Optimization of tunable CO2 laser outputs by automated setting of intra-cavity emission polarization for each line

The present paper is concerned with automatic optimization of tunable CO2 laser emission power that has been realized by changing the in-resonator polarization direction. We have begun with the investigation into the experimental reflection efficiency of the grating in use for first and zero diffraction orders as a function of the incident polarization plane orientation relative to the grating line length obtained from the first-order Littrow system. The dependencies measured were then used to determined the angle gamma (J) between the grating line length and the polarization vector such that the zero-order reflection factor was equal to its optimal value that is a function of the active medium gain for the J-th line, active length, and useless loss inside the laser cavity. After this, the monitoring and control software of the laser has been enhanced with the gamma (J)-values found out in accordance with the above procedure for each laser line associated with its intrinsic gain. Hence, the laser tuning in J-th line is accompanied with automatic orientation of the Brewster window at the angle gamma (J). Due to the given optimization we were able to acquire for each particular line the highest power at the maximum line amount in the output spectrum.