There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

On September 14, 2015 at 09:50:45 UTC the two detectors of the Laser Interferometer Gravitational-Wave Observatory simultaneously observed a transient gravitational-wave signal. The signal sweeps upwards in frequency from 35 to 250 Hz with a peak gravitational-wave strain of 1.0×10(-21). It matches the waveform predicted by general relativity for the inspiral and merger of a pair of black holes and the ringdown of the resulting single black hole. The signal was observed with a matched-filter signal-to-noise ratio of 24 and a false alarm rate estimated to be less than 1 event per 203,000 years, equivalent to a significance greater than 5.1σ. The source lies at a luminosity distance of 410(-180)(+160)  Mpc corresponding to a redshift z=0.09(-0.04)(+0.03). In the source frame, the initial black hole masses are 36(-4)(+5)M⊙ and 29(-4)(+4)M⊙, and the final black hole mass is 62(-4)(+4)M⊙, with 3.0(-0.5)(+0.5)M⊙c(2) radiated in gravitational waves. All uncertainties define 90% credible intervals. These observations demonstrate the existence of binary stellar-mass black hole systems. This is the first direct detection of gravitational waves and the first observation of a binary black hole merger.

/pdf/the-observation-of-gravitational-waves-from-a-binary-black-58srpupgg9.pdf

The Observation of Gravitational Waves from a Binary Black Hole Merger

Microwave photonics, which brings together the worlds of radiofrequency engineering and optoelectronics, has attracted great interest from both the research community and the commercial sector over the past 30 years and is set to have a bright future. The technology makes it possible to have functions in microwave systems that are complex or even not directly possible in the radiofrequency domain and also creates new opportunities for telecommunication networks. Here we introduce the technology to the photonics community and summarize recent research and important applications.

Microwave photonics combines two worlds

An overview of analog microwave photonics will be presented. The performance requirements for externally-modulated analog microwave photonic links will be reviewed with specific emphasis placed on modulator efficiency, laser noise, detected photocurrent, and link linearity.

http://ieeexplore.ieee.org/iel5/6387506/6403300/06403360.pdf

Microwave photonics

Microwave frequency synthesis can be realised by mixing the output of two or more DFB lasers injection locked to the same optical comb. The noise and stability problems of this approach are studied.

Microwave frequency synthesis using injection locked laser comb line selection

Ultra fast (< 12 ns, electronics limited) zero frequency error wavelength switching between 30 channels of a dense wavelength division multiplex source is demonstrated using widely tuneable lasers with optical injection phase lock loop control.

Nanosecond switching time, uncooled, zero frequency DWDM source

A 1 Gbps 105.4 GHz wireless link is demonstrated by directly modulating a photonic integrated dual-laser source. A 50 m link is predicted to be able to achieve error free operation using FEC following optimisation.

/pdf/a-1-gbps-105-4-ghz-link-with-a-directly-modulated-photonic-1d8a7q0xvt.pdf

A 1 Gbps 105.4 GHz Link with a Directly Modulated Photonic Integrated Dual Laser Source

Results are presented for analytical computer modelling and experimental studies of optically induced frequency tuning of W-Band (75?110 GHz) impatt oscillators. Predictions from an analytical theory are compared with those from a large-signal time-domain computer model, and the effect of unequal electron and hole ionisation coefficients on the tuning performance is illustrated. Experimental measurements are presented showing an optical tuning range of about 10 MHz for an optically generated current of 20 ?A, and comparisons are made with the theoretical predictions.

Optical control of W-band impatt oscillators

Conventional semiconductor lasers tuned by the carrier-induced effect (CIE) suffer from intrinsically non-uniform optical frequency modulation (FM) response due to the associated thermal effect Electric field effect tuned lasers involving no current injection, offer intrinsically uniform FM response We report the first post-growth band-gap engineered, quantum-confined Stark effect (QCSE) tuned two-section ridge waveguide laser, having the widest and most uniform frequency modulation bandwidth (30 kHz to 6 GHz /spl plusmn/3 dB) yet reported for field effect tuned lasers The uniform FM response is independent of laser output power, and residual intensity modulation is less than 5% for 45 GHz peak frequency deviation

Alwyn J. Seeds

Papers

Microwave frequency synthesis using injection locked laser comb line selection

Nanosecond switching time, uncooled, zero frequency DWDM source

A 1 Gbps 105.4 GHz Link with a Directly Modulated Photonic Integrated Dual Laser Source

Optical control of W-band impatt oscillators

A QCSE tuned laser with uniform frequency modulation response for use in microwave photonics