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Modeling of Pulse Amplification

Author: Dr. Paschotta

This tutorial treats in some detail various aspects of the amplification of light pulses – with particular focus on fiber amplifiers, but many details would be very similar for solid-state bulk amplifiers, as long as doped insulator laser gain media are used.

We carefully look at the underlying physics and also discuss various important practical aspects of numerical modeling for such devices. This could be very useful for those considering to construct such amplifier models themselves as well as for those using models made by others – for example, our product RP Fiber Power.

Click on the headings to get to the following parts of the tutorial:

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Part 1: Models for Different Pulse Duration Regimes

It depends largely on the pulse duration regime which effects need to be taken into account in the modeling of pulse amplification. We need to consider aspects like chromatic dispersion, optical nonlinearities and propagation times.

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Part 2: Gain Saturation

Depending on the operation regime of the amplifier, gain saturation by a single pulse may be strong or very weak, even completely negligible. If it is weak, we may still have substantial saturation by a fast pulse train. Different types of models are suitable for different situations.

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Part 3: Simulating Pumping and Pulse Amplification

One usually first needs to simulate the pumping process – supplying the amplifier with energy – before separately simulating the pulse amplification. We also consider some aspects of repetitive amplification, i.e., the amplification of pulse trains.

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Part 4: Multimode Amplifiers

Some additional aspects come into play when realizing amplifiers with multimode fibers: mode-dependent gain and for ultrashort pulses also intermodal dispersion.

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Part 5: Amplified Spontaneous Emission

ASE powers become substantially time-dependent in cases with strong gain saturation by single pulses. For this and other reasons, some surprising findings may be made.

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Part 6: Bulk Amplifiers

Compared with fiber amplifiers, bulk amplifiers can be used to obtain far higher output pulse energies and peak powers. They can be simulated with similar techniques.

By the way, on this website we have a lot of other materials on fiber optics – not only the other tutorials, but also a lot of encyclopedia articles on light pulses and various articles of the Photonics Spotlight.

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