Lu Yuanfu

High Efficiency Multi-kW Diode-Side-Pumped Nd:YAG Laser with Reduced Thermal Effect

We demonstrate a high efficiency multi-kW diode-side-pumped Nd:YAG laser. High cooling efficiency of the diode-side-pumped module in the laser is achieved. The middle portion of the Nd:YAG rod in the module is cooled by a coolant jet with screwed side surface, and the end-caps of the rod without screwed side surface are cooled by Au coated on the surface. The thermal effect of the laser rod is reduced, which leads to high output power with high optical-optical conversion efficiency. By using three identical Nd:YAG laser modules, an output power of 4.2 kW and beam quality of 58 mm.mrad with an optical-optical efficiency of 35% at 1064 nm is obtained in a laser oscillator. By using four identical Nd:YAG laser modules, an output power of 3.1 kW and beam quality of 17 mm.mrad with an optical-optical efficiency of 25.8% is demonstrated in a master oscillator power-amplifier system.

A Continuous-Wave Diode-Side-Pumped Tm:YAG Laser with Output 51 W

A compact diode-side-pumped Tm:YAG laser is presented, which can output 51 W of cw power at 2.02μm. The Tm:YAG rod is side pumped by nine diode arrays with the central wavelength of 783nm and the with bandwidth of about 2.5 nm at 25° C. To decrease the thermal effect on the both ends and dissipate the heat effectively, one composite Tm:YAG rod with the undoped YAG end caps and the screw threads on the side surface of the rod is used as the laser crystal. The maximum optical-to-optical conversion efficiency of the 2.02-μm laser output is 14.2%, with a slope efficiency of 26.8%.

Passively Q-Switched Nd:KLuW Laser with Semiconductor Saturable Absorber

A simplified n- ZnO/ p- Si heterojunction has been prepared by growing n- type ZnO rods on p- type silicon wafer through the chemical vapour deposition method. The reflectance spectrum of the sample shows an independent absorption peak at 384 nm, which may be originated from the bound states at the junction. In the photoluminescence spectrum a new emission band is shown at 393 nm, besides the bandedge emission at 380 nm. The electroluminescence spectrum of the n- ZnO/ p- Si heterojunction shows a stable yellow luminescence band centred at 560 nm, which can be attributed to the emission from trapped states. Another kind of discrete ZnO rod has also been prepared on such silicon wafer and is encapsulated with carbonated polystyrene for electroluminescence detection. This composite structure shows a weak ultraviolet electroluminescence band at 395 nm and a yellow electroluminescence band. These data prove that surface modification which blocks the transverse movement of carriers between neighbouring nanorods plays important roles in the ultraviolet emission of ZnO nanorods. These findings are vital for future display device design.

High power high beam quality diode-pumped 1319-nm Nd:YAG oscillator-amplifier laser system

This paper demonstrated a high power and high beam quality diode-pumped 1319-nm Nd:YAG master oscillator-power amplifier laser system. A thermally near-unstable resonator with four-rod birefringence compensation flat-flat cavity was adopted as the master oscillator. A solid etalon was inserted in the unidirectional ring resonator to compress the laser linewidth. Under a repetition rate of 500 Hz and pulse width of 160 μs, the master oscillator delivers an average output power of 16.8 W at 1319 nm with linear polarisation, beam quality factor M2 = 1.16 and linewidth of 3.2 GHz. A double-pass power amplifier with two amplifier stages was employed for higher power scaling and the output power was amplified to be 25.9 W with M2 = 1.43.

Tunable and narrow linewidth yellow beam generation by sum-frequency mixing of diode-pumped Nd:YAG ring lasers

Output power of 1.1 W and linewidth of 0.7 GHz and beam quality of M2 = 1.2 yellow beam was generated by sum-frequency mixing 1064 nm and 1319 nm radiations of quasi-continuous-wave diode-pumped Nd:YAG lasers inside a pair of KTP crystals. The narrow linewidth 1064 nm and 1319 nm beams were realized by inserting solid etalons in the three-mirrors ring resonators. The wavelength of yellow laser was adjusted and controlled by the control of etalon angle and temperature. To achieve the high beam quality at the average power, thermally near-unstable resonators with two-rod birefringence compensation were designed and employed in the 1064 nm and 1319 nm ring lasers. The high sum-frequency efficiency was obtained by using a pair of KTP crystals with a walk-off-compensated configuration. The power of the diffraction-limited, narrow linewidth and precise-tunability yellow laser was reached to 1.1 W by mixing the 1064 nm beam of 7.5 W and the 1319 nm beam of 3.2 W.

