Environmentally stable black phosphorus saturable absorber for ultrafast laser

Abstract Black phosphorus (BP) attracts huge interest in photonic and optoelectronic applications ranging from passive switch for ultrafast lasers to photodetectors. However, the instability of chemically unfunctionalized BP in ambient environment due to oxygen and moisture remains a critical barrier to its potential applications. Here, the parylene-C layer was used to protect inkjet-printed BP-saturable absorbers (BP-SA), and the efficacy of this passivation layer was demonstrated on the stable and continuous operation of inkjet-printed BP-SA in harsh environmental conditions. BP-SA was integrated in an erbium-doped ring laser cavity and immersed in water at ~60°C during operation for investigation. Mode-locked pulses at ~1567.3 nm with ~538 fs pulse width remained stable for >200 h. The standard deviation of spectral width, central wavelength, and pulse width were 0.0248 nm, 0.0387 nm, and 2.3 fs, respectively, in this period, underscoring the extreme stability of BP-SA against high temperature and humidity. This approach could enable the exploitation of BP-based devices for photonic applications when operating under adverse environmental conditions.This work was supported by the National Natural Science Foundation of China (grants 51778030 and 51978024, Funder Id: http:// dx.doi.org/10.13039/501100001809) and EPSRC (grant EP/L016087/1, Funder Id: http://dx.doi. org/10.13039/501100000266)

102 fs pulse generation from a long-term stable, inkjet-printed black phosphorus-mode-locked fiber laser.

We demonstrate a long-term stable, all-fiber, erbium-doped femtosecond laser mode-locked by a black phosphorus saturable absorber. The saturable absorber, fabricated by scalable and highly controllable inkjet printing technology, exhibits strong nonlinear optical response and is stable for long-term operation against intense irradiation, overcoming a key drawback of this material. The oscillator delivers self-starting, 102 fs stable pulses centered at 1555 nm with 40 nm spectral bandwidth. This represents the shortest pulse duration achieved from black phosphorus in a fiber laser to date. Our results demonstrate the great potential for black phosphorus as an excellent candidate for long-term stable ultrashort pulse generation

High-energy and efficient Raman soliton generation tunable from 1.98 to 2.29 µm in an all-silica-fiber thulium laser system

We demonstrate a compact, all-fiber-integrated laser system that delivers Raman solitons with a duration of ~100 fs and pulse energy of up to 13.3 nJ, continuously wavelength tunable from 1.98 to 2.29 µm via Raman-induced soliton self-frequency shift (SSFS) in a thulium-doped fiber amplifier. We realize a >90% efficiency of Raman conversion, the highest reported value from SSFS-based sources. This enables us to achieve >10 nJ soliton energy from 2.16 to 2.29 µm range, the highest energy demonstrated above 2.22 µm from an SSFS-assisted all-fiber tunable single-soliton-pulse source. Our simple and compact all-fiber tunable laser could serve as an efficient ~2 µm femtosecond source for a wide range of mid-IR applications.National Natural Science Foundation of China (NSFC) (61605122); Shenzhen Science and Technology Program (JCYJ20150324140036862, KQJSCX20160226194031); Natural Science Foundation of Guangdong Province (2016A030310049); Engineering and Physical Sciences Research Council (EPSRC) (EP/L016087/1); European Union’s 7th Framework Programme (631610); Royal Academy of Engineering (Graphlex); Academy of Finland (276376, 284548, 295777, 304666); Tekes (OPEC)

Wavelength and pulse duration tunable ultrafast fiber laser mode-locked with carbon nanotubes.

Ultrafast lasers with tunable parameters in wavelength and time domains are the choice of light source for various applications such as spectroscopy and communication. Here, we report a wavelength and pulse-duration tunable mode-locked Erbium doped fiber laser with single wall carbon nanotube-based saturable absorber. An intra-cavity tunable filter is employed to continuously tune the output wavelength for 34 nm (from 1525 nm to 1559 nm) and pulse duration from 545 fs to 6.1 ps, respectively. Our results provide a novel light source for various applications requiring variable wavelength or pulse duration

Inkjet Printed Large-Area Flexible Few-Layer Graphene Thermoelectrics

Graphene-based organic nanocomposites have ascended as promising candidates for thermoelectric energy conversion. In order to adopt existing scalable printing methods for developing thermostable graphene-based thermoelectric devices, optimizations of both the material ink and the thermoelectric properties of the resulting films are required. Here, inkjet printed large-area flexible graphene thin films with outstanding thermoelectric properties are reported. The thermal and electronic transport properties of the films reveal the so-called phonon-glass electron-crystal character (i.e. electrical transport behaviour akin to that of few-layer graphene flakes with quenched thermal transport arising from the disordered nanoporous structure). As a result, the all-graphene films show a room-temperature thermoelectric power factor of 18.7 µW m−1 K−2, representing over a three-fold improvement to previous solution-processed all-graphene structures. Our demonstration of inkjet printed thermoelectric devices underscores the potential for future flexible, scalable and low-cost thermoelectric applications, such as harvesting energy from body heat in wearable applications.EPSRC (EP/L016087/1) Royal Academy of Engineering (Graphlex

New Approach for Thickness Determination of Solution-Deposited Graphene Thin Films

