Chirped Mirrors

When an ultrashort laser pulse passes through an optical system, its shape changes. Due to the wavelength-dependent dispersion, each individual wave is delayed to a different extent and differences in propagation time occur. As a result, the laser pulse broadens and the pulse energy decreases. To neutralize this effect, chirped mirrors are used.

LAYERTEC produces special dielectric systems (mirrors, pump mirrors, short-pass or long-pass filters, decouplers, etc.) with an adapted influence on the phase response (i. e. negative or positive GDD) in the wavelength range 200 – 5000 nm on customer request.

Phase correcting reflective systems with bandwidths, of a simple Bragg mirror (classical Lambda/4 mirror) or larger are called chirped mirrors. Phase-correcting mirrors for ps lasers with a (high) negative GDD over only a few nm bandwidth, on the other hand, are called GTI mirrors.

Chirped mirrors
  Schematic setup of a cavity-dumped picosecond laser with a Pockels cell

Chirped mirrors with a bandwidth on the size of a Bragg mirror can usually be calculated and fabricated without more oscillation of the GDD.

The larger the required bandwidth, the stronger the oscillation of the GDD. In these cases we recommend in principle the mutual compensation of this GDD oscillation with other optical components e.g. by a chirped mirror pair.