Microjoule pulse energy from a chirped-pulse Ti:sapphire oscillator with cavity-dumping

Abstract

A number of applications ranging from micro-machining to non-linear frequency conversion and high harmonic generation (HHO) would significantly benefit from femtosecond laser sources with pulse energies in the Ill-regime with MHz repetition rate at pulse durations below 100 fs. To this end in recent years several different concepts have been developed [1][2][3].Here we report for the first time to our knowledge on a chirped-pulse Ti:sapphire laser oscillator with acoustooptical cavity-dumping that reaches pulse energies in excess of IIII at a repetition rate of 1 MHz and with a spectral width supporting pulse durations below 80 fs. After the laser, a cw-pumped, cryogenically cooled amplifier is used to further increase the pulse energy up to 1.5 Ill. In this contribution we will discuss possible setups and designs for energy scaling up to several microjoules.A schematic layout of the laser is shown on the left hand side of Fig. 1. The laser oscillator is built in a standard z-configuration with a Herriott-cell to allow for compact design. It has an internal repetition rate of 25.6 MHz from which the pulses are picked with a 1 MHz repetition rate with the help of the AOM. SESAM CoIlerent Verdi 16W@532nm to experiments r ·20 I .JÕ Ĩ~I Lo t Ĩ~I '~I ""9;5 780 790 7'9S 8CX:l 805 810 815 wa\'elength 10m) Fig. 1. (left) Laser setup; (right) Optical spectrum of the laser pulses.The laser is operated with a pump power of 16 Wand a net positive intra-cavity dispersion of 650 fs 2 in order to ensure chirped pulse operation and to avoid detrimental nonlinearities . The right hand side of Fig. 1 shows the spectrum of the output laser pulse which supports a Fourier limit of74 fs. Because of the chirped pulse operation the actual pulse length behind the oscillator is about 5 ps. These out-coupled pulses are subsequently used in a single stage cw-amplifier currently pumped with 10.5 W which is sufficient to further amplify the pulse energy to 1.5 III without any change in the spectral shape or width. With more pump power available, we expect power scaling into the multi-Ill range.References: