Enhanced spontaneous emission from quantum dots in short photonic crystal waveguides

We report a study of the quantum dot (QD) emission in short photonic crystal waveguides. We observe that the quantum dot photoluminescence intensity and decay rate are strongly enhanced when the emission energy is in resonance with Fabry-Perot (FP) cavity modes in the slow-light regime of the dispersion curve. The experimental results are in agreement with previous theoretical predictions and are further supported by three-dimensional finite element simulations. Our results show that the combination of slow group velocity and Fabry-Perot cavity resonance provide an avenue to efficiently channel photons from quantum dots into waveguides for integrated quantum photonic applications. (C) 2012 American Institute of Physics. [doi:10.1063/1.3683541]

Subwavelength Metallic Structures for Sensing

Qing Tan

Following rapid developments in biotechnology and medicine, optical sensing promises to be extremely important in various applications such as drug discovery, environmental monitoring, etc. Refractive index (RI) based optical sensing is straightforward to monitor or analyze the physical and chemical properties of substances. Among diverse configurations developed for RI detection, plasmonics devices using nanoscale patterned metals are particularly promising. Nano-structured metallic devices enable field confinement in a volume smaller than the diffraction limit. Moreover, they present possibilities for device miniaturization and sensor multiplexing on the same substrate. This thesis is dedicated to investigating a sensing platform combining nanostructured metallic cavities and dielectric waveguides. Periodically structured Au films have been explored for their application in local RI sensing. Two structures are considered: the slot waveguide cavity (SWC) and the annular aperture array (AAA). The SWC is composed of a Au film structured by a periodic slot array, which is deposited on a silicon (Si) waveguide. The evanescent field overlap correlates the resonant optical response of the cavity to the transmission spectrum of the Si waveguide. Theoretical studies, fabrication and characterization have been performed to verify the RI sensing ability for extremely subwavelength slot dimensions (30 nm slot width for 20 nm-thick Au film and 700 nm cavity length). The experimental sensitivity, 730 ± 10 nm/RIU, corresponds to the theory and an optimum resolution of 5.8 × 10-5 RIU is anticipated for RI detection. For the AAA device, the patterned Au film is directly embedded in a Si3N4 waveguide. The Fabry-Pérot-like resonance of the Au cavity results in a resonant reflection, enabling a device sensitive to RI variations. For a wide range of analytes, the theoretical sensitivity is 764 nm/RIU in the near-infrared wavelength range. Compared with other resonance based photonic sensors, the two devices exhibit comparable sensitivities to the RI variation. The small metallic cavity implies a local detection on nano scale and the sample volume can be on the order of a femtolitre. Furthermore, the planar configuration permits easy integration with other photonic devices. Parallel sensing using compatible sensors on the same substrate is anticipated for the realization of portable and low-cost sensor systems.

EPFL2012

Toward Bright and Pure Single Photon Emitters at 300 K Based on GaN Quantum Dots on Silicon

Raphaël Butté, Gordon Jens Callsen, Nicolas Grandjean, Kanako Shojiki, Johann Nicolaï Stachurski, Sebastian Pascal Tamariz Kaufmann

Quantum dots (QDs) based on III-nitride semi-conductors are promising for single photon emission at noncryogenic temperatures due to their large exciton binding energies. Here, we demonstrate GaN QD single photon emitters operating at 300 K with g((2)) (0) = 0.17 +/- 0.08. At this temperature, single photon emission rates up to 10 6 s(-1) are reached, while g((2)) (0)

AMER CHEMICAL SOC2020

Growth and characterization of single quantum dot devices for fiber-based quantum communications

Blandine Alloing

Single photon sources have recently attracted significant interest for their potential role in the future applications of quantum cryptography, and in the longer term, quantum computing. Among the different types of single photon emitters, semiconductor quantum dots (QDs) are good candidates as they combine discrete electronic transitions with the possibility of electrical excitation. Self-assembled InAs QDs on GaAs substrate are by far the most studied system as they can easily be grown into a microcavity structure. Embedding these into a microcavity is important as it increases the extraction efficiency, directionality and speeds up the photon emission. Until now, most studies have concentrated on QDs emitting in the λ

EPFL2006

Subwavelength Metallic Structures for Sensing

Qing Tan

EPFL2012