Optical waveguides – Having particular optical characteristic modifying chemical... – Of waveguide core
Patent
1997-03-20
1999-03-09
Lee, John D.
Optical waveguides
Having particular optical characteristic modifying chemical...
Of waveguide core
385143, 385125, G02B 620
Patent
active
058812008
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an optical fibre and has particular but not exclusive application to use as an optical amplifier.
2. Related Art
It is known that erbium doped fibres can be used as optical amplifiers. However, they suffer from a number of disadvantages. For example, a long length of fibre is required in order to achieve a significant level of amplification, e.g. 10 m. Also, erbium is a toxic substance so manufacture of the doped fibre is complex and requires strict pollution control measures.
Recently, it has been shown that very small particles, fabricated on the nanometre scale, give rise to specific optical effects, such as electroluminescence. A review is given in Colloidal Semi-conductor Q-Particles; Chemistry in the Transition Region Between Solid State and Molecules, M. Weller: Angew, Chem. Int. Ed. Engl. 1993, 32,41-53. These nanometre scale particles are known as quantum dots.
A laser making use of quantum dots is described in U.S. Pat. No. 5,260,957. In this arrangement, a host material such as PMMA contains quantum dots. The laser may be in the form of a channel waveguide device, the host material being arranged in a cavity formed in a channel machined in a substrate, the substrate having a lower refractive index than the host. The laser is pumped by an external light source in order to provide a laser output. The use of polymeric material is said to be advantageous.
An optical fibre with non-linear optical characteristics is known from JP-A-4-195028, in which the interior of a tubular glass sheath is coated with materials that, on subsequent heating, form particulate material disposed in a glass core of the fibre.
SUMMARY OF THE INVENTION
The present invention is concerned with the production of an optical fibre with improved amplification or wavelength conversion characteristics.
In accordance with the present invention, there is provided an optical fibre with a colloid of quantum dots therein.
The fibre may include a core and a cladding, with the colloid of quantum dots forming at least part of the core.
The colloid of quantum dots may include a non-vitreous support medium in which the dots are dispersed, e.g dichlorobenzene, toluene, benzene, nitrobenzene, pyridene or carbontetrachloride.
The dot density in the medium and the diameter distribution for the dots are selected depending on the application of the fibre. Similarly, the materials from which the dots are made are selected depending on the intended use. For example, when used as an optical amplifier, the quantum dots may comprise lead sulphide (PbS) with a diameter range of 5-10 nm.
The fibre according to the invention has particular application as an amplifier, when pumped by an external source, so that input light, e.g. light pulses, can be amplified. The arrangement may be similar to that used for a conventional erbium doped fibre, but with the advantage that the amplification is more efficient and so a much shorter length of fibre can be used. The fibre however has other uses, e.g. as a wavelength converter.
BRIEF DESCRIPTION OF THE DRAWINGS
In order that the invention may be more fully understood, an embodiment thereof and a method of making the same will now be described by way of example with reference to the accompanying drawings, in which:
FIG. 1 is a schematic perspective view of an optical fibre in accordance with the invention;
FIG. 2 is a transverse cross section of the fibre shown in FIG. 1;
FIG. 3 shows a method of making the fibre shown in FIG. 1; and
FIG. 4 illustrates the fibre, used in an optical amplifier.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS
Referring to FIG. 1, this shows an example of optical fibre in accordance with the invention which consists of a tubular glass sheath 1 that has an elongated central opening 2 running the length thereof. Such a hollow fibre can be made and filled with a liquid in the manner demonstrated by Kashyap and Finlayson in Optics Letters 17 pp 405-407 (1992). The central opening 2 is filled with a collo
REFERENCES:
patent: 5260957 (1993-11-01), Hakimi et al.
patent: 5452123 (1995-09-01), Asher et al.
Tauber et al, Optical Fiber Communication Conference '92 Technical Digest, vol. 5, 2 Feb. 1992, San Jose, US, p. 71.
DATABASE WPI Section Ch, Week 9235, Derwent Publications Ltd., London GB, Class L01, AN 92-287166 & JP-A-04 195 028 (Furukawa Electric Co. Ltd.), 15 Jul. 1992.
Patent Abstracts of Japan, vol. 95, No. 1, 28 Feb. 1995 & JP A 06 301071 (Mitsui Toatsu Chem.) 28 Oct. 1994.
Mews et al., "Preparation, Characterization, and Photophysics of the Quantum Dot Quantum Well System DdS/HgS/CdS", Journal of Physical Chemistry, vol. 98, No. 3, 20 Jan. 1994, USA, pp. 934-941.
Rajh et al, "Syntheisis and Characterization of Surface-Modified Colloidal CdTe Quantum Dots", Journal of Physical Chemistry, vol. 97, No. 46, 1993, USA, pp. 11999-12003.
Schwerzel et al, "Nonlinear Optical Properties of Colloidal Quantum-cot Composite Materials with Tailored Organic Coatings", Proc. of the SPIE, vol. 1337, 1990, pp. 132-141 No month.
Ghatak, "The Termoelectric Power in Fiber Optic and Laser Materials Under Cross Field Configuration", Fiber Optic and Laser Sensors IX, Boston, MA, USA, 3-5 Sep. 1991, vol. 1584, ISSN 0277-786X, Proceedings of Optical Engineering, 1991, USA, pp. 435-447.
British Telecommunications public limited company
Kang Ellen E.
Lee John D.
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