| CPC H01S 3/08059 (2013.01) [H01S 3/08013 (2013.01); H01S 3/091 (2013.01); H01S 3/0973 (2013.01); H01S 3/0816 (2013.01); H01S 3/094038 (2013.01)] | 13 Claims |

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1. A laser device comprising:
a traveling wave type resonator comprising a first mirror and a second mirror; and
a laser medium disposed between the first mirror and the second mirror, wherein:
the first mirror and the second mirror are disposed such that round-trip light that travels in round trips in the resonator has a focus inside the laser medium;
the laser device is configured such that:
excitation light incident on the resonator is superimposed on the round-trip light at the focus and narrowed to be thinner than the round-trip light,
ZR×α<0.5 is satisfied, where ZR is a Rayleigh length of the excitation light and a is an absorption coefficient of the laser medium with respect to the excitation light, and
a round-trip Gouy phase shift of the resonator has a value excluding 2π×n/m where m is an integer of less than 15 and n is an integer of equal to or less than m.
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