Mirrors exhibit a finite propagation delay for reflected light

Group–delay dispersion measurement of laser mirrors by spectrally resolved white light interferometry. 1994. https://doi.org/10.1364/up.1994.md.23

It is known, that the temporal shape of a femtosecond pulse is altered while propagating through dispersive optical components and mirrors. Specially designed chirped dielectric high reflectors [1–3] have been proven to be efficient tools for controlling the intracavity group velocity dispersion in femtosecond lasers. In designing high performance femtosecond laser systems, the direct measurement of the frequency dependent group delay of mirrors is essential. Recently, a number of works have been devoted to the problem of measurement of the group–delay dispersion [4–9]. In [4,5] white light time–of–flight interferometer has been used. In [6,7] a phase locked Michelson interferometer was used to measure the phase response. Knox [8] measured the total group delay in an operating Ti: sapphire femtosecond laser by analyzing the pulse train with a digital frequency counter. Schwider [9] used superposition–fringes interferometry to determine the phase changes upon reflection from a dielectric multilayer. Spectrally resolved white light interferometry has been used for refractive index measurements of dye solutions [10]. In this paper a spectrally resolved white light Michelson interferometer is used to measure the group delay of mirrors.