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Two-dimensional surface-enhanced Raman scattering (SERS) substrates have drawn intense attention due to their excellent spectral reproducibility, high uniformity and perfect anti-interference ability. However, the inferior detection sensitivity and low enhancement have limited the practical application of two-dimensional SERS substrates. To address this issue, we propose that the interaction between the MoTe2 substrate and the analyte rhodamine 6G molecules could be remarkably enhanced by the introduced p-doping effect and lattice distortion of MoTe2 via hydrogen plasma treatment. After the treatment, the SERS is greatly improved, the enhancement factor of probe molecules reaches 1.83 × 106 as well as the limit of detection concentration reaches 10−13 M. This method is anticipated to afford new enhancement probability for other 2D materials, even non-metal oxide semiconductor SERS substrates. [ABSTRACT FROM AUTHOR]

We report a compact high power Tm,Ho:YAG laser nearly at room temperature. The laser-diode side-pumped Tm:YAG and Tm,Ho:YAG laser modules are operated in the same cavity. The laser yields 37.34 W of continuous wave output power under the temperature of 6°C, corresponding to a maximum slope efficiency of 16.7% when the output power lies from 5.1 W to 27.0 W. This is the first report on the combined Tm:YAG and Tm,Ho:YAG lasers for obtaining high power 2.1 μm laser. [ABSTRACT FROM AUTHOR]

We propose and demonstrate a new approach for a high power pulse laser reflection sequence combination with a fast steering mirror (FSM). This approach possesses significant advantages for lasers combining with a variety of output power, wavelength, pulse duration, repetition rates and polarization. The maximum number of laser routes participating in combination principally depends on the FSM’s adjustment time of the step response, lasers’ repetition rates and pulse duration. A proof-of-principle experiment is performed with two 2-kW level pulsed beams. The results indicate that the combined beam has an excellent pointing stability with rms pointing jitter ∼8.5 μrad. Meanwhile, a high combining efficiency of 98.6% is achieved with maintaining good beam quality. [ABSTRACT FROM AUTHOR]

High resolution laser-based angle-resolved photoemission measurements are carried out on an overdoped superconductor Bi2Sr2CaCu2O8+δwith a Tcof 75 K. Two Fermi surface sheets caused by bilayer splitting are clearly identified with rather different doping levels: the bonding sheet corresponds to a doping level of 0.14, which is slightly underdoped while the antibonding sheet has a doping of 0.27 that is heavily overdoped, giving an overall doping level of 0.20 for the sample. Different superconducting gap sizes on the two Fermi surface sheets are revealed. The superconducting gap on the antibonding Fermi surface sheet follows a standard d-wave form while it deviates from the standard d-wave form for the bonding Fermi surface sheet. The maximum gap difference between the two Fermi surface sheets near the antinodal region is ∼2 meV. These observations provide important information for studying the relationship between the Fermi surface topology and superconductivity, and the layer-dependent superconductivity in high temperature cuprate superconductors. [ABSTRACT FROM AUTHOR]

We report a high conversion efficiency Q-switched Nd:YVO4/KTiOAsO4(KTA) intracavity optical parametric oscillator (IOPO) operating near 3.5 μm based on direct 880 nm laser diode (LD) pumping. A maximum average idler output power of 2.6 W with a pulse width of about 7.9 ns is achieved under an absorbed LD power of 45.4 W at a pulse repetition rate (PRR) of 10 kHz. The maximum optical-optical conversion efficiency from LD power to OPO mid-infrared (MIR) output of 6.74% is achieved. To our knowledge, this is the highest conversion efficiency for a KTA-IOPO by exploiting a Q-switched laser as the parent fundamental pump source. The beam quality factors M2of the MIR beam at the full output power with a PRR of 10 kHz are within 2.12 in both the horizontal and vertical directions, indicating a near Gaussian mode. [ABSTRACT FROM AUTHOR]

We demonstrate a high power, high brightness, slab amplifier based on face-pumped Nd:YAG slab gain modules, having a high efficient hybrid cooling system of the conduction cooling and forced convection cooling. Using a single gain module, a laser output power up to 4.5 kW with a remarkable optical-optical conversion efficiency of 51% is realized, indicating an excellent lasing performance of the Nd:YAG slab module. The amplifier operates at a repetition rate of 700 Hz and delivers a maximum average output power exceeding 10.5 kW with pulse duration of 150 μs. A good beam quality factor is measured to be β = 1.9. To the best of our knowledge, this is the highest brightness for a 10 kW level Nd:YAG slab amplifier. [ABSTRACT FROM AUTHOR]

