No abstract

Electrons and holes confined in quantum dots define an excellent building block for quantum emergence, simulation, and computation. In order for quantum electronics to become practical, large numbers of quantum dots will be required, necessitating the fabrication of scaled structures such as linear and 2D arrays. Group IV semiconductors contain stable isotopes with zero nuclear spin and can thereby serve as excellent host for spins with long quantum coherence. Here we demonstrate group IV quantum dot arrays in silicon metal-oxide-semiconductor (SiMOS), strained silicon (Si/SiGe) and strained germanium (Ge/SiGe). We fabricate using a multi-layer technique to achieve tightly confined quantum dots and compare integration processes. While SiMOS can benefit from a larger temperature budget and Ge/SiGe can make ohmic contact to metals, the overlapping gate structure to define the quantum dots can be based on a nearly identical integration. We realize charge sensing in each platform, for the first time in Ge/SiGe, and demonstrate fully functional linear and two-dimensional arrays where all quantum dots can be depleted to the last charge state. In Si/SiGe, we tune a quintuple quantum dot using the N+1 method to simultaneously reach the few electron regime for each quantum dot. We compare capacitive cross talk and find it to be the smallest in SiMOS, relevant for the tuning of quantum dot arrays. These results constitute an excellent base for quantum computation with quantum dots and provide opportunities for each platform to be integrated with standard semiconductor manufacturing. * Corresponding Author: m.veldhorst@tudelft.nl arXiv:1909.06575v1 [cond-mat.mes-hall]

We study lasing in distributed feedback lasers made from square lattices of silver particles in a dye-doped waveguide. We present a systematic analysis and experimental study of the band structure underlying the lasing process as a function of the detuning between the particle plasmon resonance and the lattice Bragg diffraction condition. To this end, as gain medium we use either a polymer doped with Rh6G only, or polymer doped with a pair of dyes (Rh6G and Rh700) that act as Förster energy transfer (FRET)-pair. This allows for gain respectively at 590 nm or 700 nm when pumped at 532 nm, compatible with the achievable size-tunability of silver particles embedded in the polymer. By polarization-resolved spectroscopic Fourier microscopy, we are able to observe the plasmonic/photonic band structure of the array, unravelling both the stop gap width, as well as the loss properties of the four involved bands at fixed lattice Bragg diffraction condition and as function of detuning of the plasmon resonance. To explain the measurements we derive an analytical model that sheds insights on the lasing process in plasmonic lattices, highlighting the interaction between two competing resonant processes, one localized at the particle level around the plasmon resonance, and one distributed across the lattice. Both are shown to contribute to the lasing threshold and the overall emission properties of the array.