| Zugriffsnummer | 33474 |
| Dokumenttyp | Zeitschriftenartikel |
| Sprache | Englisch |
| Titel | Induced transmittance of eye-protective laser filters |
| Autor(in); Institution |
Koschinski, Willi; 4.21, Bildoptik und Spektrometrie, PTB-Braunschweig
Schirmacher, Alfred; 4.21, Bildoptik und Spektrometrie, PTB-Braunschweig
Sutter, Ernst; 4.21, Bildoptik und Spektrometrie, PTB-Braunschweig
|
| Quelle/Jahr | Journal of Laser Applications: 10 (1998), 3, 126 - 130 |
| ISSN | 1042-346X (PRINT) ; 1938-1387 (ONLINE) |
| DOI | |
| Verlag | Woodbury, NY: AIP |
| Freie Schlagworte | lasers ; laser filters ; induced transmittance ; eye safety |
| Zusammenfassung | Different kinds of eye-protective laser filters were investigated with short laser pulses with respect to their transmittance and stabilityin dependence on the irradiance. The irradiance was varied between 3 × 106 and 3 × 1013 W/m². The investigations were performed at the wavelengths of 1064 and 532 nm using a Nd:YAG laser with a pulse duration of 15 ns and at a wavelength of 798 nm generated by a Ti:Sa laser with a pulse duration of about 250 fs. For filters based on semiconductor-doped glasses, an increase in the transmittance was observed with increasing irradiance at 532 nm. It extends over six orders of magnitude due to the saturation of the absorption. A similar dramatic effect was measured also on polycarbonate filters at 1064 nm. The dependence of the transmittance on the irradiance is discussed in a phenomenological model to show the importance of the relaxation time, the concentration of the absorption centers, and the absorption cross section forthe nonlinear behavior. Taking into account two absorption processes,a complete fit of the measured irradiance-dependent transmittance is achieved. Thermal effects due to the absorbed energy can be neglected compared with the nonlinear optical behavior: Either no damage to the sample surface is observed at all or it is observed only after many pulses hit the surface. In the case of a surface damage, the regular transmittance will first decrease due to increased scattering of light and then increase due to removal of material. In the experiments with the fs Ti:Sa laser system, the destruction of the filter surface starts with the very first pulses in many cases. This becomes important for eye-protection filters using reflecting dielectric coatings. |
