Thermal process of 1064 nm millisecond pulsed Nd:YAG laser irradiated silicon was time-resolved temperature measured by an infrared radiation pyrometer, temperature evolutions of the spot center for wide range of laser energy densities were presented. The waveforms of temperature evolution curves contained much information about phase change, melting, solidification and vaporization. An axisymmetric numerical model was established for millisecond laser heating silicon. The transient temperature fields were obtained by using the finite element method. The numerical results of temperature evolutions of the spot center are in good agreement with the experimental results. Furthermore, the axial temperature distributions of the numerical results give a better understanding of the waveforms in the experimental results. The melting threshold, vaporizing threshold, melting duration, and melting depth were better identified by analyzing two kinds of results.

An axisymmetric mathematical model was established for millisecond-pulsed Nd:YAG laser heating of silicon-based positive-intrinsic-negative photodiode. The transient temperature fields were obtained by using the finite element method. The temperature dependences of the material parameters and the absorption coefficient were taken into account in the calculation. The results indicate that the optical absorption coefficient and the thermal conductivity are the two key factors for the temperature evolution. The diffusion of boron in the liquid phase and the introduction of deep-level defects in the depletion region of the photodiode were the two reasons for the millisecond laser-induced electrical degradation of the photodiode. The morphological damage threshold and electrical degradation threshold of the photodiode were obtained numerically. Meanwhile, the influence of the antireflection coating, the doping concentration, and the junction depth were also considered. The results show that the morphological damage threshold decreases with adding an antireflection coating, the increase of the doping concentration, and junction depth. The electrical degradation threshold increases only with the junction depth.

The laser–silicon interaction process was investigated with the superposed radiation of two pulsed Nd:YAG lasers. A pulse duration of 1 millisecond (ms) was superposed by 7 nanosecond (ns) pulses, creating a combined pulse laser (CPL). The time-resolved surface temperature of silicon was measured by an infrared radiation pyrometer. The melting thresholds of silicon were attained for a single ms laser and a CPL by infrared radiometry and time-resolved reflectance. The concept of threshold boundary was proposed, and a fitted curve of threshold boundary was obtained. An axisymmetric model was established for laser heating of silicon. The transient temperature fields were obtained for single ms laser and CPL irradiation using finite element analysis. The numerical results were validated experimentally, and an obvious decrease in melting threshold was found under CPL irradiation. That is attributed to pre-heating by the ms laser and the surface damage caused by the ns laser.

The surface damage morphologies of single-crystal silicon induced by a combined pulse laser (CPL) and a single millisecond laser are investigated, respectively. The CPL includes a millisecond (ms) laser superposed by a nanosecond (ns) laser. Inspected by an optical microscope, it was found that the surface damage was more serious when the sample was irradiated by the CPL than by a single ms laser with the same incident laser energy. Besides surface cleavage, obvious ablation and fold areas were discovered by CPL irradiation. A two-dimensional spatial axisymmetric model was established to assess the difference between single ms laser and CPL irradiation and explain the generation mechanism of the different surface damage. This was attributed to the preheating effect by the ms laser and the surface damage caused by the ns laser.

A three-dimensional model was established to simulate the process of a millisecond Nd:YAG laser irradiating the CCD, based on its array and multilayer structure. The transient temperature and thermal stress field of the CCD were calculated by using the finite element method. The temperature dependence of material parameters was taken into consideration in the calculation. The results indicated that coupling of the heat damage and thermal stress damage was the main reason for the millisecond laser damage CCD. Softening of the PMMA microlens or rupture of the silica microlens reduced the fill factor of the CCD. Plastic deformation of the silicon substrate increased a great deal of dark current. The leakage current was introduced due to the peeled Al shield. Most importantly, the melting through of the Al-shield layer and the fracture of the silica insulating layer are the two critical factors for functional damage to the CCD. Meanwhile, the influence of the material and fill factor of the microlens was also considered. The results showed that plastic damage of the silicon substrate was more dramatic than the PMMA microlens CCD. And the damage threshold decreased along with the increasing fill factor.

The near infrared (NIR) laser drilling of a carbon fiber reinforced polymer (CFRP) composite in the continuous wave (CW) mode and the ms pulse mode was investigated by an experiment and a numerical simulation. The relationships between the laser penetrating time, entrance hole diameter, surface heat affected zone (HAZ) width, and material ablation rate and the laser irradiation time and laser peak power densities were obtained from the experiment. For the same average power density of the laser output, 3.5 kW/cm², it was found that the ms pulse laser mode, which had a higher peak power density, had a higher drilling efficiency. When drilling the same holes, the pulse laser mode, which had the highest peak power density of 49.8 kW/cm², had the lowest drilling time of 0.23 s and had the smallest surface HAZ width of 0.54 mm. In addition, it was found that the laser penetrating time decreased sharply when the peak power density was higher than 23.4 kW/cm². After analyzing the internal gas pressure by the numerical simulation, it was considered that a large internal gas pressure appeared, which resulted from polymer pyrolysis, causing a large amount of the mechanical erosion of the composite material to improve the drilling efficiency. Therefore, the ms pulse laser showed its potential and advantage in laser drilling the CFRP composite.