A study on the design of CW Er:YAG laser

This thesis gives a design of CW Er:YAG laser with output power of (10-90 W) at 2.94 μm wavelength which has been used in medical applications for its strong absorption in waters other than CO2 laser. A beam transform system has been algorithmly designed by visual basic and used for focusing the diode laser beam inside the active medium with (0.4mm) spot size and reshaping the high elliptically beam profile to a circular shape by using identical prism pair with a magnification factor x4 and total beam transitions of 78% . A theoretical analysis has been made of the thermal effects of high power end-pumped Er:YAG laser, and their influence on the laser output characteristics, particularly the beam quality.The theory of thermal lensing and stress-induced birefringence for the case of Gaussian laser modes has been theoretically studied and modeled. The reduction of the birefringence loss was achieved by inserting quarter wave plates between the laser rod and the laser end mirror. An analysis is given of the tolerance of laser resonators to thermal lensing, providing guidelines for the choice of resonator parameters in order to ensure sufficient resonator stability margins.The results of numerical simulations of an end pumped Er: YAG laser are given. It is found that the analytic theory provides fairly good guidelines concerning the choice of resonator parameters in many cases. It is found that the optimal choice of resonator parameters is when a (50W) pump power beam is converted to (10 W) output power at (2.94μm) wavelength, with a laser beam
quality of M2 < 2.