We carry out detailed momentum-dependent and temperature-dependent measurements on Bi2Sr2CaCu2O8+δ (Bi2212) superconductor in the superconducting and pseudogap states by super-high resolution laser-based angle-resolved photoemission spectroscopy. The precise determination of the superconducting gap for the nearly optimally doped Bi2212 (K) at low temperature indicates that the momentum-dependence of the superconducting gap deviates from the standard d-wave form ()). It can be alternatively fitted by including a high-order term ()) in which the next nearest-neighbor interaction is considered. We find that the band structure near the antinodal region smoothly evolves across the pseudogap temperature without a signature of band reorganization which is distinct from that found in Bi2Sr2CuO6+δ superconductors. This indicates that the band reorganization across the pseudogap temperature is not a universal behavior in cuprate superconductors. These results provide new insights in understanding the nature of the superconducting gap and pseudogap in high-temperature cuprate superconductors. [ABSTRACT FROM AUTHOR]

A frequency stabilization approach is introduced for the microsecond pulse sodium beacon laser using an intracavity tilt- and temperature-tuned etalon based on a computer-controlled feedback system connected with a fast high-precision wavelength meter. The frequency stability of the sodium beacon lasers is compared with and without feedback loop controlling. The output wavelength of the laser is locked to the sodium D absorption line (589.159 nm) over 12 h with the feedback loop controlling technology. As a result, the sodium laser guide star is successfully observed by the telescope of National Astronomical Observatories at Xinglong. This approach can also be used for other pulses and continuous-wave lasers for the frequency stabilization. [ABSTRACT FROM AUTHOR]

A high-pulse-energy high-beam-quality tunable Ti:sapphire laser pumped by a frequency-doubled Nd:YAG laser is demonstrated. Using a fused-silica prism as the dispersion element, a tuning range of 740–855 nm is obtained. At an incident pump energy of 774 mJ, the maximum output energy of 104 mJ at 790 nm with a pulse width of 100 μs is achieved at a repetition rate of 5 Hz. To the best of our knowledge, it is the highest pulse energy at 790 nm with pulse width of hundred micro-seconds for an all-solid-state laser. The linewidth of output is 0.5 nm, and the beam quality factor M2 is 1.16. The high-pulse-energy high-beam-quality tunable Ti:sapphire laser in the range of 740–855 nm can be used to establish a more accurate and consistent absolute scale of second-order optical-nonlinear coefficients for KBe2BO3F2 measured in a wider wavelength range and to assess Miller’s rule quantitatively. [ABSTRACT FROM AUTHOR]

The phase stability, thermodynamics properties and electronic structures of L12-Al3Sc and Al3Y compounds under pressure up to 40 GPa are investigated by using first-principles within a local density approximation. The results of formation energies show that Al3Sc is more stable than Al3Y and the stability of Al3Sc will be better with the increasing pressure. The Gibbs free energy, heat capacity, Debye temperature and thermal expansion coefficient are also investigated. The decreasing density of states at the Fermi level and the strengthening Sc/Y-d orbital hybridization with Al (s, p) under high pressure lead to the observed increase of the structural stability for L12-Al3Sc and Al3Y under pressures. [ABSTRACT FROM AUTHOR]

Two-dimensional surface-enhanced Raman scattering (SERS) substrates have drawn intense attention due to their excellent spectral reproducibility, high uniformity and perfect anti-interference ability. However, the inferior detection sensitivity and low enhancement have limited the practical application of two-dimensional SERS substrates. To address this issue, we propose that the interaction between the MoTe2 substrate and the analyte rhodamine 6G molecules could be remarkably enhanced by the introduced p-doping effect and lattice distortion of MoTe2 via hydrogen plasma treatment. After the treatment, the SERS is greatly improved, the enhancement factor of probe molecules reaches 1.83 × 106 as well as the limit of detection concentration reaches 10−13 M. This method is anticipated to afford new enhancement probability for other 2D materials, even non-metal oxide semiconductor SERS substrates. [ABSTRACT FROM AUTHOR]