Frequency-doubled laser and method of generating harmonic laser

A method of generating harmonic laser using a frequency-doubled laser comprising a first reflecting mirror, a second reflecting mirror, a gain medium, a telescope module, a polarizing element, and a nonlinear crystal;

• wherein the first reflecting mirror and the second reflecting mirror are spaced apart to form a resonator of the frequency-doubled laser;
• the polarizing element, the gain medium, the telescope module, and the nonlinear crystal are located in the resonator, and the telescope module is located between the gain medium and the nonlinear crystal, the method comprising:
• setting a focusing quantity Δ of the frequency-doubled laser to be 0, wherein the focusing quantity Δ is L−(f1+f2), L is a distance between a first cavity lens and a second cavity lens, f1 is a focal length of the first cavity lens, and f2 is a focal length of the second cavity lens;
• exciting the gain medium to output a fundamental frequency laser, and detecting a luminous energy of outputted harmonic laser;
• adjusting the focusing quantity Δ in a forward or a reversed direction, and adjusting the focusing quantity until the harmonic laser output is stopped;
• and
• selecting a position with a maximum harmonic outputting energy, acquiring a position of an optimal focusing quantity, and outputting the harmonic laser.