| 摘要 |
A Laser system is disclosed which comprises a pump, wherein the laser system is adapted to be operated in pulsed operation so that at least one individual pulse of a temporally limited pulse duration (T o ) is generated, wherein the pulse ablates a material such that a debris cloud forms above the ablated material. Further, the pump power of the pump is modulated in such a way that the following three conditions are fulfilled:
(1) the intensity of the pulse oscillates between maximum values and minimum values during the pulse duration, wherein the laser pulse comprises a plurality of intensity maxima I max which occur at times {T i , i=1, ... N}; and a plurality of intensity minima I min which occur at times {t k , k=1, ... (N-1)}, wherein the intensity does not vanish at the intensity minima;
(2) the intensity oscillations of the laser pulse induce oscillations of the size of the debris cloud so that, during the pulse duration (T o ), there are at least two maxima of the size of the debris cloud which occur at times {Ä j , j=1, ... M} and which are located in between two intensity maxima of the laser pulse; and
(3) at least 70 percent of the maxima of the size of the debris cloud occur near an intensity minimum of the pulse such that, for at least 70 percent of the maxima of the size of the debris cloud, the intensity of the pulse I(Ä j ) at the time of the maximum of the size of the debris cloud is smaller than I min (t k ) + 0.5 x [I max (T i ) - I min (t k ) ], wherein I min (t k ) is the intensity minimum of the pulse which is closest to the maximum of the size of the debris cloud at time Ä j and I max (T i ) is the intensity maximum of the pulse which is closest to the maximum of the size of the debris cloud at time Ä j . |
