503 Angular dependence of coupling between focused laser pulses and a transparent material studied by time-resolved imaging technique

Abstract

Short and intense Iaser pulse can process the surface and the inside oftransparent materials by focusing the pulse at desired position. Processing ofsuch a transparent material is considered to be app]icable to a lot of practica] applications.Details of such process are, however, still unclear and are subjects of fhrther investigations. Here we report on dynamical observation about interaction of fundarnental radiation (1064nm) of the Q-switched Nd:YAG laser to the surface of PMMA obseryed by an imaging system with nanosecond time resolution, The system uses fundamental radiation ofa Q-switched Nd:YAG laser as a processing laser and second harrnonic radiation (532nm) of another Nd:YAG laser as illuminating light.We observed stress wayes which propagate into the material and into the atmosphere by shadowgraph, schlieren and photoelastic method.We distinguished three different types of waves propagating into the bulk samples.The contrast of photoelastic images depends on raser pulse energy, Based on this result, we try to examine the effects of incidence angle of the laser to coupling between ]aser radiations and the material and found that magnitude ofstress wave correlates with laser fluence.

Energy Model in Laser Processing of a Cylindrical Grinding Wheel

“…The wheel tested in the research was cylindrical, and the position of laser irradiation greatly influenced the amount of energy absorbed/scattered and was thus an important processing parameter. In a number of studies [3,4], the laser beam was applied vertically with respect to the surface of the wheel, i.e., at an incident angle of zero. However, different incident angles applied to the area of the wheel impart different levels of energy to the wheel [5,6].…”

Absorbed energy in laser truing of a small vitrified CBN grinding wheel

“…In a number of studies [9][10][11], the laser beam was applied vertically with respect to the surface of the workpiece (referred to as "vertical irradiation"), i.e. at an incident angle of zero.…”

“…However, laser processing has been used in various applications and the incident angle is not always vertical. Different incident angles applied to the same area of the workpiece impart different levels of energy to the workpiece [9][10][11]. In the present study, energy absorption models were developed that take into account the space distribution of laser energy absorbed/scattered by the cylindrical surface of the workpiece.…”

Energy-Mode Adjustment in Laser Processing a Small Vitrified CBN Grinding Wheel

“…However, laser processing has been used in various applications, and the incident angle is not always vertical. Different incident positions applied to the focal area of the wheel impart different levels of energy to the wheel [4][5][6]. In the present study, energy models were developed that take into account the energy mode of laser energy absorbed by the circular profile of the wheel.…”