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.

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The Observation of Gravitational Waves from a Binary Black Hole Merger

Our understanding of the cellular implementation of systems-level neural processes like action, thought and emotion has been limited by the availability of tools to interrogate specific classes of neural cells within intact, living brain tissue. Here we identify and develop an archaeal light-driven chloride pump (NpHR) from Natronomonas pharaonis for temporally precise optical inhibition of neural activity. NpHR allows either knockout of single action potentials, or sustained blockade of spiking. NpHR is compatible with ChR2, the previous optical excitation technology we have described, in that the two opposing probes operate at similar light powers but with well-separated action spectra. NpHR, like ChR2, functions in mammals without exogenous cofactors, and the two probes can be integrated with calcium imaging in mammalian brain tissue for bidirectional optical modulation and readout of neural activity. Likewise, NpHR and ChR2 can be targeted together to Caenorhabditis elegans muscle and cholinergic motor neurons to control locomotion bidirectionally. NpHR and ChR2 form a complete system for multimodal, high-speed, genetically targeted, all-optical interrogation of living neural circuits.

Multimodal fast optical interrogation of neural circuitry

* The only book describing applications of nonlinear fiber optics * Two new chapters on the latest developments: highly nonlinear fibers and quantum applications* Coverage of biomedical applications* Problems provided at the end of each chapterThe development of new highly nonlinear fibers - referred to as microstructured fibers, holey fibers and photonic crystal fibers - is the next generation technology for all-optical signal processing and biomedical applications. This new edition has been thoroughly updated to incorporate these key technology developments.The book presents sound coverage of the fundamentals of lightwave technology, along with material on pulse compression techniques and rare-earth-doped fiber amplifiers and lasers. The extensively revised chapters include information on fiber-optic communication systems and the ultrafast signal processing techniques that make use of nonlinear phenomena in optical fibers.New material focuses on the applications of highly nonlinear fibers in areas ranging from wavelength laser tuning and nonlinear spectroscopy to biomedical imaging and frequency metrology. Technologies such as quantum cryptography, quantum computing, and quantum communications are also covered in a new chapter.This book will be an ideal reference for: RD scientists involved with research on fiber amplifiers and lasers; graduate students and researchers working in the fields of optical communications and quantum information. * The only book on how to develop nonlinear fiber optic applications* Two new chapters on the latest developments; Highly Nonlinear Fibers and Quantum Applications* Coverage of biomedical applications

Applications of nonlinear fiber optics

Under strong laser radiation, a Dirac material, the topological insulator (TI) Bi2Te3, exhibits an optical transmittance increase as a result of saturable absorption. Based on an open-aperture Z-scan measurement at 1550 nm, we clearly show that the TI, Bi2Te3 under our investigation, is indeed a very-high-modulation-depth (up to 95%) saturable absorber. Furthermore, a TI based saturable absorber device was fabricated and used as a passive mode locker for ultrafast pulse formation at the telecommunication band. This contribution unambiguously shows that apart from its fantastic electronic property, a TI (Bi2Te3) may also possess attractive optoelectronic property for ultrafast photonics.

Ultra-short pulse generation by a topological insulator based saturable absorber

The emergence of novel two-dimensional (2D) monoelemental materials (Xenes) has shown remarkable potential for their applications in different fields of technology, as well as addressing new discoveries in fundamental science. Xenes (e.g., borophene, silicene, germanene, stanene, phosphorene, arsenene, antimonene, bismuthene, and tellurene) are of particular interest because they are the most chemically tractable materials for synthetic exploration. Owing to their excellent physical, chemical, electronic and optical properties, Xenes have been regarded as promising agents for biosensors, bioimaging, therapeutic delivery, and theranostics, as well as in several other new bio-applications. In this tutorial review, we summarize their general properties including the classification of Xenes according to their bulk properties. The synthetic and modification methods of Xenes are also presented. Furthermore, the representative Xene nanoplatforms for various biomedical applications are highlighted. Finally, research progress, challenges, and perspectives for the future development of Xenes in biomedicines are discussed.

