Wavelength converter, an image display device and a processing device

Wavelength conversion apparatus, an infrared light source (1) for emitting a fundamental wave having a wavelength of 2000nm or less, made of a nonlinear optical crystal having a periodic polarization inversion structure, and is emitted from the infrared light source (1) includes a wavelength conversion element for converting the fundamental wave into the harmonic (3), and a heater (4) for heating the wavelength conversion element (3). Period of the domain inversion structure, temperatures the fundamental wave and the harmonic wave is quasi-phase matching are designed to be above 40 ° C., a heater (4), the wavelength conversion element to a temperature quasi phase matching is established ( 3) heating the nonlinear optical crystal is mainly Mg, an in, Zn and lithium niobate or lithium tantalate having at least one of additives Sc. Thus, it is possible to suppress the optical damage, it is possible to reduce absorption of visible light by ultraviolet light.