a solid - state laser oscillator comprising solid - state laser rods disposed coaxially in series with each other , radiating light when excited , and amplifying the light through stimulated emission . a solid - state laser rod exciting device excites any number of solid - state laser rods with a 90 ° optical rotator disposed coaxially and arranged between the rods . the rotator rotates a component of the light generated in the axial direction while heat lens compensating devices are disposed coaxially with the solid - state laser rods . a reflecting device and a partial reflection device are disposed coaxially and arranged , outside of the solid - state laser rods and heat lens compensating devices , for propagating the axially generated component of the light . an exciting source driving device drives the exciting sources included in the solid - state laser rod exciting device .