Method and device for excavating submerged stratum

A device for excavating a submerged stratum including:

• first laser oscillation means;
• second laser oscillation means;
• laser transmission means;
• and
• laser irradiation means,
• wherein the first laser oscillation means outputs at least one of a pulsed laser beam and a continuous-wave laser beam and adjusts at least one parameter selected from a group consisting of a laser pulse energy, a laser beam quality, a laser pulse width, a laser frequency and a laser wavelength, the second laser oscillation means outputs at least one of the pulsed laser beam and the continuous-wave laser beam and adjusts a laser frequency and a laser wavelength, and
• the first laser oscillation means induces laser-induced force and laser irradiation in liquid that generates a bubble near an end of an output section of the laser irradiation means, and the second laser oscillation means generates thermal effect on the submerged stratum by a beam passing through the bubble.