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Large-scale computer installations are severely limited by network-bandwidth constraints and energy costs that arise from architectural designs originally based on copper interconnects. Wavelength-division multiplexed (WDM) photonic links can increase the network bandwidth but are sensitive to environmental perturbations and manufacturing imperfections that can affect the precise emission wavelength and output power of laser transmitters. Here, we demonstrate a new design of a three-terminal hybrid III–V-on-silicon laser that integrates a metal-oxide-semiconductor (MOS) capacitor into the laser cavity. The MOS capacitor makes it possible to introduce the plasma-dispersion effect and thus change the laser modal refractive index and free-carrier absorption (FCA) loss to tune the laser wavelength and output power, respectively. The approach enables a highly energy efficient method to tune the output power and wavelength of microring lasers, with future prospects for high-speed, chirp-free direct laser modulation. The concept is potentially applicable to other diode laser platforms.

The combination of the long electron state spin coherence time and the optical coupling of the ground electronic states to an excited state manifold makes the nitrogen-vacancy (NV) center in diamond an attractive candidate for quantum information processing. To date the best spin and optical properties have been found in centers deep within the diamond crystal. For useful devices it will be necessary to engineer NVs with similar properties close to the diamond surface. We report on properties including charge state control and preferential orientation for near surface NVs formed either in CVD growth or through implantation and annealing.

The first science run of the LIGO and GEO gravitational wave detectors presented the opportunity to test methods of searching for gravitational waves from known pulsars. Here we present new direct upper limits on the strength of waves from the pulsar PSR J1939+2134 using two independent analysis methods, one in the frequency domain using frequentist statistics and one in the time domain using Bayesian inference. Both methods show that the strain amplitude at Earth from this pulsar is less than a few times 10⁻²².

We develop a detailed spatiotemporal model in the adiabatic approximation of the optical response of the Laser Interferometer Gravitational-Wave Observatory (LIGO) optical system to environmental perturbations. We begin by deriving a first-order linear time-dependent evolution equation that models the electromagnetic field as a function of position within a Fabry–Perot interferometer. This model allows both the length of the resonator and the misalignment angles of the end mirrors to vary in time and describes both resonant and nonresonant phenomena. After defining a biorthogonality relation that must be satisfied by general unperturbed spatial eigenfunctions of the Fabry–Perot interferometer, we expand the intracavity field as a linear combination of these functions and convert the spatiotemporal evolution equation into a linear system of coupled time-dependent iteration and/or differential equations. We then calculate the adiabatic connection equations that link the two LIGO Fabry–Perot interferometers through the power recycling cavity, which comprises two mirrors (the power recycling input mirror and the beam splitter) that have the same mechanical degrees of freedom as those in the Fabry–Perot arm cavities. We develop a detailed instance of this model for the evolution of the intracavity field within a resonator with sufficiently small misalignment angles that a Hermite–Gauss basis set can be used. We develop a detailed general approach to signal demodulation for simulation of servo-control systems and describe its implementation in the Hermite–Gauss approximation for Cartesian split-plane detectors. Finally, we demonstrate the use of this small-angle model to simulate the effect of angular misalignment on the longitudinal response function.

This article discloses two schemes for the efficient distribution of power across nanoscale electronic device architectures using photonic energy. This disclosure also incorporate a method for introducing three-terminal transistor functionality to nanoscale two-terminal devices using photonic gating of the two-terminal devices or arrays of devices. The delivery of power to electronic devices in complex circuit architectures is accomplished through electronic means--electrical-power is provided directly to devices via metallic wires that connect to an electrical power source. As device and wire sizes are reduced to the nanoscale, the resistance of the wires and devices increases very significantly, resulting in problems with lower power efficiency and greater local heating. The scheme for photonic power distribution disclosed herein could entirely overcome the power efficiently and local heating problems, while consuming substantially smaller area of the integrated circuit real estate. The second scheme also addresses the difficulty of introducing three-terminal functionality--and thus gain--into numerous nano- and molecular-electronic device geometries. The second scheme uses a small electrical signal to gate a photonic energy waveguide, which then delivers the photonic energy to a two-terminal junction, providing the sought after three-term functionality.

Using a simple semiclassical model, we explore ultrahigh-resolution optical two-photon spectroscopy of cold neutral atoms falling freely in a fountain. Considering atoms that interact with the same standing-wave laser field twice on their parabolic trajectories, and averaging over a Maxwellian velocity distribution, we predict a nearly Lorentzian line shape with just the natural linewidth. First-order Doppler shifts cancel even if the counterpropagating beams are slightly misaligned, and sub-Hertz resolution appears feasible with a fountain of modest dimensions.