Laser ignition device

A laser ignition device comprising:

• a laser oscillation optical system configured to produce a pulsed laser light;
• a condensing optical element configured to condense the pulsed laser light into a combustion chamber;
• a housing internally containing the condensing optical element;
• and
• an optical window provided distally with respect to the condensing optical element in the housing and configured to transmit the pulsed laser light, wherein
• the pulsed laser light is shaped as a ring around an optical axis at least at a light passage position in the optical window,
• the laser oscillation optical system includes an axicon lens configured to transform incident light into outgoing light shaped as the ring around the optical axis,
• the laser oscillation optical system includes an excitation light source configured to generate excitation light, the axicon lens configured to receive and transform the excitation light into the ring-shaped outgoing light, a collimator lens configured to transform the ring-shaped outgoing light into collimated light parallel with the optical axis, and a laser resonator configured to be excited by the excitation light received as the collimated light to emit the pulsed laser light, and
• the laser resonator includes an inert medium formed in an area including the optical axis and a cylindrical medium formed around an outer periphery of the inert medium, and a refractive index of the cylindrical medium is higher than a refractive index of the inert medium, and the pulsed laser light undergoes resonance in the cylindrical medium.