Patent ID: 7653317

Claim:
A semiconductor laser device comprising: a semiconductor laser having a front facet from which an output light is emitted; a first light feedback element arranged at an optical distance L 1 from the front facet on an optical path of the output light, the first light feedback element having a predetermined reflection center wavelength and configured to feed a part of the output light back to the semiconductor laser; and an i-th light feedback element among (n−1) light feedback elements, each arranged at an optical distance Li from the front facet on the optical path of the output light (where i=2 to n, n is a positive integer not less than 2, and Li>L 1 ), the i-th light feedback element each having a reflection center wavelength substantially equal to the reflection center wavelength of the first light feedback element and configured to feed a part of the output light back to the semiconductor laser, wherein L 1 and Li satisfies (( M− 1)+0.01)<( Li/L 1)<( M− 0.01) where M is a positive integer not less than 2, satisfying ( M− 1)<( Li/L 1)≦ M , and an optical distance between adjacent light feedback elements among the (n−1) light feedback elements is not smaller than 50 cm.