Optical wavelength converter device

DETAILED DESCRIPTION In view of the aforesaid drawbacks of the conventional optical wavelength converter devices, it is an object of the present invention to provide an optical wavelength converter device capable of preventing the phase of a second harmonic from being disturbed, capable of preventing the second harmonic from being absorbed by a core, and also capable of producing a second harmonic in the form of a high intentity short wave.
According to the present invention, an optical wavelength converter device of the optical fiber type comprising a core made of a nonlinear optical material and a cladding surrounding the core, for converting a fundamental applied to an end of the core to a second harmonic and radiating the second harmonic into the cladding to eliminate interference between waves traveling in a guided mode in which the fundamental is guided through the core and waves traveling in a radiation mode in which the second harmonic is radiated into the cladding, the cladding having a diameter of at least 500 .
mu.
m.
The phase of a second harmonic is considered to be disturbed for any of the following reasons: (1) As shown in FIG.
5(a) of the accompanying drawings, a second harmonic 55' travels toward an end of the optical wavelength converter device while repeatedly undergoing total reflection by outer surfaces 52a of a cladding 52 surrounding a core 51.
Due to the difference between the refractive indexes of the cladding 52 and the core 51, the second harmonic 55' is subjected to Fresnel reflection, as indicated by the dotted lines, and the second harmonic 55' that has passed through the core 51 and the second harmonic 55' that has undergone the Fresnel reflection become out of phase with each other.
(2) Where the refractive index of the cladding 52 with respect to the second harmonic is higher than that of the core 51, the second harmonic 55' is subjected to total reflection at the boundary between the core 51 and the cladding 52, as indicated by the dotted line in FIG.
5(b), which results in disturbance of the phase