The evolution of shock wave generated by discharge in laser chamber is one of the key factors which affect laser beam
quality, discharge stability, and repetition rate of TEA gas laser. In this paper, Mach-Zehnder interferometer is applied to
observe both the longitudinal and transversal shock waves between electrodes as well as the acoustic waves originated
by preionization in the discharge pumping zone of TEA gas laser. By changing the discharge voltage, gas pressure and
gas composition concentration, the developing processes in different conditions are compared and analyzed. It is
observed that the shock waves originating from cathode is different from the anode's ones even in the symmetric
electrode construction. And the carbon dioxide concentration in helium-buffered working gas can affect the speed of the
wave obviously. However, the increasing trend of shock wave speed, when increasing discharge voltage or reducing
discharge gas pressure, is inconspicuous.
The efficiency of a simply designed optically pumped terahertz laser is studied experimentally. The terahertz laser cavity
only consists of a quartz glass tube, an antireflection-coated Ge window and a SiO<sub>2</sub> window. The Ge crystal acts as the
high-reflectivity mirror of terahertz radiation and the input coupler of pump laser instead of complicated metal-mesh
mirrors. The Ge crystal is near 3 mm thick, whose exact thickness is designed according to etalon effects to maximize
terahertz reflectivity. NH3 gas is filled in the cavity as the active medium and pumped by a TEA CO<sub>2</sub> laser. As high as
25.9 mJ terahertz radiation at the wavelength of 151.5 μm is extracted from 1.76 J pump energy. The corresponding
photon conversion efficiency of this terahertz laser reaches 41.5%. A 4.7-mm-thick GaAs crystal and a 6-mm-thick ZnSe
crystal are also chosen to be the input coupler. The experimental results show that the efficiency of the Ge window is
54% and 66% higher than that of the GaAs and ZnSe windows, respectively. The reason of the higher efficiency of the
Ge window is demonstrated experimentally and theoretically in this paper.
The studies on a short pulsed TEA (Transversely Excited Atmospheric pressure) CO<sub>2</sub> laser pumped by a magnetic pulse
exciter are reported. The exciter includes a magnetic pulse compression circuit, which compresses the pulse duration
below 100 ns. According to our experiments, the maximum output energy of a single pulse can be as high as 2.84 J and
the Full Width at Half Maximum (FWHM) of the laser pulse is 70ns approximately. The pulse shapes and characteristic
times are measured. The results indicate that the single pulse energy keeps a linear relation with the gas pressure and
charge voltage. And there is an optimized composition that the maximum output pulse energy or shortest pulse width can
be obtained. Based on this free oscillation laser, a tunable TEA CO<sub>2</sub> laser is developed. Over 62 laser lines from 9.16 to
10.79μm have been obtained and the output pulse energy of 10P(20) line is 0.5 J.
A theoretical model is established to describe the α-RF discharge in slab Oxygen Iodine lasers, according to the
continuity equation of electron density, the electron energy equilibrium equation and the continuity equation of current
density. Assuming a Maxwellian energy distribution, the spatial distributions of electron density and electric field in RF
plasma are obtained by numerical method. The effects of parameters on discharge characteristics have been analyzed.
The results show that the current density has a big effect on the electron density in discharge area. The influences of
excitation frequency on the maximum value of electric field and the thickness of boundary layer are also discussed. And
the spatial distributions of electron energy and excitation efficiency of singlet delta oxygen have been calculated. The
influences of gas mixture on the excitation efficiency of singlet delta oxygen are discussed. It provides references of
parameters for slab discharge in singlet delta oxygen generating.
Cutting brittle materials such as ceramics and glass by lasers or traditional saw method, costly fractures and associated
damage such as chips and cracks can result. In most cases, these problems were caused as a result of the stress was not
controlled properly and exceeded the critical value of the fracture. In this study, a dual-laser-beam method was proposed
to avoid fractures in glass laser cutting, where an off-focused CO<sub>2</sub>-laser beam was scanning on the top surface of glass
periodically and repeatedly and a preheated-band which has a proper temperature was built. This preheated-band will
reduce the temperature gradients when the glass is cut by the focused CO<sub>2</sub>-laser beam. Under these conditions, glass can
be cut with melting method without any fractures. The process of cutting glass by dual CO<sub>2</sub>-laser beams was simulated
numerically with FEA method and the distribution of temperature and thermal stress was investigated. The relationships
between the cutting parameters, such as laser beam diameter, laser power, cutting speed, and the profile of the cutting
groove were also discussed. The result showed that thermal stress decreased with the increasing width of
preheated-banding, and the smaller the diameter of laser beam, the better the quality of the cutting groove was in the
same laser power situation.