Apparatus and method of high power nanosecond mode-locked solid state laser

A mode-locked solid state laser apparatus, comprising:

• an optical film receiving a pumping light having a first wavelength incident in a first direction;
• a gain medium crystal receiving the pumping light passing the optical film, and generating an initial laser beam having a second wavelength, wherein the initial laser beam forms a first optical path starting at one end thereof from the gain medium crystal;
• a concave mirror, disposed on the other end of the first optical path opposite to the one end of the first optical path, and reflecting the initial laser beam along a second optical path starting at one end thereof from the concave mirror,
• a Fabry-Perot element, disposed on the other end of the second optical path opposite to the one end thereof, and reflecting the initial laser beam back to the concave mirror so as to reflect the initial laser beam by the concave mirror along a third optical path starting at one end thereof from the concave mirror, wherein the Fabry-Perot element includes a first surface and a second surface parallel to the first surface, and the first surface is closer to the concave mirror when compared to the second surface;
• and
• an output coupler disposed on the other end of the third optical path opposite to the one end thereof, and reflecting the initial laser beam back to the concave mirror along the third optical path.

A method for adjusting a pulse width of a solid-state laser pulse, comprising steps of:

• providing a solid state laser device, including:
• an optical film receiving a pumping light having a first wavelength incident in a first direction;
• a gain medium crystal receiving the pumping light passing the optical film, and generating an initial laser beam having a second wavelength, wherein the initial laser beam forms a first optical path starting at one end thereof from the gain medium crystal;
• a concave mirror, disposed on the other end of the first optical path opposite to the one end thereof, and reflecting the initial laser beam along a second optical path starting at one end thereof from the concave mirror,
• a Fabry-Perot element, disposed on the other end of the second optical path opposite to the one end thereof, and reflecting the initial laser beam back to the concave mirror so as to reflect the initial laser beam by the concave mirror along a third optical path starting at one end thereof from the concave mirror, wherein the Fabry-Perot element including a first surface and a second surface parallel to the first surface, wherein the first surface is closer to the concave mirror when compared to the second surface and has a first relatively high transmittance, and the second surface has a first relatively high reflectivity;
• and
• an output coupler disposed on the other end of the third optical path opposite to the one end thereof, and releasing the solid-state laser pulse having the pulse width;
• and
• controlling the thickness to adjust the pulse width.