Patent ID: 8761214

Claim:
An apparatus for stabilizing second harmonic wave pulse output in a laser system operating by pulses, the apparatus comprising: a pulse laser oscillator for outputting a first laser pulse; non-linear crystals for converting the first laser pulse having a first wavelength into a second laser pulse having a second wavelength being half the first wavelength and outputting the second laser pulse; a light absorption filter for absorbing energy of the second laser pulse and outputting a third laser pulse having an energy lower than the second laser pulse; moving means for moving the light absorption filter away from a laser path and selectively placing the light absorption filter on the laser path; and a control unit for controlling the moving means to adjust the energy of the second laser pulse according to a selected energy mode, wherein the control unit comprises: an energy mode selection unit for receiving the energy of the second laser pulse; at least one position sensor for outputting position signals of the light absorption filter; a controller for generating control signals to control the moving means based on the position signals and the energy of the second laser pulse wave received from the energy mode selection unit.