Solution processing-based fabrication techniques such as liquid phase exfoliation may enable economically feasible utilization of graphene and related nanomaterials in real-world devices in the near future. However, measurement of the thickness of the thin film structures fabricated by these approaches remains a significant challenge. By using surface plasmon resonance (SPR), a simple, accurate, and quick measurement of the deposited thickness for inkjet-printed graphene thin films is reported here. We show that the SPR technique is convenient and well-suited for the measurement of thin films formulated from nanomaterial inks, even at sub-10 nm thickness. We also demonstrate that the analysis required to obtain results from the SPR measurements is significantly reduced compared to that required for atomic force microscopy (AFM) or stylus profilometer, and much less open to interpretation. The gathered data implies that the film thickness increases linearly with increasing number of printing repetitions. In addition, SPR also reveals the complex refractive index of the printed thin films composed of exfoliated graphene flakes, providing a more rigorous explanation of the optical absorption than that provided by a combination of AFM/profilometer and the extinction coefficient of mechanically exfoliated graphene flakes. Our results suggest that the SPR method may provide a new pathway for the thickness measurement of thin films fabricated from any nanomaterial containing inks.We acknowledge Dr. Lauri Riuttanen for the development of the code for the Metropolis fitting algorithm that we have modified for this work. H.J. acknowledges the Jenny ja Antti Wihuri foundation for the funding used for the research visit to Cambridge which facilitated this work. T.A.-O. acknowledges funding from EPSRC grant EP/L016087/1. H.Y. acknowledges funding from China Scholarship Council and Nokia Foundation. G.H. acknowledges funding from Cambridge Trust and China Scholarship Council. S.A. acknowledges the Scientific and Technological Research Council of Turkey (TÜBİTAK). R.C.T.H. acknowledges funding from an EPSRC Cambridge NanoDTC Translational Fellowship (EPSRC grant EP/G037221/1). Z.S. acknowledges funding from the European Union’s Seventh Framework Programme (REA grant agreement No. 631610), the Academy of Finland (Nos.: 276376, 284548, 295777), TEKES (OPEC), Nokia foundation, and Aalto University. T.H. acknowledges funding from RAEng Fellowship (Graphlex)

Parametrizations of Inclusive Cross Sections for Pion Production in Proton-Proton Collisions

Accurate knowledge of cross sections for pion production in proton-proton collisions finds wide application in particle physics, astrophysics, cosmic ray physics and space radiation problems, especially in situations where an incident proton is transported through some medium, and one requires knowledge of the output particle spectrum given the input spectrum. In such cases accurate parametrizations of the cross sections are desired. In this paper we review much of the experimental data and compare to a wide variety of different cross section parametrizations. In so doing, we provide parametrizations of neutral and charged pion cross sections which provide a very accurate description of the experimental data. Lorentz invariant differential cross sections, spectral distributions and total cross section parametrizations are presented.Comment: 32 pages with 15 figures. Published in Physical Review D62, 094030. File includes 6 tex files. The main file is paper.tex which has include statements refering to the rest. figures are in graphs.di

OGLE-2013-BLG-0102LA,B: Microlensing binary with components at star/brown-dwarf and brown-dwarf/planet boundaries

We present the analysis of the gravitational microlensing event OGLE-2013-BLG-0102. The light curve of the event is characterized by a strong short-term anomaly superposed on a smoothly varying lensing curve with a moderate magnification $A_{\rm max}\sim 1.5$. It is found that the event was produced by a binary lens with a mass ratio between the components of $q = 0.13$ and the anomaly was caused by the passage of the source trajectory over a caustic located away from the barycenter of the binary. From the analysis of the effects on the light curve due to the finite size of the source and the parallactic motion of the Earth, the physical parameters of the lens system are determined. The measured masses of the lens components are $M_{1} = 0.096 \pm 0.013~M_{\odot}$ and $M_{2} = 0.012 \pm 0.002~M_{\odot}$, which correspond to near the hydrogen-burning and deuterium-burning mass limits, respectively. The distance to the lens is $3.04 \pm 0.31~{\rm kpc}$ and the projected separation between the lens components is $0.80 \pm 0.08~{\rm AU}$.Comment: 6 figures, 2 tables, ApJ submitte

Black phosphorus ink formulation for inkjet printing of optoelectronics and photonics.

Black phosphorus is a two-dimensional material of great interest, in part because of its high carrier mobility and thickness dependent direct bandgap. However, its instability under ambient conditions limits material deposition options for device fabrication. Here we show a black phosphorus ink that can be reliably inkjet printed, enabling scalable development of optoelectronic and photonic devices. Our binder-free ink suppresses coffee ring formation through induced recirculating Marangoni flow, and supports excellent consistency ( 30 days) oxidation. We demonstrate printed black phosphorus as a passive switch for ultrafast lasers, stable against intense irradiation, and as a visible to near-infrared photodetector with high responsivities. Our work highlights the promise of this material as a functional ink platform for printed devices.Atomically thin black phosphorus shows promise for optoelectronics and photonics, yet its instability under environmental conditions and the lack of well-established large-area synthesis protocols hinder its applications. Here, the authors demonstrate a stable black phosphorus ink suitable for printed ultrafast lasers and photodetectors