LD-pumped 6 W cw Tm^3＋-Doped Silica Double-Cladding Fibre Laser

We report a thulium-doped silica fibre laser that generates a maximum cw output power of 6 W in a 2 μm wavelength range when cladding-pumped by a laser diode （LD） operating at approximately 791 nm at room temperature. The slope efficiency with respect to the launched pump power is 50% and 38.4%, with and without an output coupler mirror, respectively. The corresponding thresholds are 2.8 W and 4.8 W, respectively. The beam qualities Mx^2 and My^2 are 1.26 and 1.32, respectively. The experimental results are also analysed.

High Power Continuous-Wave Diode-End-Pumped 1.34-μm Nd：GdVO4 Laser

A high power cw all-solid-state 1.34-μm Nd：GdVO4 laser is experimentally demonstrated. With a diode-double-end-pumped configuration and a simple plane-parallel cavity, a maximum output power of 27.9 W is obtained at incident pump power of 96 W, introducing a slope efficiency of 35.4%. To the best of our knowledge, this is the highest output power of diode-end-pumped 1.3-μm laser. With the experimental data, the thermal-stress- resistance figure of merit of Nd：GdVO4 crystal with 0.3 at% Nd^3＋ doped level is calculated to be larger than 9.94 W/cm.

A Switchable Multi-wavelength Erbium-Doped Photonic Crystal Fiber Laser with Linear Cavity Configuration

A switchable multi-wavelength erbium-doped photonic crystal fiber laser with a linear cavity configuration based on a Sagnac loop mirror is proposed and demonstrated experimentally.The laser is based on saturated spectral hole burning and the polarization hole burning effects can be switched among single-wavelength,dual-wavelength,triple-wavelength and quadruple-wavelength outputs at room temperature.The wavelength period of the output spectrum is easily varied by using polarization maintaining fibers of different lengths.The proposed fiber laser has a signal-to-noise ratio of higher than 30 dB and achieves a low threshold power of 37 mW.The power fluctuations of the lasing lines are less than 0.54 dB,1.7 dB and 2.9 dB when the laser operates at single-wavelength,dual-wavelength and triple-wavelength for one hour.

Q-Switched Thulium-Doped Domestic Silica Fiber Laser

We report a cladding-pumped Tm^(3+)-doped domestic silica fiber laser operated at 2pm and actively Q-switched with an acousto-optic modulator.Pulse trains are obtained as pumped by a 785nm laser diode.The maximum average output power is 1.27W.Peak power up to 4.2kW and pulse energy up to 840μJ are obtained with the pulse duration of 200ns produced at a repetition rate of 1 kHz.The laser performance is studied under different repetition rates and pump powers.Lastly,we give some discussion.

Graphene-Oxide-Based Q-Switched Fiber Laser with Stable Five-Wavelength Operation

We demonstrate an erbium-doped ring-cavity fiber laser Q-switched by a graphene oxide-based saturable absorber(GOSA).The GOSA was fabricated by vertically evaporating GO-polyvinylalcohol(GO/PVA)composite dispersion,and has a good performance under room temperature.Utilizing a specially fabricated fiber Bragg grating(FBG),stable five-wavelength lasing is realized and stabilized at different pump powers under any polarization.When the pump power increases from 78.4 mW to 379.3 mW,the output power ranging from 1.9 mW to 16.6 mW could be obtained,with pulse duration from 6.8μs to 2.72μs,single pulse energy from 123.73 nJ to 229.74 nJ,and pulse repetition rate from 15.36 kHz to 72.25 kHz.To the best of our knowledge,it is the first simultaneous realization of five-wavelength operation and pulse output in a GO Q-switched all fiber laser system.

