The second fusion of laser and aerospace-an inspiration for high energy lasers

Since the first laser was invented,the pursuit of high-energy lasers(HELs)has always been enthusiastic.The first revolution of HELs was pushed by the fusion of laser and aerospace in the 1960s,with the chemical rocket engines giving fresh impetus to the birth of gas flow and chemical lasers,which finally turned megawatt lasers from dream into reality.Nowadays,the development of HELs has entered the age of electricity as well as the rocket engines.The properties of current electric rocket engines are highly consistent with HELs’goals,including electrical driving,effective heat dissipation,little medium consumption and extremely light weight and size,which inspired a second fusion of laser and aerospace and motivated the exploration for potential HELs.As an exploratory attempt,a new configuration of diode pumped metastable rare gas laser was demonstrated,with the gain generator resembling an electric rocket-engine for improved power scaling ability.

A Simplified Numerical Study of the Kr/Cl_2 Plasma Chemistry in Dielectric Barrier Discharge

In this paper, the generation of excimers and exciplexe radiation in mixtures of rare gas with halogen by homogeneous dielectric barrier discharge （DBD） is investigated. The typical characteristics of an excilamp based on KrCI＊ exciplexe molecules and the kinetic processes for the formation and the decay of this molecules in the Kr/Cl2 mixture are studied. The computer model developed is based on the Kr/Cl2 mixture chemistry, the equivalent electric circuit and the Boltzmann equations. The importance in the kinetic processes of some species such as the metastable state of Krypton （Kr＊（3P0,2）） and the negative ion of chloride （C1-） is considered. The results illustrate the time variations of charged species （ne, Kr＋, CI-, Cl＋, Cl＋, Kr＋）, excited atoms and molecules （Kr＊（3p0,2）, Kr＊（3P1）, Cl＊, Cl2）, the excimers （Kr, KrCl＊（B）, KrCI＊（C）, Kr2Cl＊） and the UV photon concentrations （in 222 nm, 235 nm, 258 nm and 325 nm range）. The effects of chlorine concentration and the total gas pressure in the Kr-Cl2 discharge on the electric parameters and radiation emissions are investigated.

Nanocrystalline Gd_(1–x)Ca_xFeO_3 sensors for detection of methanol gas

The sol-gel method was used to prepare the nanocrystalline Gd_（1–x）Ca_xFeO_3 （x=0–0.4） powders. The XRD results showed that all the Gd_（1–x）Ca_xFeO_3 （x=0–0.4） compounds crystallized as perovskite phase with orthorhombic structure. The doping of Ca in GdFeO_3 not only reduced the resistance, but also enhanced the response to methanol. The Gd_（0.9）Ca_（0.1）FeO_3 showed the best response to methanol among Gd_（1–x）Ca_xFeO_3 sensors. Besides, it showed good selectivity to methanol among methanol, ethanol, CO and formaldehyde gases. The responses at 260 oC for Gd_（0.9）Ca_（0.1）FeO_3-based sensor to 600 ppm methanol, ethanol and CO gases were 117.7, 72.7 and 31.9, respectively. Even at quite low gas concentrations, Gd_（0.9）Ca_（0.1）FeO_3-based sensor had an obvious response. At 260 °C, the response of 1.54 was obtained to be 45 ppm methanol. The experimental results showed that nanocrystalline Gd_（0.9）Ca_（0.1）FeO_3 based sensor can be used to detect methanol gas.

Demonstration of a diode-pumped dual-wavelength metastable krypton laser

Diode-pumped rare gas lasers are potential candidates for high-energy and high-beam quality laser systems.Currently,most investigations are focused on metastable Ar lasers.The Kr system has the unique advantages of higher quantum efficiency and lower discharge requirements for comparison.In this paper,a diode-pumped metastable Kr laser was demonstrated for the first time.Using a repetitively pulsed discharge at a Kr/He pressure of up to approximately1500 Torr,metastable Kr atoms of more than 10^(13)cm^(-3)were generated.Under diode pumping,the laser realized a dual-wavelength output with an average output power of approximately 100 mW and an optical conversion efficiency of approximately 10% with respect to the absorbed pump power.A kinetics study involving population distribution and evolution was conducted to analyze the laser performance.

Segmented pulsed discharge for metastable argon lasing medium

Direct current pulsed discharge is a promising route for producing high-density metastable particles required for optically pumped rare gas lasers(OPRGLs).Such metastable densities are easily realized in small discharge volumes at near atmospheric pressures,but problems appear when one is trying to achieve a large volume of plasma for high-power output.In this work,we examined the volume scalability of high-density metastable argon atoms by segmented discharge configuration.Two discharge zones attached with peaking capacitors were connected parallelly by thin wires,through which the peaking capacitors were charged and of which the inductance functioned as ballasting impendence to prevent discharging in only one zone.A uniform and dense plasma with the peak value of the number densities of Ar(1s^(5))on the order of 10^(13)cm^(-3)was readily achieved.The results demonstrated the feasibility of using segmented discharge for 0PRGL development.