Subregional parabolic conformal multi-order OAM-generating transmitarray with a novel C-I-shaped grating cell.

A parabolic conformal multi-order OAM-generating transmitarray with novel C-I-shaped grating cell is presented in this paper. The novel cell is composed of three layers of the upper and lower grating structures, and the C-I-shaped metal in the middle layer. Compared with the traditional C-shaped structure, the novel cell can be adjusted to cover 360° transmission phase change with high transmission coefficient at the frequency band of 10-20 GHz.

High power single-frequency 1112 nm laser by an insertable Nd:YAG/YAG bonded monolithic planar ring oscillator.

A high power single-frequency operation at 1112 nm with novel insertable monolithic planar ring oscillator based on a Nd:YAG/YAG bonded crystal is proposed. In a proof-of-principle experiment, a finely designed coating on the output surface is carried out to ensure single-wavelength oscillation at 1112 nm, together with a half-wave plate and a TbGaO crystal inserted in the open space of the bonded block to realize the unidirectional operation with power scalability. Consequently, the single-frequency laser delivers an output power of 3.

Sub-pm linewidth, high pulse energy, high beam quality microsecond-pulse Ti:sapphire laser at 766.699 nm.

In this letter, a sub-pm linewidth, high pulse energy and high beam quality microsecond-pulse 766.699 nm Ti:sapphire laser pumped by a frequency-doubled Nd:YAG laser is demonstrated. At an incident pump energy of 824 mJ, the maximum output energy of 132.

Early arrival did not ensure the early acquisition of intravenous thrombosis for acute ischemic stroke during the COVID-19 pandemic.

Background: Intravenous thrombolysis (IVT) in acute ischemic stroke (AIS) is a time-dependent treatment with a narrow therapeutic time window, in which the time delay could result from the deadline effect.

Methods: One hospital-based cohort was recruited to detect the factors contributing to the deadline effect, where patients with the deadline effect were defined as those who were presented with the onset-to-door time (ODT) in the first 50%, while the door-to-needle time (DNT) was in the last quartile. DNT (in-hospital delay) was further subdivided into several time intervals [door-to-examination time (DET), door-to-imaging time (DIT), door-to-laboratory time (DLT), and decision-making time (DMT) of the patients or their proxies.

Compact integrated aberration-compensating module for a 9 kW Nd:YAG slab laser based on an off-axis stable-unstable resonator.

An integrated aberration-compensating module (IACM), consisting mainly of an adjustable slab-aberration compensator, a one-dimensional Shack-Hartmann wavefront sensor, and a data processor, which meet the urgent requirements of correcting the specific wavefront aberrations of a slab laser based on an off-axis stable-unstable resonator, is designed and experimentally demonstrated. Benefits include compactness, robustness, simplicity, automation, and cost-effectiveness. The particular wavefront aberrations of the 9 kW level quasi-continuous-wave Nd:YAG slab laser, which have characteristics of asymmetry, large amplitude and gradient, high spatial frequency, and low temporal frequency, were measured and theoretically analyzed.

Four decades of hydrological response to vegetation dynamics and anthropogenic factors in the Three-North Region of China and Mongolia.

Afforestation has been initiated in Northeast Asia to improve ecological status. The responses of the regional hydrological cycle to vegetation restoration remain insufficiently explored. This study uses a variety of satellite-derived vegetation variables and hydrological cycle components to scan the eco-hydrological regimes in the Three-North Region of China and Mongolia during the past four decades.

Compact 200 W level linearly polarized microsecond-pulse Nd:YAG oscillator with nearly diffraction-limited beam quality.

A compact 200 W level diode-side-pumped microsecond (µs) pulse linearly polarized rod Nd:YAG laser oscillator was demonstrated with nearly diffraction-limited beam quality. The oscillator was based on a thermally near-unstable cavity design with two concave lenses in the cavity to enlarge the volume of the fundamental mode, leading to improvement of the laser efficiency and beam quality. Consequently, a record-high average power of 222 W was obtained at a repetition rate of 400 Hz with a 180 µs pulse width, corresponding to an optical-to-optical (o-o) conversion efficiency of 37%.

