The invention relates to a device and a method for
mode selection and power amplification of a
broadband femtosecond laser. The device comprises a first
laser isolator sequentially located on an incident light path of the
broadband femtosecond laser, and is characterized in that a first total reflection mirror is sequentially arranged after the first laser
isolator, and a second total reflection mirror and an F-P cavity are sequentially arranged along an emergent direction of the first total reflection mirror; an emergent light path of the F-P cavity is sequentially provided with a third total reflection mirror, a fourth total reflection mirror, a half-wave plate and a
polarization beam splitter, and a reflection light path of the
polarization beam splitter is provided with a photoelectric
detector; a transmission light path of the
polarization beam splitter is sequentially provided with a first optical
grating, a diaphragm, a fifth total reflection mirror, a sixth total reflection mirror, a
laser diode and a second optical
grating; and a reflection light path of the second optical
grating is sequentially provided with a seventh total reflection mirror, a second
isolator, a first laser shaping
prism and a second shaping
prism. According to the whole device and the method provided by the invention, excellent
Gaussian type small-amount or single-mode high-power pulse laser with very small spot size can be outputted.