Multilayer Thin Films Dielectric Double Chirped Mirrors Design

The double chirped mirror DCM appeared to meet the need to compensate for the gain crystal dispersion of solid state lasers in a broad wavelength range. Compared to earlier dispersion compensation techniques, they enabled remarkable improvements in the field of generating ultra short pulses. When ultra broad band gain media are used inside laser cavities, cavity dispersion plays an important role in determining the duration of the pulses when the laser is operating in mode locking regime. The aim of these notes is then to investigate which the act of cavity dispersion is on the shape and duration of a laser pulse that is propagating inside a femtosecond laser cavity, and how this dispersion can be compensated with the aid of suitable optical systems. In this paper a simple analytical equation takes an arbitrarily group delay dispersion GDD as an input function and gives the chirp law as an output. The chirp law determines the local Bragg wavelengths in the mirror. It allows the calculation of the thicknesses of the high and low index layers if the double chirp of the layers in the front part of the mirror is taken into account. A simple chirped mirror (CM) can be achieved through dielectric coating with alternate layers of high and low index materials such as TiO2/SiO2 or TiO2LZH/SiO2LZH with varying thicknesses.