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

We demonstrated an all-fiber-integrated linearly-polarized picosecond ytterbium-doped master-oscillator power-amplifier system, which yielded 225-W of average output power and the corresponding slope efficiency is 70.5p. The seed source was a compact passively mode-locked polarization-maintaining ytterbium-doped all-fiber oscillator with a pulse duration of 80-ps at 58.2-MHz repetition rate. In combination with two pre-amplifiers and a large-mode-area polarization-maintaining ytterbium-doped all-fiber master amplifier, output pulse energy up to 3.8-μJ with 48.3-kW pulse peak power was obtained without the need of complex free-space coupling and output setups. The polarization extinction ratio were measured to be 14.5 dB and the beam quality M2 factors was less than 1.49 in the both orthogonal directions at maximum output power.

High-power all fiber-integrated linearly polarized picosecond ytterbium-doped master-oscillator power amplifier

We have demonstrated a high-power all-polarization-maintaining thulium-doped all fiber picosecond pulsed master oscillator power amplifier. The thulium-doped all fiber oscillator was mode locked by a semiconductor saturable absorber mirror to generate average output power of 100 mW at a repetition rate of 611.5 MHz in a short linear cavity. The first PM thulium-doped fiber preamplifier produced 4.5 W average output power for 17 W incident pump power, and the pulse width was measured to be 18 ps. In the second PM thulium-doped fiber preamplifier and the final PM thulium-doped fiber power amplifier, a segment of 4.5 m LMA PM thulium-doped double-clad fiber were used as the gain medium. Both the thulium-doped active fiber has a core diameter of 25 μm, a core NA of 0.09, inner cladding diameter of 400 μm and a NA of 0.46. The second PM fiber preamplifier produced 73 W average output power for 135 W incident pump power. In the final PM fiber power amplifier, the maximum average output power was up to 203 W at the available pump power of 300 W, the slope efficiency for the final PM fiber power amplifier was 50.7%. The PER at the highest average output power was measured to be <15 dB. The pulse width was 15 ps and the central wavelength was 1985 nm, which corresponds to peak power 22 kW. To the best of our knowledge, this is the highest average output power ever reported for an all fiber ultra-short-pulsed laser at 2 μm wavelength region.

High-power linearly polarized thulium-doped all-fiber picosecond master-oscillator power-amplifier

We report an ultraviolet-extended supercontinuum generation in silica photonic crystal fiber pumped by a giant-chirped fiber laser. Giant chirp has the function of enhancement of short-wavelength generation and the spectra was extended to 370 nm.

Ultraviolet-extended supercontinuum generation in silica photonic crystal fiber pumped by a giant chirped fiber laser

Hollow-core fiber (HCF) has found plenty of interdisciplinary applications in areas ranging from ultra-intense pulse delivery, single-cycle pulse generation, low latency optical communication, UV light sources, mid-IR gas lasers to biochemical sensing, quantum optics and mid-IR to Terahertz waveguides. These applications calls for better performance HCF, especially in loss, bandwidth and mode quality. Here we present a new hollow-core fiber with conjoined-tubes in the cladding and a negative-curvature core shape. It exhibits a minimum transmission loss of 2 dB/km at 1512 nm and a <16 dB/km bandwidth covering the O, E, S, C, L telecom bands. The debut of this conjoined-tube hollow-core fiber, with combined merits of ultralow loss, broad bandwidth, low bending loss, high mode quality and simple structure heralds a new opportunity to fully unleash the potential of hollow-core fiber in laser and telecommunication related applications.

Ultralow loss hollow-core conjoined-tube negative-curvature fiber

Frequency swept laser sources have various applications, such as LIDAR, spectroscopy, sensing. We demonstrate a 1.5-μm frequency-sweepable single frequency fiber laser in this work. By modulating the intensity of the pump, photo-induced refractive index change occurs in the gain fiber and the free spectral range of the laser is improved. As a result, the frequency sweeping can be realized. The DBR structure is employed to ensure the single-frequency operation. The central wavelength and the maximum sweeping range is measured to be 1550.25nm and 800MHz, respectively. A repetition rate up to 1kHz with an average output power of 0.6mw is realized.

Pu Wang

Papers

High-power all fiber-integrated linearly polarized picosecond ytterbium-doped master-oscillator power amplifier

High-power linearly polarized thulium-doped all-fiber picosecond master-oscillator power-amplifier

Ultraviolet-extended supercontinuum generation in silica photonic crystal fiber pumped by a giant chirped fiber laser

Ultralow loss hollow-core conjoined-tube negative-curvature fiber

A 1.5μm frequency-sweepable single frequency fiber laser