| 摘要 |
PROBLEM TO BE SOLVED: To provide a light source using a nonlinear frequency conversion (NLFC) member which overcomes disadvantages of a member having a walk-off when receiving light which should be a non-diffraction limit input beam, and also to attain high output efficiency with such an NLFC member.SOLUTION: A nonlinear frequency conversion (NLFC) member is incorporated in a light source. The light source includes a light emission element which emits a non-diffraction limit input beam, and the NLFC member which causes a walk-off and performs NLFC processing such as secondary higher harmonic generation. An optical member is so formed as to converge the non-diffraction limit input beam at a convergence half-angle determined in the NLFC member. The convergence half-angle in air on a non-walk-off plane of the NLFC member is larger than the convergence half-angle of diffraction limit light. The convergence half-angle may be a multiple obtained by multiplying &egr;×M by the value of the convergence half-angle of the diffraction limit light, &egr; has a value between a lower-limit value which is a larger one between 0.4 and 1/M and an upper-limit value which is 5, and M is the square root of a beam quality coefficient of the non-diffraction limit light. |
