Many significant breakthroughs in ultrafast-laser technology have been made possible by improvements in ultrafast laser optics, specifically in the development of thin-film dielectric coatings and processes. Despite these improvements, electron-beam evaporation, magnetron sputtering, and other fabrication techniques are still prone to deposition errors. In an effort to minimize those errors and improve dielectric-mirror design, researchers from Ludwig-Maximilians-Universität München (Munich, Germany), Ultrafast Innovations (Garching, Germany), and Moscow State University (Moscow, Russia) have developed a new robust synthesis method that can be used to design dispersive mirrors that are impossible to produce using conventional needle optimization techniques.
The robust synthesis method is essentially a generalization of very efficient needle optimization and gradual evolution techniques, and is based on a simultaneous optimization of spectral characteristics of multiple designs located in a small neighborhood of the main or pivotal design. Using the method and a conventional needle optimization technique, the research team fabricated dispersive mirrors operating from 690–890 nm with a dispersion of -300 fs2 at 800 nm. The mirror fabricated using the robust synthesis method had much lower sensitivity to deposition-layer thickness errors and exhibited much-less-pronounced resonance errors. Contact Vladimir Pervak at [email protected].