Showing papers by "Khaled Karrai published in 2009"
TL;DR: A summary of the current state of optomechanics of deformable optical cavities can be found in this article, where the authors identify some of the most important recent developments in the field.
Abstract: Resonant optical cavities such as Fabry–Perot resonators or whispering-gallery structures are subject to radiation pressure pushing their reflecting 'walls' apart. Deformable optical cavities yield to this pressure, but in doing so they in turn affect the stored optical energy, resulting in an optical back-action. For such cavities the optics and the mechanics become strongly coupled, making them fascinating systems in which to explore theories of measurements at the quantum limit. Here we provide a summary of the current state of optomechanics of deformable optical cavities, identifying some of the most important recent developments in the field.
374 citations
TL;DR: The results demonstrate that a hole spin in a quantum dot is highly coherent, and the strategy of using holes instead of electrons may provide a solution to the decoherence problem.
Abstract: Semiconductors have uniquely attractive properties for electronics and photonics. However, it has been difficult to find a highly coherent quantum state in a semiconductor for applications in quantum sensing and quantum information processing. We report coherent population trapping, an optical quantum interference effect, on a single hole. The results demonstrate that a hole spin in a quantum dot is highly coherent.
313 citations
TL;DR: It is shown that the optical transmission of the cavity is affected not only by the static position of the nanorod but also by its vibrational fluctuation, which has implications for a broad range of sensing applications.
Abstract: Confining a laser field between two high reflectivity mirrors of a high-finesse cavity can increase the probability of a given cavity photon to be scattered by an atom traversing the confined photon mode. This enhanced coupling between light and atoms is successfully employed in cavity quantum electrodynamics experiments and led to a very prolific research in quantum optics. The idea of extending such experiments to sub-wavelength sized nanomechanical systems has been recently proposed in the context of optical cavity cooling. Here we present an experiment involving a single nanorod consisting of about 10^9 atoms precisely positioned to plunge into the confined mode of a miniature high finesse Fabry-Perot cavity. We show that the optical transmission of the cavity is affected not only by the static position of the nanorod but also by its vibrational fluctuation. While an imprint of the vibration dynamics is directly detected in the optical transmission, back-action of the light field is also anticipated to quench the nanorod Brownian motion. This experiment shows the first step towards optical cavity controlled dynamics of mechanical nanostructures and opens up new perspectives for sensing and manipulation of optomechanical nanosystems.
99 citations
TL;DR: In this paper, a single nanorod consisting of about 109 atoms precisely positioned into the confined mode of a miniature high finesse Fabry-Perot microcavity was used to study the effect of vibrational fluctuation on the optical transmission of the cavity.
Abstract: The idea of extending cavity quantum electrodynamics experiments to sub-wavelength sized nanomechanical systems has been recently proposed in the context of optical cavity cooling and optomechanics of deformable cavities. Here we present an experiment involving a single nanorod consisting of about 109 atoms precisely positioned into the confined mode of a miniature high finesse Fabry-Perot microcavity. We show that the optical transmission of the cavity is affected not only by the static position of the nanorod but also by its vibrational fluctuation. The Brownian motion of the nanorod is resolved with a displacement sensitivity of 200 fm/√Hz at room temperature. Besides a broad range of sensing applications, cavity-induced manipulation of optomechanical nanosystems and back-action is anticipated.
83 citations
TL;DR: In this article, an optical write-store-read process was demonstrated in a single InGaAs quantum dot within a charge-tunable device, where a single dark exciton was created by nongeminate optical excitation allowing a dark-exciton-based memory bit to be stored for over ∼1μs.
Abstract: An optical write-store-read process is demonstrated in a single InGaAs quantum dot within a charge-tunable device. A single dark exciton is created by nongeminate optical excitation allowing a dark exciton-based memory bit to be stored for over ∼1 μs. Read-out is performed with a gigahertz bandwidth electrical pulse, forcing an electron spin-flip followed by recombination as a bright neutral exciton, or by charging with an additional electron followed by a recombination as a negative trion. These processes have been used to determine accurately the dark exciton spin-flip lifetime as it varies with static electric field.
44 citations
TL;DR: In this article, it was shown that the zero-phonon line (ZPL) is tempera-ture broadened due to acoustic phonon scattering, with a certain threshold or activation energy which corresponds to a phonon mediated excitation of the electron or hole into an excited state.
Abstract: Self-assembled semiconductor quan-tum dots (QDs) exhibit the remarkable spectral feature of optical resonance linewidths (1 3µeV)- far below the thermal energy (362µeV at 42K). [1]. The small linewidth corresponds to the long coherence time of the exciton in the quantum dot of up to a1ns [2]. The strong confinement of the excitons in the QD and the resulting large intraband level spacing of several meVs [3–5] suppress the interac-tion of the electronic states in the QD with the solid crystal lattice of the host material. This remarkable feature shows a close resemblance between atom and QD optics. Many of the proposed applications of QDs in the fields of quantum communication and quantum information processing are based on these atom like optical properties. However, de-spite the importance of dephasing mechanisms for the ap-plication of solid state quantum systems in novel quantum-electronic devices, there is still no consistent microscopic picture of their temperature dependence. The optical spectra of strongly confined electronic sys-tems (QDs or molecules) are expected to show two spectral features. The so called zero-phonon line (ZPL) is tempera-ture broadened due to acoustic phonon scattering, with a certain threshold or activation energy which corresponds to a phonon mediated excitation of the electron or hole into an excited state. These mechanisms correspond to pure dephasing and hence to a lorentzian lineshape of the reso-nance. Apart from the ZPL, there are phonon sidebands which correspond to a mixing of the excitonic states with phonon modes: the absorption or emission of a photon in the QD leading to creation or recombination of an exciton involves the emission or absorption of acoustic phonons. In molecular spectroscopy, this is known as the Frank–Condon principle. In QD spectroscopy the ZPL and phonon sidebands have been observed in non-linear spectroscopy (four-wave-mixing) on an ensemble of InGaAs dots [2]. However, only at temperatures above 50 K the phonon sidebands contributed significantly to the spectra [2]. In PL experi-ments, the observation of phonon sidebands was reported on single CdTe QDs [6] which exhibit a stronger coupling to phonons than III–V semiconductors. In PL spectroscopy on single InGaAs QDs however, only a linear increase of the linewidth of the ZPL was reported without any signifi-cant phonon sidebands [7–10]. This can most probably be
8 citations