In this paper, the concept of a mesoscopic method with high-speed and high-sensitivity is proposed for characterization of surface defects for large optics. The technology is a comprehensive integration of laser scattering method and highly sensitive photothermal method. The principle, experimental setup and preliminary measurement results are presented in detail in the paper. A statistical model for evaluation of mapping results of defects is also proposed to show the effectiveness of the comprehensive metrology method. The proposed method can detect non-destructively surface defects with high-speed and high-sensitivity at the mesoscopical level. It is a promising novel tool for mapping defects in meter size optics and hence it can provide clues to eliminate defects during the manufacturing processes and march toward “defect-free” optics.
A new method is proposed to inspect the subsurface damage (SSD) that plays a key role on improving the laser induced
damage threshold (LIDT) of optics applied in high power laser system. This method is based on total internal reflection
microscopy (TIRM) and digital image processing technique. Because of relatively small depth of focus of a microscope
at large magnification, a series of TIRM images can be obtained while the microscope focuses into different depths of
sample by micro-focusing control. Definition of each image is calculated through wavelet transform. The relation
between definition of TIRM images and the depth of SSD is established. According to the definition curve, the position
and size along the depth direction can be acquired simultaneously. The measurement accuracy is dependent on the depth
of field of microscope. This proposed method has been applied to measure the SSD information of finished K9 glass,
fused silica glass and Nd-doped glass.
We use the time-resolved degenerated PO pump-probe technique to investigate the nonlinear absorption and nonlinear refraction dynamics of a novel porphyrin derivate, Indium-Porphyrin functionalized with polymethylmethacrylate (InPor-MMA26), dissolved in DMF at 532 nm in picosecond domain simultaneously. The results indicate that the nonlinear optical responses are induced by solution molecular excited state nonlinearity only, without the existence of two-photon absorption or Kerr refraction. Combined with five-energy-level model, all nonlinear optical parameters are determined by analyzing the experimental curves and confirmed by 4 ns Z-scan at 532 nm. The sample has a good reverse saturable absorption and reasonable positive refraction. With the proper lifetime and intersystem crossing time, this sample can be a candidate for optical limiting. The polymer attached to porphyrin directly by chemical bonds. This makes it have better homogeneity compared to physical mixing in the form of film.