Abstract
We describe a method for retrieving spectral phase information from second harmonic interferometric autocorrelation measurements supplemented by the use of the observed spectral intensity. By applying a combination of graduated optimization and genetic algorithms, accurate phase retrieval of laser pulses as short as a few optical cycles was obtained from the measured autocorrelation and spectral intensity. The effectiveness of the combined algorithms is demonstrated on a set of significantly different femtosecond pulse shapes.
Highlights
Measurement of ultrashort laser pulse shapes is an important non-trivial task
There are several methods allowing for the full characterization of the electric field [1,2,3]; the most common of these measuring methods include second harmonic interferometric autocorrelation (SHIAC) [1], frequency resolved optical gating (FROG) [2] and spectral interferometry for direct electric-field reconstruction (SPIDER) [3]
Naganuma et al [5] have shown that the knowledge of both SHIAC trace and spectral intensity are sufficient for pulse reconstruction
Summary
Measurement of ultrashort laser pulse shapes is an important non-trivial task. There are several methods allowing for the full characterization of the electric field [1,2,3]; the most common of these measuring methods include second harmonic interferometric autocorrelation (SHIAC) [1], frequency resolved optical gating (FROG) [2] and spectral interferometry for direct electric-field reconstruction (SPIDER) [3]. GOA as a global searching algorithm, reduces a complex problem into a much simpler one It makes a more detailed optimization in the vicinity of the extrema of the previously simplified problem and repeats this process until the original problem is optimized to a specified precision. In this way, GOA can search a big parameter space and provide GA with a good starting point that is around the global optimum. A method is presented that combines GOA with GA so as to avoid local extrema and reach an accurate optimization solution efficiently We find this algorithm to be well-suited for retrieving phase information from SHIAC and spectral intensity measurements.
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