Tunable backaction of a DC SQUID on an integrated micromechanical resonator

We have measured the backaction of a dc superconducting quantum interference device (SQUID) position detector on an integrated 1?MHz flexural resonator. The frequency and quality factor of the micromechanical resonator can be tuned with bias current and applied magnetic flux. The backaction is caused by the Lorentz force due to the change in circulating current when the resonator displaces. The experimental features are reproduced by numerical calculations using the resistively and capacitively shunted junction model.     

Linearly polarized 100-kW-Peak-power pulsed fiber laser with a novel master oscillator

We report progress in the design and fabrication of a monolithic, linearly polarized, pulsed, Yb-doped fiber laser. This laser has a peak power of more than 100 kW, a tunable repetition rate from 100 kHz to 1 MHz, a tunable pulse duration from 2 ns to 2.5 μs, and a diffraction-limited, linearly polarized output beam with a mean power of 21 W and a wavelength of 1064 nm. A seed source that consists of a microchip Nd:YVO₄ laser and an electro optic deflector is developed. Using this source, the repetition rate and pulse duration are varied independently of each other. In addition, an excellent pulse-to-pulse repeatability is achieved.     

Olefin Bifunctionalization: A Visible‐light Photoredox‐catalyzed Aryl Alkoxylation of Olefins

Olefin bifunctionalization is a facile route to obtain complex molecules from abundant and commercially available olefin feedstocks. Visible light together with a catalytic amount of tris(bipyridine)ruthenium salt catalyzes the aryl alkoxylation of styrenes with aryl diazonium salts in alcohol solvents via a photoredox process. The scope of this proposed reaction with respect to various aryl diazonium salts and styrenes has been investigated.     

μ-PIV measurements of the ensemble flow fields surrounding a migrating semi-infinite bubble

Microscale particle image velocimetry measurements of ensemble flow fields surrounding a steadily migrating semi-infinite bubble through the novel adaptation of a computer controlled linear motor flow control system. The system was programmed to generate a square wave velocity input in order to produce accurate constant bubble propagation repeatedly and effectively through a fused glass capillary tube. We present a novel technique for re-positioning of the coordinate axis to the bubble tip frame of reference in each instantaneous field through the analysis of the sudden change of standard deviation of centerline velocity profiles across the bubble interface. Ensemble averages were then computed in this bubble tip frame of reference. Combined fluid systems of water/air, glycerol/air, and glycerol/Si-oil were used to investigate flows comparable to computational simulations described in Smith and Gaver III (J Fluid Mech 601:1–23, 2008) and to past experimental observations of interfacial shape. Fluorescent particle images were also analyzed to measure the residual film thickness trailing behind the bubble. The flow fields and film thickness agree very well with the computational simulations as well as existing experimental and analytical results. Particle accumulation and migration associated with the flow patterns near the bubble tip after long experimental durations are discussed as potential sources of error in the experimental method.     

Growth and properties of semi-polar GaN on a patterned silicon substrate

Adopting anisotropy etching method, a (1 1 1) facet of Si is obtained on a Si substrate and selective area growth (SAG) of GaN is performed with metal-organic vapor phase epitaxy on the facet. The epitaxial lateral overgrowth of (1 1¯ 0 1), (1 1 2¯ 2) GaN is investigated on (0 0 1) and (1 1 3) Si substrate, respectively, and the incorporation properties of Si, C, and Mg elements are discussed in relation to the atomic configuration on the surface. Analyzing the optical and electrical properties of C-doped (1 1¯ 0 1) GaN layer, it is shown that carbon creates a shallow acceptor level. On the thus prepared (1 1¯ 0 1) GaN layer, a light emitting diode (LED) with a C-doped p-type layer is fabricated.     

A novel two-stage deep learning-based small-object detection using hyperspectral images

Optical Review - Hyperspectral imaging has drawn significant attention in recent years, and its application to object detection and classification is currently an important research topic. However,...     

High power narrow linewidth laser at 556 nm for magneto-optical trapping of ytterbium

We present a high-power and narrow-linewidth laser for intercombination magneto-optical trapping of ytterbium (Yb) atoms using the 6s^{2 1}S₀–6s6p ³P₁ transition. The system generates 415 mW of continuous wave laser radiation at 556 nm with a linewidth of less than 100 kHz. It is based on a commercial 1 W fiber laser with a frequency doubling stage. Up to 58% frequency doubling efficiency is obtained at an input power of 0.5 W by using a lithium triborate crystal as a nonlinear medium. The system has been successfully used for laser cooling of Yb atoms. PACS  42.55.Wd; 42.60.By; 42.79.Nv