Optical waveguides – With optical coupler – Particular coupling structure
Patent
1996-10-04
1998-11-03
Ngo, John
Optical waveguides
With optical coupler
Particular coupling structure
385 24, 385 45, 385 17, 385 9, 385 41, 385 14, 385 2, G02B 610
Patent
active
058321551
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
a) Field of the Invention
The invention concerns a junction splitter used for the spatial combination or splitting of light of different wavelengths or different wavelength ranges from a comparably large wavelength spectrum. If required, this wideband junction splitter is used to switch, deviate, or modulate light.
The invention also provides for applications of this wideband junction splitter. The single-mode channel waveguides used for the wideband junction splitter are single-mode integrated-optical wideband channel waveguides or white light channel waveguides described in the patent application "Channel Waveguide and Applications" submitted on the same day.
The invention is also related to the patent application "Colour Image Generation Systems and Applications".
For the purposes of this document, light refers to visible and invisible (infrared and ultraviolet) electromagnetic radiation, in particular however discrete wavelengths or wavelength ranges of visible radiation in the wavelength spectrum from 400 nm to 760 nm. The designation "channel waveguide" is applied to waveguides based on the principle of the total reflection of light, caused by an increase in the refractive index within the waveguiding region in relation to the surrounding medium.
b) Description of Related Art
Junction splitters for a bandwidth less than 95 nm (value given applies to short-wave visible light) are known. The combination of discrete channel waveguides is effected for the purpose of combining light according to the basically known principle of two-mode interference by: X-couplers, directional couplers, three-guide couplers, or BOA (see W. Karthe, R. Muller, Integrierte Optik (Integrated Optics), Akademische Verlagsgesellschaft Geest & Portig K.-G., Leipzig, 1991 and A. Neyer: "Integriert-Optische Komponenten fur die Optische Nachrichtentechnik" (Integrated-Optical Components for Optical Communications Technology), habilitation thesis, University of Dortmund 1990).
BOA is a French language designation (bifurcation optique active) for a group of integrated-optical devices (see: M. Papuchon, A. Roy, D. B. Ostrowsky, "Electrically active optical bifurcation: BOA"; Appl. Phys. Lett., Vol. 31 (1977) pp. 266-267).
The efficiency of junction-splitting--in addition to the simultaneous requirement for efficient modulation and/or switching of the light--is dependent on the channel waveguides that provide the inputs and outputs of the junction splitter being in single-mode. The known channel waveguides for wavelength ranges with a bandwidth greater than approximately 130 nm (value given applies to short-wave visible light) are not single-mode.
Different light wavelengths require different values of the characteristic channel waveguide parameters such as the refractive index of the substrate, refractive index of the superstrate, refractive index or one- or two-dimensional refractive index profile of the channel waveguide, cross-sectional shape (e.g. width and depth), and channel waveguide position in or on the substrate. In general, this requires the use of different channel waveguides for different wavelengths of the guided light.
In the case of a junction splitting on the basis of known channel waveguides, e.g. the titanium-indiffused channel waveguide in LiNbO.sub.3, the usable wavelength range reduces by approximately 35 nm, when compared against the wavelength range of the associated single-mode channel waveguide, as in junction splitters based on two-mode interference such as Y-junction couplers, directional couplers, three-guide couplers, X-couplers, or BOA, the oscillation build-up of the second mode in lateral direction in the junction or splitting area must be avoided. This is the precondition for a constant splitting ratio of the light transmission performance for junction splitter operation across the entire usable wavelength range.
To achieve efficient junction splitting of light from a wavelength range greater 95 nm, it is thus necessary to use one and the same single-mode channel waveguide
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"Integrierte Optik", Karthe, Muller & Jena, Akademische Verlagsgesellschaft Geest & Portig K.-G. Leipzig, 1991.
Fabrication and Characterization of Optical Waveguides in KtiOPO.sub.4, Bierlein, Ferretti, Brixner & Hsu, Appl. Phys. Lett. 50(18), Mar. 4, 1987, pp. 1216-1218.
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Proceedings of the Spie, vol. 2213, Jan. 1994, pp. 152-163, Article "Fabrication and Characterization of Singlemode Channel Waveguides and Modulators in KT10P04 for the Short Visible Wavelength Region"/ Rottschalk, et al.
Groeber Volker
Rasch Andreas
Rottschalk Matthias
Ruske Jens-Peter
LDT Gmb&H Co. Laser-Display-Technologie KG
Ngo John
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