NONLINEAR OPTICAL CRYSTAL FOR GENERATING SECOND HARMONIC GENERATION

摘要

PROBLEM TO BE SOLVED: To enable optimization control relating to double refractive index by generating second harmonic by using a specific nonlinear optical crystal. SOLUTION: The nonlinear optical crystal expressed by the formula GdxY1-xCa4O(BO3)3 (0.25<=X<=0.35) is used and the second harmonic is generated by the same. In such a case, the generation of third harmonic under the non- critical phase matching conditions at room temperature is embodied by the GdxY1-xCa4O(BO3)3 crystal substituted with the Gd portion and the similar thing is made possible even in the second harmonic generation as the nonlinear optical crystal of the constitution described above. The composition ratio X is noticed to be within the range restricted to 0.25 to 0.35. Above all, X=0.28 or the neighborhood thereof is also noticed to be most adequate for the second harmonic generation. For example, the second harmonic is eventually generated surely under the non-critical phase matching conditions at the ratio of Gd near 28% (X=0.28). The crystal is possible to be used at room temperature.