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Dispersion Measurements on Dielectric MirrorsBroadband mirrors are widely used in ultrafast laser setups because of their high reflectivity over a broad range of wavelength. However, most of such broadband mirrors, especially those with dielectric coatings, are not dispersion-free within the range of high reflectivity. What makes it even worse is that their dispersion depends on the laser beam incidence angle! The figure shows an example of group delay measurements on a broadband dielectric mirror, done within the range of a typical Ti:Sapphire oscillator. The relative group delay spectrum for a single bounce off the mirror surface features three distinct resonances, which are known to be the result of Gires–Tournois interference between reflections coming from different layers of the dielectric coating. It is needless to say that such phase distortions have a dramatic effect on the laser pulse properties. [Read more]Links to references: [1] D. Pestov et al., "Single-beam shaper based pulse characterization and compression using MIIPS sonogram," Opt. Lett. 35, 1422 (2010). [2] N. Matuschek et al., "Theory of double-chirped mirrors," IEEE J. Sel. Top. Quantum Electron. 4, 197 (1998). |
