[19p-PA2-1~9] 3.7 Laser processing

[19p-PA2-4] Characteristic property of annular beam from mode converter for ultrashort pulse laser

〇(M2)Ryo Saito¹, Godai Miyaji¹ (1.Tokyo Univ. of A & T)

Keywords:annular beam, few-cycle pulse laser, laser nanoprocessing

For laser material processing with few-cycle laser pulses, a reflective objective should be used to avoid decrease in the peak intensity of the pulse induced by the pulse extension. In this work, we developed the annular beam converter consisting of chirp mirrors, concave axicon mirrors, quarter waveplates, and a thin film polarizer. The pulse duration and beam intensity profile were measured. With the converter, the output was the 15.1-fs pulses with an annular beam pattern. The results obtained indicate that the annular beam avoids the insertion loss of the reflective objective, leading to the laser material nanoprocessing with a high peak intensity.