Components for higher harmonic of Ti:Sapphire laser

Components for the Higher Harmonic of Ti:Sapphire Laser

The fourth and fifth harmonics of the Ti:Sapphire laser provide fs-pulses in the DUV / VUV range. These offer a variety of applications in spectroscopy as well as in materials science. Optics for these very special applications must be optimized for high reflectivity and low dispersion.

Turning Mirrors and Separators for the Fourth Harmonic

turning mirror for 200nmFigure 1: Reflectance (measured, a) and GDD - spectra (calculated, b) of a turning mirror for 200nm (AOI = 45°)
separator for the fourth harmonicFigure 2: Reflectance (a) and GDD - spectra (b) of a separator for the fourth harmonic from the longer wavelength harmonics and the ground wavelength (AOI = 45°)

Components for the Fifth Harmonic

turning mirror for 160nmFigure 3: Reflectance (measured, a) and GDD - spectra (calculated, b) of a turning mirror for 160nm (AOI = 45°)

Special Components

separator with high reflectivity in a small wavelengthFigure 4: Reflectance (a) and GDD - spectra (b) of a separator with high reflectivity in a small wavelength range in the VIS and high transmission for the third and fourth harmonics of the Ti:Sapphire laser:
HRs(45°, 420nm) > 99% + Rp(45°, 200 + 270nm) < 3%

Properties of Femtosecond UV Coatings

  • Depending on the wavelength range of the ground wave the coatings described in the data sheets on the pages 68–71 can be used for the following centre wavelengths:
    • Third harmonic: 250 – 330 nm
    • Fourth harmonic: 180 – 250 nm
    • Fifth harmonic: 150 – 180 nm
  • Bandwidths of the coatings are given in the table below
  • Coatings are optimized for broad reflection bands, high reflectivity and low GDD
  • Different substrate and coating materials depending on the wavelength range; components for 220 nm and below consist of fluoridic layer systems on CaF2 - substrates
Bandwidth of the High Reflectance and Low GDD range
ComponentWavelength rangeP-polarizationS-polarization
R > 99 %, |GDD| < 20 fs2R > 99. 5%, |GDD| < 20 fs2
Turning mirror 3rd harmonicUV30 nm50 nm
Separator 3rd harmonicUV30 nm50 nm
Dual wavelength turning mirrorUV15 nm26 nm
UV / VIS34 nm72 nm
Turning mirror 4th harmonicUV5 nm (R > 93 %)15 nm (R > 97 %)
Turning mirror 5th harmonicUV4 nm (R > 90 %)12 nm (R > 97 %)