4. Conclusion

In this article, we have reviewed a number of methods for characterizing an ultrashort pulse, assuming from the outset that the pulse is much shorter than the response time of the photodetection system. By limiting ourselves to the case of integrating detectors, we were able to establish that the characterization device had to include either a non-stationary or a non-linear element. This result enabled us to classify measurement methods into two categories, depending on whether or not a suitable reference pulse is available. In the first case, the reference pulse provides the required non-stationary phenomenon, and it is possible to obtain a signal that is a linear function of the electric field, whose reconstruction is then immediate. In the second case, a second- or third-order nonlinear optical process is used to perform a self-referential characterization of the pulse, in some cases...