The complex behavior of the optical wave in laser resonators requires a comprehensive model of thermal lensing
and the dynamic, 3-dimensional behavior of the laser beam. To this end, we perform a combined finite element
analysis (FEA) of the optical wave and of thermal lensing. Here, the simulation of the optical wave is the most
challenging task. Therefore, we also discuss another method, Dynamic Multimode Analysis, which is suitable
for a wide range of lasers. Finally, we present a complex heat model in order to analyze the interaction of heat
generation, thermal lensing, laser dynamics, and the beam profile.
KEYWORDS: Interfaces, Resonators, Crystals, Laser resonators, Optical simulations, Mirrors, Solid state lasers, Computer simulations, Finite element methods, Chemical elements
The complex physical optics behavior in modern solid state lasers can only approximately be described using
common simulation techniques, such as a Gaussian mode analysis or beam propagation methods. For this reason
we present a new 3-dimensional, time-dependent method to model the laser beam in a resonator in a more
comprehensive way. We transform the wave equation by a special ansatz and solve the resulting equation, which
is similar to a Schroedinger equation, by a finite element analysis. In this paper we explain our new approach
and present first numerical results for a simple laser cavity. The results are compared with those of a dynamic
multimode analysis using Gaussian eigenmodes.
We report on direct, absolute and spatially resolved temperature measurements in various diode-end-pumped laser crystals, using an infrared camera. Our measurement method requires careful calibrations of the camera, to take into account the emissivity of the crystals. We tested the repeatability of the calibration process, and the linearity of calibrations curves was verified to up to 100°C. We obtained good agreement between experimental results and finite elements analysis simulations done with LASCAD. We also studied and compared different types of thermal contacts and to measure the corresponding heat transfer coefficients using an Yb:YAG crystal. Finally we tried to highlight one of the major controversy concerning the comparison of the thermal behaviours of Nd:YVO4 and Nd:GdVO4 crystals.
For analyzing the properties of a laser, it is helpful to calculate the eigenmodes of the laser cavity. A new approach for modeling these eigenmodes is to approximate them by a finite element discretization of a 3D two-wave eigenvalue problem. In this paper, we analyze the properties of this model. First, we show that the two-wave eigenvalue problem is equivalent to an Helmholtz eigenvalue problem. Second, we analyze the stability of the finite element discretization and explain how to construct a suitable iterative solver. Numerical results are presented.
A new method for computing eigenmodes of a laser resonator by the use of finite element analysis (FEA) is presented. For this purpose, the scalar wave equation [Δ + k2]E(x,y,z) = 0 is transformed into a solvable 3D eigenvalue problem by separating out the propagation factor exp(-ikz) from the phasor amplitude E(x,y,z) of the time-harmonic electrical field. For standing wave resonators, the beam inside the cavity is represented by a two-wave ansatz. For cavities with parabolic optical elements the new approach has successfully been verified by the use of the Gaussian mode algorithm. For a DPSSL with a thermally lensing crystal inside the cavity the expected deviation between Gaussian approximation and numerical solution could be demonstrated clearly.
A theoretical model proposed for calculating the space-time deformation of laser pulses due to multiple scattering in particulate media is improved by dropping the small-angle approximation and extending the validity of the model to the description of multiple scattering into a full solid angle. The problem is reduced to the computation of the generalized functions used in the model, carried out through the use of the recursive relations employed in the original model. For the dominant forward scattering, the deviation between the two models is found to be small. The strong dependence of pulse broadening on the angle of observation is emphasized. The results received are confirmed by applying the generalized functions to typical cases of forward scattering.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.