Highly Efficient Diode-Side-Pumped Six-Rod Nd:YAG Laser

We have demonstrated a highly efficient, high average output power laser based on the optimized resonator made up of multiple Nd:YAG rods. The laser consists of three groups, each of which contains two rods with one quartz 90° rotator between them. By a desirable design of the resonator, the average output power of 1906 W at 1064 nm is reached with repetition rate of 1.1 kHz. The optical to optical conversion efficiency is up to 50.8% with the pulse width 224 μs and it is the highest conversion efficiency of six rods resonator.

A 4.8-W M-2=4.6 continuous-wave intracavity sum-frequency diode-pumped solid-state yellow laser

A yellow continuous wave with beam quality M-2 = 4.6 and output power of 4.8 W at 589 nm is generated by intracavity sum-frequency mixing of 1064 nm and 1319 nm radiations of ND:YAG laser. To achieve high beam quality at high power, thermally near-unstable flat-flat resonators with two-rod birefringence compensation are designed to obtain the large fundamental mode size inside the ND:YAG rods and the same beam width inside the KTP crystal. The optimal intracavity power ratio of both 1064 nm and 1319 nm beams is also considered. The output power fluctuation of the yellow laser remains less than 5% in four hours.

An optical system in solar-blind UV for corona discharge detection

A bi-spectral camera for visible and solar-blind UV (240nm-280nm) was developed for detecting the corona discharge. Due to the UV light generated by corona discharge is very weak, so an optical system by careful calculation was designed for the UV band. The UV optical system was schemed with the focal length of 200mm, relative aperture of 1:2.77 and the FOV of ±2°. The assembly of UV optical system also introduced in paper. A new method used to solve the problem of corona point not calibration in non-central of FOV in fusion image. After calibrating, the position of corona discharge can be observed accurately by overlaying UV image of the corona on a visible light image of the background. The bi-spectral optical system was accomplished and tested in the lab. Results showed that the FOVs of visible light and solar-blind UV optical systems were matched well.

A 1550-nm linearly tunable continuous wave single-mode external cavity diode laser based on a single-cavity all-dielectric thin-film Fabry—Pérot filter

A 1550-nm linearly tunable continuous wave (CW) single-mode external cavity diode laser (ECDL) based on a single-cavity all-dielectric thin-film Fabry—Perot filter (s-AFPF) is proposed and realized in this paper. Its internal optical components as well as their operation mechanisms are introduced first, and then its longitudinal mode output characteristic is theoretically analyzed. Afterwards, we set up the experimental platform for the output characteristic measurement of this tunable ECDL; under different experimental conditions, we execute accurate and real-time measurements for the output central wavelength, output optical power, output longitudinal mode distribution, and the line-width of the tunable ECDL in its tuning process. By summing up the optimal experimental condition from the measured data, we obtain the optimal tunable ECDL relevant parameters: the tunable ECDL has a linear mode-hop-free wavelength tuning region of 1547.203 nm–1552.426 nm, a stable output optical power in the range of 40 μW–50 μW, and a stable output longitudinal mode distribution of a single longitudinal mode with a line-width in the range of 100 MHz–150 MHz. This tunable ECDL can be used in environmental gas monitoring, atomic and molecular laser spectroscopy research, precise measurements, and so on.

218 W,M 2 = 20.2 green beam generation by intracavity-frequency-doubled diode-pumped Nd:YAG laser

By employing a thermally near-unstable cavity design with two-rod birefringence compensation, average power of 218 W with beam quality of M2 = 20.2 was achieved by intracavity frequency doubling a diode-pumped Nd:YAG laser.