Optical: systems and elements – Optical frequency converter – Dielectric optical waveguide type
Reexamination Certificate
1999-03-18
2001-05-22
Lee, John D. (Department: 2874)
Optical: systems and elements
Optical frequency converter
Dielectric optical waveguide type
C385S122000, C385S141000
Reexamination Certificate
active
06236494
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a wavelength converting device for obtaining, for example, a second order harmonic by converting the wavelength of a light beam such as a laser, and more specifically to a wavelength converting device having a substrate composed of spinel and a waveguide formed of a KNbO
3
layer and a method of fabricating the wavelength converting device.
2. Description of the Related Art
A wavelength converting device has a function of radiating a second order harmonic of a laser. This is preferably utilized for obtaining a laser having a shorter wavelength. A typical wavelength converting device has: a substrate composed of spinel (for example, MgO.Al
2
O
3
); a waveguide formed of a KNbO
3
layer, which is formed on the substrate by crystal growth; an electrode layer formed on the surface of the KNbO
3
layer; and a stripe-shaped TiO
2
layer which is used to shut the light therein and which is formed on the surface of the KNbO
3
layer. The KNbO
3
layer has characteristics that a nonlinear optical constant is large and that a light damage resistance is high. Therefore, this type of the wave converting device enables high efficient wavelength conversion and has a long life.
However, this type of wave converting device has a problem that deformation occurs in the KNbO
3
layer because the lattice constant of the KNbO
3
layer is mismatched with that of the spinel (namely, a multiple of the lattice constant of KNbO
3
layer is mismatched with that of the spinel). This causes a loss to propagation of a light.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a wavelength converting device and a method of fabricating a wavelength converting device, which can reduce deformation in a waveguide layer and achieve an optimum wavelength conversion if the lattice constant of a substrate and the lattice constant of the waveguide layer are mismatched with each other.
According to one aspect of the present invention, a wavelength converting device including: a waveguide layer for guiding the light; a substrate having a lattice constant different from a lattice constant of the waveguide layer; and a buffer layer which is disposed between the waveguide layer and the substrate and which has a lattice constant between the lattice constant of the waveguide and the lattice constant of the substrate. Since the buffer layer is located between the substrate and the waveguide layer, a mismatch of the lattice constants between the substrate and the waveguide layer can be eased. Therefore, the influence of the mismatch of the lattice constants between the substrate and the waveguide layer on the waveguide layer can be reduced, thereby reducing the deformation in the waveguide layer.
In the case where the waveguide layer comprises KNbO
3
, the substrate comprises spinel, the buffer layer may comprise K
(1−x)
Rb
x
NbO
3
. In this case, it is preferably that the mixing rate of Rb in the K
(1−x)
Rb
x
NbO
3
in the buffer layer is gradually varied between a surface of the buffer layer touching the substrate
1
and a surface of the buffer layer touching the waveguide layer. Instead of K
(1−x)
Rb
x
NbO
3
layer, K
(1−x)
Cs
x
NbO
3
layer may be uses as a buffer layer.
The present invention provides a method of fabricating this wavelength converting device. The method including the processes of: preparing the substrate; forming the buffer layer on the substrate by inducing crystal growth; and forming the waveguide layer on the formed buffer layer by inducing crystal growth.
The nature, utility, and further feature of this invention will be more clearly apparent from the following detailed description with respect to preferred embodiments of the invention when read in conjunction with the accompanying drawings briefly described below.
REFERENCES:
patent: 5581396 (1996-12-01), Kubota et al.
patent: 6163397 (2000-12-01), Onoe et al.
patent: 6-67235 (1994-03-01), None
Chikuma Kiyofumi
Onoe Atsushi
Yoshida Ayako
Lee John D.
Pioneer Electronic Corporation
Young & Thompson
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