[The influence of laser induced damage points on characters of the laser transmission]

The production and increase of damage points in optical components under high energy repetitive pulsed lasers is closely dependent on the effects of light beam intensity modulation. In the present paper, the appearance of laser-induced damage points on surface of K9 glass was observed. The damage is increased toward center. In this way, the center of the focus of laser beam is fully cracked, and the shell-like factures and the refractive-index changing region, which is caused by phase transition, are arranged outward orderly. The transmittance spectrum through the K9 glass and damage point were measured, indicating that the optical transmittances can reduce by over 20% and the declining rate is related to the area of damage points instead of the wavelength, which means that the full fracture of the material will absorb laser energy completely and is similar to the black body. The laser density detection with CCD shows that the damage points can cause the distortion of laser transmission and the scattering effect plays a major role. This kind of modulation effects by damage points can cause inhomogeneity of the laser light intensity distribution, which can induce diffusion of damage in optical components.