QCW surface-pumped cryogenically cooled single-slab laser with 1 kW level at 946 nm.

We present a kilowatt-level quasi-continuous-wave (QCW) cryogenically cooled 946-nm slab laser oscillator for the first time, to the best of our knowledge. The laser system is based on a double-face-pumped large-size single-slab Nd:YAG design, delivering a record-high average power of 1.06 kW without additional amplification.

1.53 W all-solid-state nanosecond pulsed mid-infrared laser at 6.45 µm.

A compact and robust all-solid-state mid-infrared (MIR) laser at 6.45 µm with high average output power and near-Gaussian beam quality is demonstrated. A maximum output power of 1.

Numerical study on the influence of the linewidth of a QCW pulsed sodium laser on the brightness of a guide star.

In this paper, we investigated the impact of the linewidth of a QCW pulsed sodium laser on the brightness performance of a generating sodium laser guide star by using the numerical simulation tool PRS. We compared the field test results with the simulation results for two TIPC's 30W class sodium guide star lasers and found the results are in good agreement which proves the tool can be used for prediction. Then, we used the tool to study the influence of D2b repumping and different linewidths from 10MHz to 1GHz on the coupling efficiency and the photon return flux.

2.55 W continuous-wave 378 nm laser by intracavity frequency doubling of a diode-pumped Alexandrite laser.

A high-power continuous-wave (CW) ultraviolet (UV) laser at 378 nm from an intracavity frequency-doubled Alexandrite laser has been demonstrated with 638 nm fiber-coupled laser diodes as the pump source. A maximum output power of 2.55 W was obtained, which is the highest power for CW frequency-doubled Alexandrite lasers, to the best of our knowledge, corresponding to the optical-to-optical conversion efficiency of 7.

Excellent performance of a cryogenic Nd:YAlO laser with low wavefront distortion based on zero thermal expansion.

High-power solid-state lasers with good beam quality are attracting great attention on account of their important applications in industry and military. However, the thermal effects generated in the laser host materials seriously limit power scaling and degrade the beam quality. Thermal lensing and thermally induced wavefront deformation are the main causes of the beam quality deterioration.

22.9 W CW single-frequency laser at 671 nm by frequency doubling of Nd:YVO laser.

A stable, 22.9 W, 671 nm single-frequency laser using a type II noncritically phase-matched external-cavity frequency doubling is demonstrated. The output power of the fundamental laser is 32.

High-repetition-rate 100 W level sodium beacon laser for a multi-conjugate adaptive optics system.

A 100 W level kilohertz repetition-rate microsecond (µs)-pulse all-solid-state sodium beacon laser at 589 nm is demonstrated for the first time, to the best of our knowledge, via combining two independent µs-pulsed lasers. Each beamlet is generated by the sum-frequency mixing of pulsed 1064 and 1319 nm lasers in a lithium triborate (LBO) crystal, which operate at 500 Hz pulse repetition frequency with 61 W $p$p-polarized and 53 W $s$s-polarized output, respectively. An incoherent sequence combining technology of polarized laser beams is employed to add the two beamlets.

30 W single-frequency continuous-wave master oscillator power amplifier laser at 1342 nm.

We present a power-scalable high-power single-frequency continuous-wave 1342 nm master oscillator power amplifier (MOPA) system that consists of a polarized single-frequency 1342 nm LD seed laser, a Raman fiber preamplifier, and a three-stage ${\rm Nd}:{{\rm YVO}_4}$Nd:YVO power amplifier. The single-frequency output power of 30 W at 1342 nm is achieved with the beam quality factors ${{\rm M}^{2\:}} = {1}.{26}$M=1.

Adjustable slab-aberration compensator for high power slab laser.

An adjustable slab-aberration compensator (ASAC) with the ability to compensate the large magnitude inherent wavefront aberrations in the slab width direction is proposed and experimentally demonstrated. The ASAC has a size of 130mm×45mm (effective aperture of 75mm×28mm) and 11 actuators along the length with a contact spacing of 8 mm. The design is optimized by simulations in terms of the mirror's coupling coefficient with the contact areas, mechanical properties of the driving units, and the mirror thickness.

