Abstract
The computer-aided design of high quality mono-mode, continuous-wave solid-state lasers requires fast, flexible and accurate simulation algorithms. Therefore in this work a model for the calculation of the transversal dominant mode structure is introduced. It is based on the generalization of the scalar Fox and Li algorithm to a fully-vectorial light representation. To provide a flexible modeling concept of different resonator geometries containing various optical elements, rigorous and approximative solutions of Maxwell's equations are combined in different subdomains of the resonator. This approach allows the simulation of plenty of different passive intracavity components as well as active media. For the numerically efficient simulation of nonlinear gain, thermal lensing and stress-induced birefringence effects in solid-state active crystals a semi-analytical vectorial beam propagation method is discussed in detail. As a numerical example the beam quality and output power of a flash-lamp-pumped Nd:YAG laser are improved. To that end we compensate the influence of stress-induced birefringence and thermal lensing by an aspherical mirror and a 90° quartz polarization rotator.
Highlights
For the numerically efficient simulation of nonlinear gain, thermal lensing and stress-induced birefringence effects in solid-state active crystals a semi-analytical vectorial beam propagation method is discussed in detail
For the calculation of the laser beam power the Gaussian beam propagation technique is combined with a semi-classical separation approach [2,19,20,21,22], meaning that the laser beam power is separately calculated from the transversal mode structure by rate equations and an integration of the photon density over the resonator volume. This separation results in approximations which are not fulfilled in all laser resonators, e.g. the effects on the beam profile caused by nonlinear gain saturation as well as diffraction losses caused by intracavity apertures are neglected
We will apply the model in a numerical example, showing how the resonator geometry and the application of intracavity components can decrease the negative effects of stress-induced birefringence and thermal-lensing on the beam quality and output power of the dominant laser resonator mode
Summary
The computer-aided analysis and optimization of the beam quality and power of mono-mode, continuous-wave (cw) laser sources is of increasing importance to reduce development cycle times and costs of high performance lasers. Methods based on the Gaussian beam propagation technique [14, 15], which are sometimes called ABCD-Matrix approaches, are restricted in their applicability to paraxial resonator setups containing passive intracavity components introducing quadratic phase terms, like paraxial, thin lenses. These approximated techniques only include physical effects of simplified active components. We will apply the model in a numerical example, showing how the resonator geometry and the application of intracavity components can decrease the negative effects of stress-induced birefringence and thermal-lensing on the beam quality and output power of the dominant laser resonator mode
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