超短脉冲激光技术-1.docxVIP

Research – Ultrashort Pulse Laser Technology E. P. Ipren, J. G. Fujimoto and F. X. Current Ultrashort pulse lasers are an enabling technology for a whole range of fundamental and applied research areas as well as industrial applications. The pulse width typically ranges from picoseconds down to few femtoseconds in duration. To generate such short pulses typically multiple longitudinal modes in a laser resonator are excited, such that a pulse much shorter than the cavity roundtrip time is created inside the laser resonator. The shortest pulse that can build up is then limited by the gain bandwidth of the amplifying medium. Figure 1 shows the progress in generating short optical pulses from various laser materials. Over the last decades, our group has made major contributions to both the understanding of the pulse generation mechanisms involved in the various types of lasers and the emerging technologies leading to shorter and shorter pulse durations. Figure 1—Progress in short pulse generation since the invention of the laser. The progress of pulse shortening culminated in the generation of the shortest pulses directly from a laser oscillator approaching a single optical cycle at 800 nm from Kerr-lens mode-locked Ti:sapphire lasers, developed in our group. Figure 2—Setup of octave spanning Ti:sapphire laser using double-chirped mirror pairs for dispersion compensation. Intra cavity optical components and the air in the laser resonator. The broadband mirrors are designed in pairs (green and blue), called double-chirped mirror pairs. They have a custom designed group delay over one octave of bandwidth as well as a high reflectivity over the same bandwidth and one of them has a pump transmission window to transmit the pump light into the cavity (see Figure 3 Figure 3—High reflectivity and precise dispersion compensation with double-chirped mirror pairs. Figure 4(a) shows a up-converted spectral interferogram obtained using the two-dimensional spectral shearing (2DSI)