Abstract: A fiber type wavelength converter comprising a cladding made of a thin glass tube an inner wall of which is coated with a coupling agent, and a core which is contained in the cladding and made of a single crystal of methyl 4-hydroxybenzoate, which can convert a fundamental wave to a second harmonic effectively.

Abstract: A device for generating a second harmonic from a laser source is disclosed. The light from the laser passes through an optical fiber in which the second harmonic is generated. The light exiting from the optical fiber has a conical wave surface which is incident upon a collimating lens. Because the collimating lens has a diffraction lattice formed thereon, it is easy and efficient to collimate the second harmonic. It is also possible to decrease the size of the apparatus due to the use of the diffraction lattice formed on the collimator lens. This enable such a device to be particularly useful with a small sized light source such as a semiconductor laser.

Abstract: An arrangement for generating light at a second harmonic of an input light at a fundamental frequency/wavelength. Light at the fundamental frequency/wavelength is generated by a laser and impinges upon an input end of an optical fiber. The optical fiber has a non-linear optical characteristic and generates a second harmonic of the input light. The second harmonic which exits the fiber has an axisymmetrical and conical equiphase wave surface. A collimator lens collimates the second harmonic and parallel light rays are produced on the output side of the lens.

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.