Void-free bonding for a large slab laser crystal.

A void-free bonding technique was demonstrated for a large slab Nd: YAG crystal with a bonding surface dimension of ∼160×70. By using the novel fluxless oxide layer removal technology, the indium-oxide barrier problem was resolved. With the help of electrochemical-polished indium solder and a plasma-cleaned heat sink, the solderability of the indium was enhanced; in particular, the contact angle of the solder was improved from 51° to 31°.

Preparation and characterization of waterborne alkyd-amino baking coatings based on waste polyethylene terephthalate.

The recycling of polyethylene terephthalate (PET) is the most attractive method for PET waste management because it not only decreases the load on landfill space, but also provides opportunities for reducing the use of raw petrochemical products. Therefore, in this investigation, neopentyl glycol is used for alcoholysis of waste PET, and glycolyzed PET product was applied for preparation of the waterborne alkyd resin. Furthermore, the waterborne alkyd-amino baking coatings were prepared from the waterborne alkyd based on glycolyzed waste PET and melamine formaldehyde resin and applied on tinplate.

24.6 kW near diffraction limit quasi-continuous-wave Nd:YAG slab laser based on a stable-unstable hybrid cavity.

A 24.6 kW quasi-continuous-wave (QCW) Nd-doped yttrium aluminum garnet (Nd:YAG) slab laser is proposed in this Letter. The laser is based on a stable-unstable hybrid cavity.

Dual-wavelength TEM mode passively mode-locked Nd:YAG laser witha semiconductor saturable absorber mirror.

A dual-wavelength ${{\rm TEM}_{01}}$TEM mode synchronous continuous wave passively mode-locked (CWML) Nd:YAG laser has been demonstrated for the first time to the best of our knowledge with a semiconductor saturable absorber mirror (SESAM) at 1319 and 1338 nm. The maximum average output power of 10.84 W was obtained at a 113.

Pulse duration adjusted by changing the cavity length with a multi-pass cavity in a Q-switched Nd:YAG laser.

We report a compact, long nanosecond (ns) pulse duration stretched laser source by a multi-pass cavity (MPC). Based on the combination of the MPC and pump power, a high-power high beam quality 1064 nm Q-switched Nd:YAG laser with a pulse duration adjustable over the range of 160-1000 ns was obtained at a pulse repetition frequency of 10 kHz for the first time, to the best of our knowledge. At a typical pulse width of 560 ns, an average output power of 10.

Watt level laser source for a polychromatic laser guide stars: double resonant fluorescence from 3S-3P-3D transition of sodium atoms.

The polychromatic laser guide star (PLGS) is one of the solutions proposed to measure the differential atmospheric tip-tilt. A watts-level microsecond pulse all solid state laser source with two wavelengths at 589 and 819.7 nm are developed to perform a proof-of-concept on-sky test for what is believed to be the first time.

Picosecond slab regenerative amplifier using a large fundamental mode stable-unstable hybrid cavity.

Slab gain media with large aspect ratios were difficult to be adopted in ultrafast regenerative amplifiers (RAs) due to the obstacle of mode matching with the seed beam. We proposed that an unstable cavity could be employed to solve this difficulty by taking the advantage of its large fundamental mode volume. In this way, an Nd:YVO slab-based picosecond RA has been successfully demonstrated using a stable-unstable hybrid cavity.

Investigation of return photons from sodium laser beacon excited by a 40-watt facility-class pulsed laser for adaptive optical telescope applications.

The brightness of the artificial beacon is one critical performance parameter for adaptive optics. Here, a 40-watt level narrow-linewidth microsecond pulsed yellow laser is produced at 589 nm with a high repetition frequency of 600 Hz and a pulse duration of 120 μs. An experiment to project the pulse beam up to the sky and measure the fluorescence photon returns of the Na atoms has been held on the 1.