| Abstract [eng] |
Synchronously Pumped Optical Parametric Oscillator Beam Quality Analysis Beam quality is one of the most important laser parameters. Optical parametric oscillators (OPOs) are not an exeption and it is necessary to try to get the beam quality as close to the fundamental Gaussian mode as possible. Contemporary scientific and industrial applications of the OPO‘s require good beam quality therefore it is necessary to investigate the underlying principles that determines it. The experiments were carried out on a measurement system consisting of an OPO and an external telescope (so that it would be possible to change signal and pump beam diameters). Beam quality parameters were measured under several different signal and pump beam widths. „reZonator“ software was used to simulate the propagation and to determine signal and pump beam widths. Additionally an asymetry module for the pump beam was incorporated to the measurement system. Beam quality parameters were measured when the system was pumped with a symetric and with an asymetric pump beam. Furthermore, beam quality of the OPO was measured under different nonlinear crystal and pump beam waist positions in the OPO cavity. Finally, asymmetry was added to the signal beam. OPO beam parameters were measured depending on nonlinear crystal position in the resonator, resonator stability parameters, pump beam focus position and pump power. From the collected data it was possible to determine beam quality regions of the OPO, depending on pump and signal beam diameters. It is also shown that beam properties of an OPO signal wave do not depend on the asymmetry of the pump beam, with the amount of asymmetry that was implied in the system. OPO output power, astigmatism, asymmetry and M2 relationships to nonlinear crystal position and pump beam waist position are presented in this work. It is shown that astigmatism is dependant on the signal mode beam diameter in the nonlinear crystal, asymmetry can be controled with an additional asymmetry module in the resonator and that asymmetry and astigmatism are dependant on pump power, due to the Kerr lens effect. |