Emerging two-dimensional monoelemental materials (Xenes) for biomedical applications

The invention provides a high-power ultra-short pulse flexible transmission system comprises a laser incident end, a first optical fiber connector, a hollow-core anti-resonant optical fiber and a second optical fiber connector which are sequentially arranged. The laser incident end comprises a coupling device and a focusing lens. After a laser beam is coupled through the coupling device, the laserbeam passes through the focusing lens. An axis of the focusing lens and an axis of the first optical fiber connector overlap, and the first optical fiber connector, the hollow-core anti-resonant optical fiber and the second optical fiber connector are sequentially connected. By coupling light into the hollow-core anti-resonant optical fiber for transmission, the coupling efficiency is high, the light is propagated in an optical fiber core, the optical fiber core can be filled with an inert gas through the optical fiber connectors, and the influences of material absorption and a non-linearityeffect are prevented.

High-power ultra-short pulse flexible transmission system based on hollow-core anti-resonant optical fiber

We demonstrated a high-power single-frequency, single-polarization, thulium-doped all-fiber MOPA system. The linearly-polarized thulium-doped fiber MOPA yielded 192 W of single-frequency output at central wavelength of 2001 nm with a polarization extinction ratio of >15 dB.

High-power Single-frequency, Single-polarization, Thulium-doped all-fiber MOPA

We present a hybrid chirped pulse amplification (CPA) laser system based on Yb-doped fiber and Yb:YAG thin rod. The laser system demonstrates a novel approach to generate high average power up to the 100-W level by using a Yb:YAG thin rod without pump guiding at room temperature. A Yb-doped all-fiber laser with an output power of 7 W and a repetition rate of 1 MHz is amplified to an output power of 126.2 W in simple and compact two-stage amplifiers consisting of a single fiber crystal (SCF) and a Yb:YAG thin rod. To the best of our knowledge, this is the highest output power of Yb:YAG thin-rod amplifier with good beam quality obtained without pump guiding at room temperature. After using a thin-film polarizer (TFP) to remove the thermal depolarization, a linearly polarized ultrashort pulse laser with an average power of 115.2 W is obtained. An output power of 80.6 W with a pulse width of 580 fs is achieved after pulse compression. The central pulse contains 84.1% of the total pulse energy, corresponding to a pulse peak power of 116.9 MW.

Compact 80 W, 1 MHz Femtosecond Chirped Pulse Amplification Laser System Based on a Yb-Doped Fiber and a Yb:YAG Thin Rod

Since the first report of graphene-based ultrafast erbium-doped fiber laser in 2009 [1], most of follow-up studies have been concentrated on performance optimization and improvement of graphene saturable absorber mode-locked or Q-switched lasers at 1.5µm wavelength-band. By contrast, fewer studies have been reported on other wavelengths although graphene based saturable absorber has a distinguished advantage : a broad wavelength-independent saturable absorption range, which covers the wavelength from visible to mid-IR. More recently, a study on graphene mode-locked Yb-doped fiber laser at 1.07µm has been reported [2]; the average output power was about 0.37mW at repetition frequency of 0.9MHz, corresponding to single pulse energy of 0.41nJ. Here, we report much higher pulse energy generation at 1.07µm from an Yb-doped double-clad fiber laser mode-locked by a graphene-deposited broadband reflective mirror in a ring cavity. The average output power is 170mW and the repetition rate is 1.04MHz, corresponding to single pulse energy of 163nJ.

High-energy all-normal-dispersion graphene mode-locked Yb-doped fiber laser

High pulse-energy Yb-doped all-fiber dual-cavity laser with large core-diameter fiber-based passive Q-switch is demonstrated. The monolithic fiber oscillator can generate stable pulses with peak power of 3.4 kW and single pulse energy of 484 μJ.

Pu Wang

Papers

High-power ultra-short pulse flexible transmission system based on hollow-core anti-resonant optical fiber

High-power Single-frequency, Single-polarization, Thulium-doped all-fiber MOPA

Compact 80 W, 1 MHz Femtosecond Chirped Pulse Amplification Laser System Based on a Yb-Doped Fiber and a Yb:YAG Thin Rod

High-energy all-normal-dispersion graphene mode-locked Yb-doped fiber laser

High Pulse-energy Generation from a Monolithic Yb-doped All-fiber Dual-cavity Laser with Fiber-based Passive Q-switch