Optical waveguides – Temporal optical modulation within an optical waveguide – Electro-optic
Patent
1995-03-07
1997-06-10
Bovernick, Rodney B.
Optical waveguides
Temporal optical modulation within an optical waveguide
Electro-optic
385 13, G02F 1035
Patent
active
056384688
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to an optical modulation system for modulating a light beam transmitted through an optical waveguide by applying an external electric field.
BACKGROUND ART
There is known a conventional optical modulation system comprising a light source, an optical device supplied with a light beam from the light source, and an electric field applying device for applying an electric field to the optical device. The optical device comprises a substrate, an incident optical waveguide formed on the substrate for receiving the light beam incident thereto, two phase-shift optical waveguides formed on the substrate to be branched from the incident optical waveguide for varying a phase of a transmitted light beam in response to an electric field intensity, and an outgoing optical waveguide formed on the substrate to join the phase-shift optical waveguides.
In the conventional optical modulation system, however, a phase difference is caused between the branched optical waveguides even if the intensity of the applied electric field is equal to zero, depending upon manufacturing conditions of the optical waveguides. This results in fluctuation of a ratio of the variation of light intensity relative to the variation of the applied electric field, namely, fluctuation of an optical modulation efficiency.
In addition, the conventional optical modulation system is disadvantageous in that the optical device tends to deteriorate when the magnitude of the applied electric field is great.
It is an object of this invention to provide an optical modulation system capable of readily adjusting a phase difference when the intensity of an applied electric field is equal to zero.
It is an object of this invention to provide an optical modulation device capable of avoiding deterioration of an optical device even if the magnitude of an applied electric field is great.
DISCLOSURE OF THE INVENTION
This invention is characterized by provision of a substrate, an incident optical waveguide formed on the substrate for receiving a light beam incident thereto, two phase-shift optical waveguides formed on the substrate to be branched from the incident optical waveguide for varying an intensity of a transmitted light beam in response to a phase of an electric field, and an outgoing optical waveguide formed on the substrate to join the phase-shift optical waveguides, at least one of the phase-shift optical waveguides having a reversely polarized portion reversely polarized.
This invention is also characterized by provision of a substrate, an optical waveguide formed on the substrate for varying an intensity of a transmitted light beam in response to an intensity of an electric field, and a light transmission film formed at one or a plurality of areas on the optical waveguide.
This invention is also characterized by a buffer layer formed at a part on or in the vicinity of the phase-shift optical waveguides.
This invention is also characterized by a buffer layer formed at a part on or in the vicinity of the phase-shift optical waveguides, and a transparent substance film formed on a part or a whole of a portion without the buffer layer for imparting a stress on the phase-shift optical waveguides.
This invention is also characterized by a stress imparting member for imparting a stress to a part of one of the phase-shift optical waveguides.
This invention is also characterized by a light irradiation unit for irradiating a light beam onto a part or a whole of one of the phase-shift optical waveguides.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a front view of an optical modulation system according to this invention.
FIG. 2 is a front view of another embodiment of this invention.
FIG. 3 is a view for describing a characteristic of the embodiment in FIG. 2.
FIG. 4 is a view for describing another characteristic of the embodiment in FIG. 2.
FIG. 5 is a perspective view of another embodiment of this invention.
FIG. 6 is a perspective view of another embodiment of this invention.
FIG. 7 is a view for describing a characte
REFERENCES:
patent: 5091983 (1992-02-01), Lukosz
patent: 5267336 (1993-11-01), Sriram et al.
patent: 5333217 (1994-07-01), Kossat
IEEE Photonics Technology Letters, Jun. 1991, USA, vol. 3, No. 6, ISSN 1041-1135, pp. 510-512, XP 000227339 C.H. Bulmer et al, "Phase Tuning By Laser Ablation of LiNbO.sub.3 Interferometric modulators to optimum linearity".
Muramatsu Ryoji
Takeda Tsugio
Tanabe Takanobu
Tokano Yuichi
Bovernick Rodney B.
Tokin Corporation
Wise Robert E.
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