Patent ID: 8144391

Claim:
A wavelength converter, comprising: a fundamental wave light source for emitting a fundamental wave having a wavelength of 2000 nm or shorter; a wavelength conversion element composed of a nonlinear optical crystal having a periodical polarization reversal structure and adapted to convert a fundamental wave emitted from the fundamental wave light source into a harmonic wave; and a heating unit for heating the wavelength conversion element, wherein: the period of the polarization reversal structure is so designed that a quasi phase matching temperature of the fundamental wave and the harmonic wave is 40° C. or higher and 80° C. or lower, the heating unit heats the wavelength conversion element to a temperature at which the quasi phase matching is established, and the nonlinear optical crystal is composed of a lithium niobate containing MgO in a molar concentration of 4.2 mol % or more and 4.7 mol % or less and Sc 2 O 3 in a molar concentration of 0.3 mol % or more and 0.9 mol % or less.