Integrated System of Solar Cells with Hierarchical NiCo2O4 Battery-Supercapacitor Hybrid Devices for Self-Driving Light-Emitting Diodes

An integrated system has been provided with a-Si/H solar cells as energy conversion device,NiCo2O4 battery-supercapacitor hybrid(BSH)as energy storage device,and light emitting diodes(LEDs)as energy utilization device.By designing three-dimensional hierarchical NiCo2O4 arrays as faradic electrode,with capacitive electrode of active carbon(AC),BSHs were assembled with energy density of 16.6 Wh kg-1,power density of 7285 W kg-1,long-term stability with 100% retention after 15,000 cycles,and rather low self-discharge.The NiCo2O4//AC BSH was charged to 1.6 V in 1 s by solar cells and acted as reliable sources for powering LEDs.The integrated system is rational for operation,having an overall efficiency of 8.1% with storage efficiency of 74.24%.The integrated system demonstrates a stable solar power conversion,outstanding energy storage behavior,and reliable light emitting.Our study offers a precious strategy to design a self-driven integrated system for highly efficient energy utilization.

Supercontinuum Generation in Lithium Niobate Ridge Waveguides Fabricated by Proton Exchange and Ion Beam Enhanced Etching

We report on the fabrication of the lO-mm-long lithium niobate ridge waveguide and its supercontinuum gen- eration at near-visible wavelengths （around 800hm）. The waveguides are fabricated by a combination of MeV copper ion implantation followed by wet etching in a proton exchanged lithium niobate planar waveguide. Using a mode-locked Ti：sapphire laser with a central wavelength of 800nm, the generated broadest supereontinuum through the ridge waveguides spans 302 nm （at -30 dB points）, from 693 to 995 nm. Temporal coherence proper- ties of the supercontinuum are experimentally studied by a Michelson interferometer and the coherence length of the broadest supercontinuum is measured to be 5.2 μm. Our results offer potential for a compact and integrated supercontinuum source for applications including bio-imaging, spectroscopy and optical communication.

A Wide-Band Thulium-Doped Silica Fibre Amplifier

We investigate a silica-based thulium-doped fibre amplifier, which is a promising candidate for an amplifying device in the S band, in detail using a single wavelength upconversion pumping scheme centred at 1064nm. Our experimental results show that in terms of gain and noise figure, the bi-directional pumping scheme is the best one in the three pumping schemes, named forward, backward and hi-directional pumping schemes. The amplifier has a gain not only in the S band, but also in the C band, even in the L band. The gain is above 3dB from 1525nm to 1580nm with a peak of 7.SdB.

High-Stability Superfluorescent Fiber Source Based on an Er3+-Doped Photonic Crystal Fiber

A superfluorescent fiber source (SFS) based on an Er3+-doped photonic crystal fiber (EDPCF) is reported.Owing to the temperature insensitivity of the EDPCF,we show that it is possible to improve the mean wavelength stability of an SFS.Using single-backward configuration,the EDPCF SFS mean wavelength variation at temperatures from -40℃ to 60℃ is less than 100ppm,indicating that the thermal coefficient of the EDPCF is smaller than 1 ppm/℃ and 3-6 times smaller than those of two conventional Er3+-doped fibers under the same experimental conditions.The best performance of the EDPCF-based SFS is obtained between 0℃ and 60℃,at which the change in the mean wavelength is only 17.445 ppm.

H_(2)-Assistance One-Step Growth of Si Nanowires and Their Growth Mechanism

Large-scale nanowires are grown on Si wafers by the catalyst-free one-step thermal reaction method in Ar/H_(2) mixture atmosphere at 1000°C.The x−ray diffraction and energy dispersive x-ray spectroscopy results reveal that the final nanowires are of silicon nanostructures.The field emission scanning electron microscopy shows that these self-organized Si nanowires(SiNWs)possess curly crowns with diameters varying from 10 to 300 nm and lengths of up to several hundreds of micrometers.The transmission electron microscopy indicates that the nanowires are pure Si with amorphous structures.All the measurement results show that no silicon oxide is generated in our products.The growth mechanism is proposed tentatively.Silicon oxide is reduced into Si nanoparticles under the Ar/H_(2) mixture,which is the main reason for the formation of such SiNWs.Our experiments offer a method of preparing Si nanostructures by simply reducing silicon oxide at high temperature.

Ultrafast charge transfer in dual graphene-WS_2 van der Waals quadrilayer heterostructures

Using dual graphene–WS2 quadrilayer heterostructures as an example, we find that the ultrafast transfer of electrons from WS2 to graphene takes place within 114 fs, and the Coulomb field of the charge can effectively affect the interlayer electron transfer. This effect illustrates that the charge transfer in such van der Waals heterostructures may be controlled by an externally applied electric field for promising applications in photoelectric devices.

