Shigenori Yagi

Role of N2 gas in a transverse-flow CW CO2 laser excited by silent discharge

Experimental and theoretical investigations have been carried out on the effect of N2 gas in a transverse-flow CO2 laser excited by silent discharge (SD). It has been found that the addition of N2 is a cause of the increase of excitation efficiency compensating the effect of the increase in reduced electric field strength E/N. The excitation efficiency expressed as a function of N2 gas concentration agrees qualitatively with the results of a Boltzmann equation analysis in which the electric field is assumed to be temporally stationary and spatially uniform. The decrease in gain coefficient with N2 concentration is explained well by a model in which the stream of excited molecules due to transverse flow of gas is taken into account. The optimum gas composition for SD excitation is found to be a mixture of CO2-CO-N2-He=8-4-60-28. The optimum molar fraction of N2 is extremely high in comparison to those values reported for other types of discharge excitation.

Silent-discharge excited TEM/sub 00/ 2.5 kW CO/sub 2/ laser

The performance characteristics of the TEM/sub 00/ 2.5-kW silent-discharge-excited, transverse-flow CO/sub 2/ laser are presented. The silent-discharge excitation is advantageous for a high-quality beam pattern and for pulsed operation and sealed-off operation. Furthermore, the discharge power can be easily increased without limitation due to the instability of the discharge itself. >

Beam deflection in a transverse-flow gas laser

The beam deflection phenomenon of a transverse-flow discharge-excited CO/sub 2/ gas laser is studied by measuring the beam pattern with the rotating-wire method at gas velocities of 35-70 m/s, gas pressures of 5.3-10.6 kPa (10/sup 3/ N/m/sup 2/), and laser powers of 50-700 W. The beam deflection distance increased with increasing laser power and gas pressure and with decreasing gas velocity. All the data points of beam deflection distances observed experimentally fell on one line when normalized by the gas pressure and plotted against the measured temperature gradient in the resonator. It is shown that the most important factor affecting the beam deflection is the refractive index variation of the gas produced by the gas temperature gradient in the resonator. Methods to reduce the beam-deflection distances are suggested. >