Short-pulse lasers are often used in time-resolved measurements with pulse lengths in the fs range. They are also commonly used in material processing. The special properties of interaction between short pulses and matter are utilised for this purpose.
Mirrors with coatings that have a large bandwidth and low dispersion are required for these fs lasers. The shorter the pulse length, the more the bandwidth of a pulse increases. The bandwidth is, therefore, significantly larger in the fs range than in the ns range. In mirrors this is achieved through material selection - the larger the difference in refractive index between material and coating, the larger the bandwidth.
In order not to expand the pulse more than necessary in a reflection, low dispersion properties of the coating are of the utmost importance. This requirement is achieved by the use of an inexpensive single stack coating. Substrates are coated with uniform ¼ layers, resulting in a small so-called GVD value. The group velocity dispersion is low because the incident laser beams are reflected with practically the same phase.
In partially reflecting mirrors the dispersion properties of the substrate into which the laser beam enters should also be kept in mind. Thin quartz glasses are almost exclusively used for these mirrors.
LASER COMPONENTS’ in-house production offer mirrors ranging from end mirrors, output couplers, and beam splitters to pump mirrors that also have high transmission values at popular pump wavelengths (488 nm - 532 nm). Furthermore, wedge substrates are available designed to help avoid back reflections entering the cavity.
This comprehensive program of fs laser optics is supplemented by beam splitters for auto correlators, broadband polarisers with the lowest dispersion possible, quartz glass lenses, Brewster prisms for beam compression, and metal mirrors for very wide reflection ranges. Detailed information can be provided by our sales engineers, but have a look first at our new Optics catalogue.
