Silver Mirrors for fs Laser Optics

Silver Mirrors optimized for Femtosecond Applications

silver mirror for fs-lasersFigure 1: Reflectance (a) and GDD-spectrum (b) of a silver mirror optimized for use with fs-lasers in the wavelength range 600 – 1000 nm (AOI = 0°)
silver mirror for fs-lasersFigure 2: Reflectance (a) and GDD-spectra (b) of a silver mirror optimized for use with fs-lasers in the wavelength range 600–1000nm (AOI=45°)

Special Features:

  • High reflectance in the VIS and NIR
  • Very broad reflectance band with GDD ∼ 0fs2
  • Silver mirrors with defined transmission (e.g. 0.01%) show high LIDT-values (see table 1) and the same R and GDD values as shown in figures 1 and 2
  • Extremely low straylight losses (TS ∼ 3x10-5 in the VIS and NIR)
  • Lifetimes of more than 10 years in normal atmosphere were demonstrated
  • Highly stable optical parameters because of sputtered protective layers
  • Good cleanability (tested according to MIL-M-13508C § 4.4.5)
  • Laser induced damage threshold for fs-pulses:
CoatingReflectance*Wavelength rangeLIDT [J / cm2]**
fs- optimized protected silverR = 96.5 ... 98.5 %600 - 1000 nm0.38
Enhanced silver 800 nmR > 99 %700 - 900 nm0.37
Broadband enhanced silver2R = 98 … 98. 5 %600 - 1200 nm0.24
Partially transparent silverR = 96.5 % - 98.5 %600 - 1000 nm0.22
*For unpolarized light at AOI = 45°
** Measurements were performed at Laser Zentrum Hannover according to ISO 11254 measurement
conditions: pulse duration: 150 fs, 30 000 pulses, repetition rate 1kHz, λ = 800 nm
Stock of Standard Components:
  • Standard and fs - optimized protected silver on substrates with ∅ =12.7mm, ∅ = 25mm and ∅ = 50mm:
    • Plano,
    • Plano /concave and plano / convex with a variety of radii between 10mm and 10000 mm
  • Other sizes, shapes, radii and coatings for other wavelengths ranges on request

Silver Mirrors with Enhanced Reflectivity

The reflectance of silver mirrors can be enhanced by a dielectric overcoat. The bandwidth of the enhanced reflectivity must be exactly specified. Outside this band the reflectivity of the mirror may be lower than that of a standard silver mirror. For use with fs-lasers, the dielectric overcoat must be optimized for high reflectivity and low GDD. The following figures show examples for silver mirrors with enhanced reflectivity at a specified wavelength (figures 3 and 4) and over the wavelength range of the Ti:Sapphire laser (figure 5).

Also enhanced silver mirrors can be designed for a defined transmission (e.g. T = 0.01 %).

silver mirror for fs-lasersFigure 4: Reflectance (a) and GDD-spectra (b) of silver mirrors with enhanced reflectivity around 800 nm (AOI = 45°)
silver mirror for fs-lasersFigure 3: Reflectance (a) and GDD-spectra (b) of silver mirrors with different designs for enhanced reflectivity around 850 nm (AOI = 0°)
silver mirror for fs-lasersFigure 5: Reflectance (a) and GDD-spectra (b) of silver mirrors with enhanced reflectivity in the wavelength range 600 – 1200 nm (AOI = 45°)