High-repetition-rate and high-power efficient picosecond thin-disk regenerative amplifier

We present an effective approach to realize a highly efficient,high-power and chirped pulse amplification-free ultrafast ytterbium-doped yttrium aluminum garnet thin-disk regenerative amplifier pumped by a zero-phonon line 969 nm laser diode.The amplifier delivers an output power exceeding 154 W at a pulse repetition rate of 1 MHz with custom-designed 48 pump passes.The exceptional thermal management on the thin disk through high-quality bonding,efficient heat dissipation and a fully locked spectrum collectively contributes to achieving a remarkable optical-to-optical efficiency of 61%and a near-diffraction-limit beam quality with an M2 factor of 1.06.To the best of our knowledge,this represents the highest conversion efficiency reported in ultrafast thin-disk regenerative amplifiers.Furthermore,the amplifier operates at room temperature and exhibits exceptional stability,with root mean square stability of less than 0.33%.This study significantly represents advances in the field of laser amplification systems,particularly in terms of efficiency and average power.This advantageous combination of high efficiency and diffraction limitation positions the thin-disk regenerative amplifier as a promising solution for a wide range of scientific and industrial applications.

Diode-pumped 1123-nm Nd:YAG laser

We demonstrated a diode-pumped Nd:YAG laser with a plano-concave resonator. When the pump power is 1.57 W, the output power of 1123-nm laser is 132 mW at the temperature of 20 ℃, and the power change is less than 2% in an hour. A periodically poled LiNbO3 (PPLN) was used as outer cavity frequency-doubling crystal and 561-nm laser was observed.

Recent development of saturable absorbers for ultrafast lasers [Invited]

As one of the greatest inventions in the 20 th century, ultrafast lasers have offered new opportunities in the areas of basic scientific research and industrial manufacturing. Optical modulators are of great importance in ultrafast lasers, which directly affect the output laser performances. Over the past decades, significant efforts have been made in the development of compact, controllable, repeatable, as well as integratable optical modulators(i.e., saturable absorbers). In this paper, we review the fundamentals of the most widely studied saturable absorbers, including semiconductor saturable absorber mirrors and low-dimensional nanomaterials. Then, different fabrication technologies for saturable absorbers and their ultrafast laser applications in a wide wavelength range are illustrated. Furthermore, challenges and perspectives for the future development of saturable absorbers are discussed and presented. The development of ultrafast lasers together with the continuous exploration of reliable saturable absorbers will open up new directions for the mass production of the nextgeneration optoelectronic devices.

Diode-pumped vertical external cavity surface emitting laser at 1 μm

We demonstrated a diode-pumped vertical external cavity surface emitting laser with simple plane-concave cavity. When the pump power at a wavelength of 811.6 nm is 1.5 W, the maximum output power is 40.4 mW at the wavelength of 1005.8 nm. The optical-optical conversion efficiency is 2.7%. .

High-power MoTe_2-based passively Q-switched erbium-doped fiber laser

Materials in the transition metal dichalcogenide family, including WS2, MoS2, WSe2, and MoSe2, etc., have captured a substantial amount of attention due to their remarkable nonlinearities and optoelectronic properties.Compared with WS2 and MoS2, the monolayered MoTe2 owns a smaller direct bandgap of 1.1 eV. It is beneficial for the applications in broadband absorption. In this letter, using the magnetron sputtering technique, MoTe2 is deposited on the surface of the tapered fiber to be assembled into the saturable absorber. We first implement the MoTe2-based Q-switched fiber laser operating at the wavelength of 1559 nm. The minimum pulse duration and signal-to-noise ratio are 677 ns and 63 dB, respectively. Moreover, the output power of 25 mW is impressive compared with previous work. We believe that MoTe2 is a promising 2D material for ultrafast photonic devices in the high-power Q-switched fiber lasers.

