations decay with a time constant of 770 +/- 70 fs. The experimental results are consistent with simulations based on the thermal-dynamics of the electron-lattice gold system, coupled with numerical modeling of light-grating interactions. Next, two 150 fs, 810 nm laser beams are interfered on the surface of a planar gold film, leading to an absorption/refraction grating in the metal. Optical pump-probe spectroscopy measurements of the first (-1) diffracted order in transmission identify plasmonic coupling resonances between 520 nm and 570 nm. The observed coupling efficiency is ~10^{-5}, and the launch window decays with a time constant of 620 +/- 100 fs. Lastly, a Green function-based analytic model is developed to describe grating assisted plasmonic coupling, culminating in a first-order differential equation with coefficients that have both clear physical significance as well as analytic forms. Comparison of this technique with standard numerical modeling methods shows that plasmonic coupling efficiencies in excess of 0.8 are predicted within an error of 15%. This model is used to study plasmonic excitation by finite-size beams, showing the spatial evolution of the intensity of both the surface plasmon polariton and the reflected beam.Ph

Ultrafast tunable optical delay line based on indirect photonic transitions

We introduce the concept of an indirect photonic transition and demonstrate its use in a dynamic delay line to alter the group velocity of an optical pulse. Operating on an ultrafast time scale, we show continuously tunable delays of up to 20 ps, using a slow light photonic crystal waveguide only 300 mu m in length. Our approach is flexible, in that individual pulses in a pulse stream can be controlled independently, which we demonstrate by operating on pulses separated by just 30 ps. The two-step indirect transition is demonstrated here with a 30% conversion efficiency.Publisher PDFPeer reviewe