Design of dielectric high-reflectors for dispersion control in femtosecond lasers

Chirped dielectric rugate mirrors have been constructed for broadband dispersion control in femtosecond laser oscillators by the use of Fourier transform. Dispersive properties of the mirrors are tailored and explained on the basis of the time shifting theorem of Fourier analysis. Depending on their construction parameters, these chirped gradient-index structures may exhibit high reflectivity and nearly constant negative, i.e. anomalous group delay dispersion over frequency ranges well beyond the fluorescence bandwidths of broadband laser- active materials available to date. As a consequence, practical implementation of these novel dispersive devices would permit the full utilization of the bandwidth offered by these broadband gain media, and allow the construction of small size, compact femtosecond solid state laser oscillators generating optical pulses shorter than could have been achieved so far, directly from the laser oscillator.