Planar and cylindrical surface corona discharge TEA $CO_2$ laser systems are designed and fabricated. Their output energies are investigated and compare with that of triple discharge TEA $CO_2$ laser. These types are superior to the triple discharge type in output energy and stability in laser operation. The maximum output energies of these types are about 4.5 times and 3.5 times, respectively, to that of the triple discharge type.
The active acousto-optic mode locking experiment is carried out for TEA $CO_2$ laser. The acousto-optic modulator consists of a diffraction cell and a transducer. The diffraction cell is made of a GaAs single crystal with the dimensions of 1.2cm × 2cm × 1.4cm. The X-cut quartz transducer (resonant frequency: 28.86 MHz) is driven by an amplified RF signal. The modulation depth of TEA $CO_2$ laser pulse becomes deeper as the RF power increases. An output pulse train with 16.7ns time interval is obtained and the width of the pulse at the center is about 2.67 ns at half intensity.
The self-focusing and self-defocusing of TEA-$CO_2$ laser beam in far infrared laser media is investigated. FIR laser media, such as, $CH_3I$, $NH_3$, $CF_4$, HCOOH, $CH_3F$, $CH_3OH$ and $C_2H_5OH$ are used. The $NH_3$ and $CH_3F$ media have the self-focusing or/and self-defocusing effects, and $CH_3I$, $CF_4$, $CH_3OH$, $C_2H_5OH$, HCOOH media do not show explicit self-focusing or self-defocusing for all TEA-$CO_2$ laser lines. The positive and negative nonlinear refractive index coefficients of $NH_3$ and $CH_3F$ molecules are determined for TEA-$CO_2$ laser lines by observing the far field spatial distortions of the output gaussian beam passing through the nonlinear cell.