Tapered diode laser and amplifier structures feature an intrinsic occurrence of different beam waist positions in lateral and vertical direction. The effect, described as astigmatism, shows a changing magnitude in dependence of the device working point. Different working points may therefore require different optical setups to achieve the desired beam shaping and will also affect the overall amplifier setup performance. This work investigates the influences of thermal and charge carrier induced changes to the optical device properties for tapered diode amplifier structures, based on gallium arsenide, at an emission wavelength of λ = 980 nm and a tapered section length of lT P = 4 mm. An advanced beam propagation algorithm was utilized to simulate the optical behavior of the device. To address the dominant influences of localized temperature change and charge carrier distribution the optical model is coupled to a thermal and electrical solver algorithm. General applicable astigmatism mechanisms are described which are based on the insights to the microscopic device functionalities. This includes the influence of different injection current densities, different thermal heat sink conductivities as well as heat spreading on top of the device. The theoretically established outcomes give insight to fundamental tapered amplifier mechanisms, necessary for better understanding of experimental results. Furthermore, the approach opens up the ability to optimize the optical setup which is used to shape the emitted radiation. At the same time limits of the tapered device design will be discussed.
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