Efficient improvement of 2.7 μm luminescence of Er^(3+):oxyfluoride glass containing gallium by Yb^(3+) ions codoping

Mid-infrared laser materials with low phonon energy have significant applications. However, the development of available glass systems for high-power laser gain medium have posed a great challenge.Therefore, we investigated the 2.7 μm spectroscopic properties of Er^(3+)/Yb^(3+) -codoped oxyfluoride glass containing gallium, which were prepared by typically melting and quenching methods. The 2.7 μm luminescence properties of the Er^(3+)/Yb^(3+)-codoped oxyfluoride glass containing gallium were recorded by a 980 nm laser diode. The Judde Ofelt parameters, decay curves, emission cross section, energy transfer efficiency and quantum efficiency were calculated. The maximum emission cross section of YbFGa-0.5 is 1.63 × 10^(-20) cm^2 by 980 nm excitation. The energy transfer efficiency is calculated to be77.8% for the YbFGa-0.5 glass around 2700 nm. The quantum efficiency at 1530 nm is 65.6%. The result reveals that the best doping concentration ratio of Er^(3+):Yb^(3+) ions is 1:0.5, and suggests an effective energy transfer from Yb^(3+) to Er^(3+) ions.

Terahertz transmission properties of Cr ion implantation glass

Cr ion implantations in glass with the different doses of D=1.493×10^（17） and 4.976×10^（17） ion/cm^2 are obtained by metal vapor vacuum arc（MEVVA）.The effects of the different Cr ion implanted doses on terahertz（THz） transmission property are analyzed from THz time-domain spectroscopy.The results show that the more the Cr ion implanted dose in the micro-area implantation glasses,the larger the THz transmission except the larger absorption at 0.24 THz.This is an effect attributed to the coupling of plasmas on both the implantation and the implantation affected zones of the Cr ion implantation glass.

Reconfigurable,graphene-coated,chalcogenide nanowires with a sub-10-nm enantioselective sorting capability

Chiral surface plasmon polaritons(SPPs)produced by plasmonic nanowires can be used to enhance molecular spectroscopy for biosensing applications.Nevertheless,the switchable stereoselectivity and detection of various analytes are limited by a lack of switchable,chiral SPPs.Using both finite-element method simulations and analytic calculations,we present a graphene-coated chalcogenide(GCC)nanowire that produces mid-infrared,chiral SPPs.The chiral SPPs can be reversibly switched between“on”(transparent)and“off”(opaque)by non-volatile structural state transitions in the dielectric constants of the chalcogenide glass Ge2Sb2Te5.Furthermore,by controlling the Fermi energy of the graphene-coating layer,the nanowire can output either non-chiral or chiral SPPs.A thermal-electric model was built to illustrate the possibility of ultrafast on/off switching of the SPPs at the terminus of the nanowire.Finally,we show that a selective,lateral sorting of sub-10-nm enantiomers can be achieved via the GCC nanowire.Chiral nanoparticles with opposite handedness experience transverse forces that differ in both their sign and magnitude.Our design may pave the way for plasmonic nanowire networks and tunable nanophotonic devices,which require the ultrafast switching of SPPs,and provide a possible approach for a compact,enantiopure synthesis.

Thailand’s amazing diversity:up to 96%of fungi in northern Thailand may be novel

Fungi have been often neglected,despite the fact that they provided penicillin,lovastatin and many other important medicines.They are an understudied,but essential,fascinating and biotechnologically useful group of organisms.The study of fungi in northern Thailand has been carried out by us since 2005.These studies have been diverse,ranging from ecological aspects,phylogenetics with the incorportation of molecular dating,taxonomy(including morphology and chemotaxonomy)among a myriad of microfungi,to growing novel mushrooms,and DNA-based identification of plant pathogens.In this paper,advances in understanding the biodiversity of fungi in the region are discussed and compared with those further afield.Many new species have been inventoried for the region,but many unknown species remain to be described and/or catalogued.For example,in the edible genus Agaricus,over 35 new species have been introduced from northern Thailand,and numerous other taxa await description.In this relatively well known genus,93%of species novelty is apparent.In the microfungi,which are relatively poorly studied,the percentage of novel species is,surprisingly,generally not as high(55–96%).As well as Thai fungi,fungi on several hosts from Europe have been also investigated.Even with the well studied European microfungi an astounding percentage of new taxa(32–76%)have been discovered.The work is just a beginning and it will be a daunting task to document this astonishingly high apparent novelty among fungi.