Wei Zhiyi

Laser Performance of Nd:GGG Operating at 938 nm

We report an efficient diode-pumped Nd-doped Gadolinium gallium garnet (GGG) continuous-wave (CW) laser operating at 938 nm. Laser action of 1.6at.% Nd-doped GGG crystals with different lengths and temperatures are also investigated. The maximum output power of 620 mW is obtained at the incident pump power of 5.0 W with a slope efficiency of 15%.

Diode-pumped passive Q-switched 946-nm Nd : YAG laser with 2.1-W average output power

We demonstrate a diode-pumped passive Q-switched 946 nm Nd:YAG laser with a diffusion-bonded composite laser rod and a co-doped Nd,Cr:YAG as saturable absorber. The average output power of 2.1 W is generated at an incident pump power of 14.3 W. The peak power of the Q-switched pulse is 643 W with 80 kHz repetition rate and 40.8 ns pulse width. The slope efficiency and optical conversion efficiency are 17.6% and 14.7%, respectively.

The characteristics of confined ablation in laser propulsion

Compared with direct ablation, confined ablation provides an effective way to obtain a large target momentum and a high coupling coefficient. By using a transparent glass layer to cover the target surface, the coupling coefficient is enhanced by an order of magnitude. With the increase of the gap width between the target surface and the cover layer, the coupling coefficient exponentially decreases. It is found that the coupling coefficient is also related to the thickness of the cover layer.

Generation of Sub-2 Cycle Optical Pulses with a Differentially Pumped Hollow Fiber

We report the generation of optical pulses with an energy of 0.55 m J and duration of 1.6-cycle (4.4 fs) at repetition rate of 1 kHz using a differentially pumped hollow fiber and chirped mirrors. Compared to the statically gasfilled scheme, the differentially pumping hollow fiber is demonstrated to support more energy output with higher transmission efficiency, and to increase the spectral broadening due to a reduction of ionization defocusing in plasma at the fiber entrance. The differentially pumping technique is proved to be an effective way to obtain optical pulses with mono-cycle and higher energy.

Efficient Tm:YAG Ceramic Laser at 2 μm

We demonstrate a high-efficiency continuous-wave Tm:YAG ceramic laser pumped with a Ti:sapphire laser. An output power up to 860 mW is obtained under an absorbed pump power of 2.21 W at 785nm, corresponding to a slope efficiency of 42.1% and optical to optical efficiency of 22%. The measured central wavelength is 2012 nm.

Compact diode-pumped continuous-wave Nd : LuVO4 lasers operated at 916 nm and 458 nm

We report the compact diode-pumped continuous-wave (CW) Nd:LuVO4 lasers operated at 916 nm and 458 nm for the first time. The maximum output power of 780 mW at 916 nm laser is obtained with a slope efficiency of 9.3%. We generate 50 mW of 458 nm blue laser employing a type-I critical phase-matched LBO crystal.

Effects of Confined Laser Ablation on Laser Plasma Propulsion

We investigate the effects of confined laser ablation on laser plasma propulsion. Compared with planar ablation, the cavity ablation provides an effective way to obtain a large target momentum and a high coupling coefficient. When laser pulses are focused into a cavity with 1 mm diameter and 2 mm depth, a high coupling coefficient is obtained. By using a glass layer to cover the cavity, the coupling coefficient is enhanced by 10 times. Meanwhile, it is found that with the increase of the target surface size, the target momentum presents a linear increase.

Diode-Pumped Self-Starting Mode-Locked Nd:YVO4 Laser with Semiconductor Saturable Absorber Output Coupler

By using a semiconductor saturable-absorber output coupler as a mode-locking device, we experimentally realized the operation of a diode-pumped passively mode-locked Nd:YVO4 laser. Stable laser pulses with duration of 2.3 ps were generated at the output power of about 1 W. With increasing the pump power to 9 W, the maximum mode-locked power of 1.7 W was obtained, which corresponds to a slope conversion efficiency of 44% and optical-to-optical conversion efficiency of 19%.

Generation and Measurement of Isolated 160-Attosecond XUV Laser Pulses at 82 eV

Isolated attosecond extreme-ultraviolate (XUV) pulses are generated based on high-harmonic-generation from a neon gas cell driven by carrier-envelope phase stabilized sub-5-fs Ti:sapphire laser pulses at repetition rate of 1 kHz. Temporal characterization of isolated attosecond XUV pulses is demonstrated to be 160-attosecond by attosecond streaking spectroscopy. The development of attosecond source and streaking spectroscopy will allow scientists to explore the electron dynamics in matter.

Generation of 170-fs Laser Pulses at 1053 nm by a Passively Mode-Locked Yb:YAG Laser

A novel method is developed to obtain 1.05 μm laser operation with a Yb:YAG laser. By using a Yb:YAG crystal with proper length and doping concentration, a femtosecond Yb:YAG laser is realized at the central wavelength of 1053 nm. The measured pulse duration and spectral bandwidth (FWHM) are 170 fs and 7 nm; the repetition rate is 80 MHz. Under a power pump of 2 W, an average mode-locking power of 180 mW is achieved.