Xisheng Ye

Discharge pumped non-chain repetitively pulsed HF laser

The design and performance of a closed cycle, repetitively pulsed HF laser is described. The homogeneous glow discharge is formed with UV pre-ionization and transverse discharge structure. The optimal output parameters of single pulse operation are given by the investigation of discharge characteristics in SF6 /C2H6 gas mixture and output characteristics of laser pulse. The repetitively pulse energy stability of laser device are checked with different conditions of gas flowing velocity, charging voltage and total pressure of gas mixture. It is shown that the maximal output energy of laser pulse of 0.6J, peak power 3MW are obtained. Total efficiency of laser device is about 2.4%. When the gas mixture circulating with 4m/s flowing velocity, the maximal running frequency of 50Hz are obtained and operating stability keep well. Under these conditions, the laser pulse energy keeps stable and the average output power is 18W.

The research on the technology of surface discharge optical pumping source

This paper describes systematically the properties of the surface discharge pumping source. The pre-ionization technology was investigated. The characteristics of the surface discharge and the photodissociation wave of exciting media have been studied. The temporal and Spatial Stability of discharge were measured and analyzed. The discharge spectral and ablation rate of three different materials were obtained.

Discharge initiated high power repetitively pulsed HF/DF laser

The design and performance of a closed cycle, repetitively pulsed HF/DF laser is described. For obtained higher stable laser pulse energy and running frequency, discharge stability with different electrode profile and different gas circulation structure are researched. The functional relations of laser pulse energy with electric field strength (E) and gas mixture pressure (P) for various gas flow velocity are studied. It is shown that with preliminary optimized of the gas injection segment structure before pump region and optimal E/P conditions, maximal running frequency of 100Hz is obtained and operating stability keeps well. Under these conditions, the laser average power is 40W and peak power is 4MW.

Development of optically pumped XeF laser technology in NINT

The investigations of the XeF laser bumped by ultraviolet radiation have been studied for more than 20 years in Northwest Institute of Nuclear Technology (NINT Xi’an China). Up to now, several XeF laser devices were developed and an integrative experimental system has been set up which is comprised of a laser device, an electrical power supply, a high voltage trigger generator and a mixture gas supply device. Many key technologies were studied in detail and have been applied now. These technologies include section surface discharge, XeF2 photodissociation, synchronal trigger generating, double-sides optical pumping from opposite directions, active mixture gases supplying in real time, gases circulation, and so on. The XeF laser system operating on pulse repetition frequency (PRF) is up to 10 Hz. Two kinds of operating modes were applied. For the open gas flowing mode, the pulse energy of 3.2 J and the average power of 32 W at 10Hz is obtained. For the gases circumrotate mode, the average energy of 20 laser pulses is more than 0.5J.

Gain-switched 2.8μm Er3+-doped double-clad ZBLAN fiber laser

A pulsed Er3+-doped ZBLAN fiber laser at 2.8 μm in fundamental-transverse-mode operation is reported. Stable gainswitching is achieved with the repetition rate range from 0.5 to 10 kHz. The maximum laser pulse energy of up to 4.2 μJ and pulse duration of 1.18 μs at a repetition rate of 10 kHz, yielding the maximum peak power of 3.5 W, has been obtained. The maximum slope efficiency with respect to the launched pump power at 975 nm is determined to be 12.2%. Pulse spikes occur by increasing the pump energy of larger than 75 μJ.

Experimental study on output energy stability of discharge-initiated repetition rate HF laser

The output energy stability of discharged-pumped pulsed HF laser in repetition rate mode is studied experimentally, and the optimal operating conditions are obtained. The experimental results show that the output energy decreases quickly with the increase of repetition rate, and increasing gas flow rate is beneficial to improve the discharge stability and the output energy stability as well. By optimizing the operating conditions, the laser can operate stably at the repetition rate of 50 Hz, with the stable output energy of about 260 mJ, and the average power is about 13 W.

Study on the technology of the high power XeF(C-A) laser with repetition mode

This paper presents the results of studies on high power photochemical XeF(C-A) laser with repetition mode. A new design of optical pumping source is proposed and the deposition efficiency is higher than 75 %. The form process and the temporal and spatial characteristics of the XeF2 photodissociation wave are studied experimentally. The results indicate that when the deposition power is 12.5 MW/cm, the maximum brightness temperature reaches more than 25 kK and the photon flux obtained more than 4×1023 photon s-1 cm-2 in the VUV range of 130 nm~180 nm. A novel XeF(C-A) laser which can be operated in repetition mode has been developed based on surface discharge optical pumping technique. The ideal output energy results of 20 laser pulses are presented under different repetitive rates and their optimal experimental conditions. Output energies of more than 4J and better stability can be obtained when the laser device operates at 1, 2 and 5 Hz, respectively. When the gas feed rate is larger than 53L/s, the average energy of 20 laser pulses is up to 3.2J at the repetitive rate of 10Hz. The technology for the laser spectral narrowing is studied.

Research on quasi-phase-matched mid-infrared optical parametric oscillator

The theoretical analysis and experimental research of the optical parametric oscillator (OPO) based on periodically poled LiNbO3 (PPLN) crystal are presented. The wavelength tuning curves of PPLN-OPO are calculated through the coupling equations of the three-wave mixing. An optical parametric oscillator with the output signal at 1.49μm and idler at 3.8μm, which is pumped by a Nd:YAG laser at 1.064μm, is obtained based on PPLN of length 20mm and thickness 0.5mm. When the pump power of the Nd:YAG laser is 5.2W with a repetition rate of 5kHz, the output of the idler at 3.8μm reaches 307mW.

Generation of strongly coupled plasmas by high power excimer laser

(ultraviolet). To generate strongly coupled plasmas (SCP) by high power excimer laser, an Au-CH-Al-CH target is used to make the Al sample reach the state of SCP, in which the Au layer transforms laser energy to X-ray that heating the sample by volume and the CH layers provides necessary constraints. With aid of the MULTI-1D code, we calculate the state of the Al sample and its relationship with peak intensity, width and wavelength of laser pulses. The calculated results suggest that an excimer laser with peak intensity of the magnitude of 1013W/cm2 and pulse width being 5ns - 10ns is suitable to generate SCP with the temperature being tens of eV and the density of electron being of the order of 1022/cm-3. Lasers with shorter wavelength, such as KrF laser, are preferable.

The development of XeF(C-A) lasers by optical pumping

The development of XeF(C-A) lasers by optical pumping in Northwest Institute of Nuclear Technology during recent 10 years is described in this paper. A joule level of XeF(C-A) laser optically pumped by a sectioned surface discharge was studied with the total efficiency of 0.1%. A more efficient XeF(C-A) laser was developed with the maximum outpup energy of 18.6 joules by two-side optically pumping and repetition mode operating.