The pulsed discharge in oxygen and its mixtures to produce singlet delta oxygen has been studied experimentally at gas
pressure of 30~ 936mBar. As singlet sigma state of oxygen O2(b1Σg+) and atomic oxygen O have great influence on the
yield of singlet delta oxygen O2(a1▵g), the visible spectrum of O2(b1Σg+) at 762nm and O at 778nm have been measured,
and the effects of argon, helium and carbon monoxide have been discussed. The electric stability was better in O2-He
than in O2-Ar mixtures, while it could be increased quickly with a small amount of CO. In O2-He mixtures more oxygen were decomposed than in O2-Ar mixtures, while adding CO the decomposition was reduced, the amount of atomic
oxygen was decreased, and the O2(b1Σg+) was increased comparatively. The time-resolved spectrum of the plasma has also been measured. The life-time of atomic oxygen was longer than O2(b1Σg+)'s, and it could be shorten with argon.
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 CO2-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 CO2-laser beam. Under these conditions, glass can
be cut with melting method without any fractures. The process of cutting glass by dual CO2-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.
We report the progress toward a novel waveguide gas laser based on hollow-core light guiding capillaries and hollowcore
photonic bandgap (PBG) fibers. Since Smith reported the first waveguide He-Ne laser at 0.633μm with a 20cm
length of 430μm-diameter-bore glass-capillary-tubing in 1971, no smaller size waveguide gas laser has ever been
constructed. Conventional hollow waveguide theory reveals that small bore size tubes suffer greater waveguide loss
which hinders the construction of smaller size waveguide gas lasers. Hollow-core PBG fibers guide light through PBG
effect that is different from grazing incidence mechanism of traditional simple hollow waveguides, and PBG fibers with
a loss of below 0.5dB/m have been demonstrated at various wavelengths including 633nm. This indicates that we may
construct waveguide gas lasers with such hollow-core PBG fibers. We carried out a series of experiments and succeeded
in discharging gases contained within 250μm, 150μm and 50μm bore diameter hollow-core light guiding capillaries or
fibers. Stable glow discharge of at least several minutes was observed for these waveguides. A flash glow was also
observed from a hollow-core capillary with a diameter of ~20μm. Initial measurements of current-voltage (I-V)
characteristics have been carried out for various tube sizes filled with various gases at different pressures. Theoretical IV
characteristics are also presented and compared with experimental results. Discharging miniature waveguide bore
tubes was found to exhibit unique characteristics that are different from the traditional larger diameter tubes.
Boltzmann equation was solved for the oxygen gas with the mixture of He, Ar, Xe etc. The electron energy distribution, electron average energy, ionization and attachment coefficient were obtained. The results have shown that the electron energy distribution over frequency is almost identical to that for the DC excitation at the same value of E/N, only in the microwave frequency range the frequency began to influence the electron energy distribution. The condition to obtain self-sustained discharge and the the influence of gas mixture on the production of singlet delta oxygen was discussed in this paper.