Advanced Solid-State Photonics 2009

Short course SC332, Sunday, February 1, 2009, 2:00 to 6:00 PM

How to Use Software LASCAD for LASer Cavity Analysis and Design

Konrad Altmann, LAS-CAD GmbH, Germany

Course Description

Modern SSL performance is affected by a diversity of materials, pump and cavity configurations causing complicated 3D interaction of strong fields in tiny crystal volumes.

This course explains how to model SSL, using LASCAD software. Four interactive software tools enable users to do:

1) geometrical ABCD matrix mode analysis, 2) finite element analysis (FEA) of thermal and mechanical effects, 3) dynamic analysis of gaussian multimode and Q-switch operation, and 4) physical optics analysis (BPM).

It is shown how temperature distribution, thermal deformation and stress in the crystal can be computed using FEA. By the use of this tool it is demonstrated how different configurations, materials, and doping, affect temperature and crystal deformation.

FEA results can be combined with a gaussian mode approximation. For this purpose the thermally induced modification of the refractive index is fitted parabolically transverse to the crystal axis. The obtained parabolic parameters are used in an ABCD matrix code, which immediately delivers the shape of the transverse gaussian modes.

In a next step, the obtained gaussian modes are used to carry through a dynamic analysis of multimode and Q-switch operation, by solving the time dependent rate equations for a set of transverse modes, again using an FEA solver on a space-time domain. This delivers the contribution of the individual modes to power output, beam quality factor, and pulse shape.

Alternatively, the results of FEA can be used with a physical optics code propagating a wavefront through the obtained 3D data set using a split-step beam propagation method.

Benefits and Learning Objectives

This course should enable participants to

Model resonator mode structure using ABCD matrix gaussian mode approximation.
Carry through finite element analysis of heat conduction and thermal deformation.
Model common laser configurations like end and side pumped systems.
Demonstrate the effects of different pumping and doping on mode structure, laser efficiency, and beam quality.
Compute the power output for 4-level and quasi 3-level laser systems.
Model the effect of pump light and temperature distribution on quasi 3-level-and 4-level-laser systems.
Carry through dynamic modeling of multimode and Q-switch operation.
Use a split-step BPM code to analyze a laser resonator applying the Fox and Li type roundtrip algorithm.

Course Level

Advanced beginner (basic understanding of topic is necessary to follow course material)

Intended Audience

This course is intended for individuals with at least a basic knowledge of lasers. Students, laser engineers and scientists, interested in using modeling software for laser design and educational purposes, are welcome.

Instructor Biography

Konrad Altmann is president of LAS-CAD GmbH, Munich, Germany. He received diploma and doctorate degree from University of Munich. Working in defense industry he developed modeling software for high energy lasers, and laser beam propagation in the atmosphere. In 1993 he founded LAS-CAD GmbH with the vision of providing laser engineers all the simulation tools necessary for a quantitative understanding of the complicated multiphysics interaction in solid state lasers. In 2000 LAS-CAD received the Laser Focus World Commercial Technology Achievement Award.