| 摘要 |
PROBLEM TO BE SOLVED: To provide a wavelength conversion element and wavelength conver sion device which are formed by using a nonlinear optical crystal belonging to a point group 3m, such asβ-BaB2O4 and are capable of maintaining the wavelength conversion efficiency at a high level, diminishing the variation of the wavelength conversion efficiently in spite of use of the plural crystals, such asβ-BaB2O4 crystals, and eventually improving the stability of the device. SOLUTION: The phase matching angle of the type 1 of the wavelength conversion element and wavelength conversion device formed by using the nonlinear optical crystal belonging to the point group 3m, such asβ-BaB2O4, is >=45 deg. and theθandϕat the time of phase matching are so set as to approximately satisfy equation I:|sin(3ϕ)|=1, equation II: d22/d31/tanθ/sin (3ϕ)<0 when the angle formed by the surge vector of the incident angle to be phase matched with a +c axis (a direction of plus polarity of the c axis) is defined asθ, the angle formed by the projection of this surge vector to face ab from the a axis asϕcounterclockwise when viewed from the +c direction, d22 as the quadratic nonlinear optical constant of the nonlinear optical crystal and d31 as the quadratic nonlinear optical constant having a specified relation with d22.
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