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

THz technologies are continuing to develop for a wide set of applications and photonic is seen as a key technology for their development [1,2]. This is mostly due to their relatively high power, coherence and tuneability as well as, through through the development of optical communication, high speed modulation. However, despite these advantages it is clear that for many application and the development of THz technology a smaller footprint and lower power consumption will also be essential. While photonic solutions using discrete components have shown promising results [3], it remains essential to solve these remaining problems. To do so will require integrated photonic solutions as it will naturally offer smaller footprint while some of the losses within a discrete element system could be better managed thus enabling lower power consumption.

Recent development in integrated photonic solutions for THz systems

Introduction With the increasing demand for broadband mobile services such as wireless local area network (LAN), the integration of wireless and optical networks is a potential solution for increasing capacity and mobility. Wireless LAN systems using the IEEE802.11b standard operate around the 2.4 GHz band, while the IEEE802.11a standard operates in the 5.2 GHz band. Propagation of signals at microwave frequencies require the radio base stations to be closely spaced. The greatly increase d number of base stations required to cover a given geographical area and to make these systems commercially available it is important to keep the system cost as low as possible by having simple base stations. Fiber radio (also known as radio over fiber) is an attractive technology which may be employed. The concept of radio over fiber is to transport information over optical fiber by modulating the light with the radio signal. The fiber radio architecture can give several advantages such as reduced complexity at the antenna site, radio carriers can be allocated dynamically to the different antenna sites, transparency and scalabili ty since much of the processing is done at the central site.

Laser diode nonlinearity compensation using feed-forward linearization in a fiber radio system

An exact optical frequency synthesis technique for WDM applications using optical injection locking of a widely tunable sampled grating (SG) DBR laser is reported. In the experimental setup, an optical frequency comb generator produced a comb spectrum over 1 THz span. The SG-DBR laser was found to have a tuning range of 60 nm, controlled by low drive currents on the front and back Bragg mirrors.

Exact optical frequency synthesis over >1 THz using SG-DBR lasers

High speed photodiodes are a key element of numerous photonic systems. With the development of potential applications in the THz range such as sensing, spectroscopy and wireless transmission, devices with integrated antenna covering the frequency range from 0.1 THz to 3 THz will become essential. In this paper we discuss the development of uni-travelling carrier photodiodes with integrated antennas to address that need. In particular we develop the key elements to present a simple design tool for the efficient integration of the device with an antenna. We also present fabricated device results that show the highest figure of merit to date for photonic THz emitters. When integrated with well-matched antennas the devices have achieved record level of power up to 1 THz compared to other published photomixers.

Antenna integrated THz uni-travelling carrier photodiodes (Invited Paper)

We demonstrate effective homodyne optical phase locking to a phase-shift-keying (PSK) signal with residual carrier by exploiting 8b10b coding. Low-penalty transmission over 215 km of installed dispersion-compensated single-mode fibre is demonstrated. © OSA/OFC/NFOEC 2011.

Alwyn J. Seeds

Papers

Recent development in integrated photonic solutions for THz systems

Laser diode nonlinearity compensation using feed-forward linearization in a fiber radio system

Exact optical frequency synthesis over >1 THz using SG-DBR lasers

Antenna integrated THz uni-travelling carrier photodiodes (Invited Paper)

8b10b line coding of PSK signals for effective homodyne coherent detection