Abstract: A fiber-type wavelength converting device comprises a nonlinear optical crystal core; and a glass cladding surrounding the core that produces a second harmonic utilizing Cherenkov radiation. An exit end face of the cladding is flat, and an exit end face of the core has asperities. The exit end face of the core is formed inside with respect to the exit end face of the cladding, and particles may be filled in a recess portion composed of a bottom surface of the exit end face of the core and side surface of an inner wall of the cladding. The cladding has an outer diameter of at least 1 mm to prevent breakage of device upon polishing and grinding. A thin film may be formed on an input end face of the device.

Abstract: A fiber wavelength modulator device which emits a secondary harmonic component by Cerenkov radiation, including a core being a single crystal of a non-linear optical material and a cladding being composed of glass, wherein the relative difference between the core and the cladding has a refraction index with respect to an incident beam, of at lesat 0.015.