Title of Invention

AN INTEGRATED OPTICAL DEVICE

Abstract An integrated optical device (5a,e) providing first (l0a-e) and second (15a,e) devices optically coupled one to the other and formed in first and second different material systems and on different substrates, one or both of the first and second devices having a Quantum Well Intermixed (QWI) region (20a-e) at or adjacent a coupling region (21a,e) between the first and second devices and said coupling region provides means (30b-f) for mode matching between the first and second devices.
Full Text FIELD OF INVENTION
This invention relates to an improved integrated optical device or optoelectronic device, and particularly to hybrid integration of devices formed in different material systems. For example, hybrid integration of III-V semiconductor devices with passive waveguide structures.
BACKGROUND TO INVENTION
Hybrid integration of III-v semiconductor components with passive waveguides is of increasing importance as a method of increasing the functionality of integrated optical and photonic systems. Applications include.-optical communication systems, optical sensing applications, and optical data processing.
A fundamental problem in hybrid integration is that the semiconductor element has a higher refractive index than the passive waveguide. in the case of a III-V semiconductor component integrated on a planar Silica (SiO2) platform, the refractive indices are typically around 3.6 for the semiconductor and 1.5 for the Silica. This refractive index difference causes a number of problems, eg there is a. high reflection coefficient at the interface between the two devices, and the mode size in each device is different. Both of these effects result in a loss in. optical power and reduced coupling efficiency between the two devices, and scattering of light, and undesirable reflections.
It is an object of the present invention to obviate or at least mitigate one or more of the aforementioned problems, in the prior art
Further objects of various embodiments of the present invention include .-
enablement of hybrid integration to be carried out, while ensuring good mode matching between active and
passive sections,-
ease of manufacture;
low loss coupling between active and passive sections.
SUMMARY OF INVENTION
According to a first aspect of the present invention there is provided an integrated optical device providing first and second devices optically coupled one to the other and formed in first and second different material systems, at least one of the first or second devices having a Quantum well .Intermixed (QWI) region at or adjacent a coupling region between the first and second devices.
Quantum Well Intermixing (QWI) permits a postgrowth modification to the absorption edge of Multiple-Quantum Well (MQW) material, and therefore provides a flexible.
reliable, simple, and low-cost approach compared to competing integration schemes such as selective area epitaxy or selective etching and regrowth.
Quantum Well Intermixing (QWI) provides a means of
tuning an absorption band edge controllably in Quantum Well
(QW) structures and may be utilized to fabricate low-loss
optical interconnects between monolithically integrated
optical devices or integrated optoelectronic devices.
The first material system may be a III-V semiconductor material system. The III-V semiconductor material may be selected from or include one or more of: Gallium Arsenide (GaAs), Aluminium Gallium Arsenide (AlGaAs), Indium Phosphide (InP) , Gallium Arsenide Phosphide (GaAsP), Aluminium Gallium Arsenide Phosphide (AlGaAsP), Indium Gallium Arsenide Phosphide (InGaAsP), or the like.
The second material system may be a non III-V
semiconductor material. The second material system may be
selected from. Silica (SiO,) , Silicon (Si) , Lithium Niobate
(LiNbOJ , a polymer, a glass, or the like any of which may
be doped with optically active material.
The first device may be or include an active device component, such as a laser diode, light emittincr diode
(LED), optical modulator, optical amplifier, optical switch, or switching element, optical detector (eg photodiode), or the like. The first device may also include a passive device compound such as a passive waveguide.
The second device may be or include a passive component such as a passive waveguide.
Preferably, the coupling region provides means for at least substantially mode matching between the first and second devices.
in one arrangement the first device provides the Quantum Well (QW)intermixed region.
In the one arrangement the mode matching means may comprise a waveguide provided in the first device which waveguide may be a "tapered" waveguide providing a linear change in width, a non-linear change in width, and/or a "periodic" or "a-periodic" segmentation.
Preferably, the coupling region provides anti-reflection means at or near an interface between the first and second devices.
The anti-reflection means may comprise or include an anti-reflection coating on a facet of the first device provided at the interface between the first and second devices.
The anti-reflection means may also comprise or include facets of the first and second devices provided at the interface between the first and second devices, the facets being formed at an (acute) angle to an intended direction of optical transmission. The facets may therefore be referred to as "angled facets".
In a preferred embodiment a first waveguide section m the first device and preferably also a second waveguide section in the second device is/are bent.
The integrated optical device may be adapted to operate m a wavelength region of GOO to I300nm or of 1200 to 1700 ran.
According to a second aspect of the present invention, there is provided an integrated optical circuit,
optoelectronic integrated circuit, or photonic integrated circuit including at least one integrated optical device according to the first aspect of the present invention
According to a third aspect of the present invention there is provided an apparatus including at least one integrated optical device, the at least one integrated optical device providing first and second devices optically coupled one to the other and formed in first and second different material systems, one of the first or second devices having a Quantum Well Intermixed (QWI) region at or adjacent a coupling region between the first and second devices.
According to a fourth aspect of the present invention there is provided a method of providing an integrated optical device having hybrid integration of first and second devices formed in first and second different material systems comprising:
providing one of the first or second devices with a Quantum Well Intermixed (QWI) region at or adjacent a coupling region between the first and second devices.
The Quantum Well Intermixed (QWI) region may be formed from a number of techniques, but preferably by a universal damage induced technique, Impurity Free Vacancy Diffusion (IFVD).
In a preferred embodiment, the Quantum Well Intermixed
(QWI) region may be formed in the first device by
intermixing a Quantum Well(s) (QW) in a core optical
guiding layer of the first device, eg by Impurity Free
Vacancy Diffusion (IFVD)
When performing IFVD upon a top cap layer of the a III-V semiconductor material comprising the first device is deposited a dielectric, eg SiO; layer or film. Subsequent rapid thermal annealing of the semiconductor material causes bonds to break within the semiconductor alloy, eg Gallium ions or atoms which are susceptible to Silica (SiCL) , to dissolve into the Silica sc as to leave vacancies in the cap layer. The vacancies then diffuse through the
semiconductor material inducing layer intermixing, eg in
the Quantum Well(s) (QW)
IFVD has been reported m "Quantitative Model for the Kinetics of Compositional Intermixing in GaAs - AlGaAs Quantum - Confined Heterostructures", by Helmy et al, IEEE
Journal of Selected Topics m Quantum Electronics, Vol 4, No 4, July /Augustl998, pp 653 - 660, the content of which is incorporated herein by reference.
According to a fifth aspect of the present invention there is provided a first device according to the first aspect of the present invention.
BRIEF DESCRIPTION OF DRAWINGS
Embodiments of the present invention will now be described, by way of example only, and with reference to the accompanying diagrams, which are:
Figure 1(a) a schematic plan view of a first
semiconductor chip integrated with a passive photonic integrated circuit (PIC) according to a first embodiment of the present invention;
Figure 1(b)-(d) schematic plan views of second, third
and fourth semiconductor chips integratable with a passive photonic integrated circuit (PIC) similar to or the same as that of Figure 1(a) according to the present invention;
Figure 2 (a) a schematic plan view of a fifth
semiconductor chip according to the present invention,-
Figure 2 (b) a schematic plan view of the fifth
semiconductor chip of Figure 2(a) integrated with a passive photonic
integrated circuit (PIC) according to a fifth embodiment of the present
invention;
Figure 3 a schematic cross-sectional end view
showing a possible layer structure of a semiconductor chip according to a sixth embodiment of the present invention;
Figure 4 a schematic perspective view from one
end, above and to one side of the semiconductor chip of Figure 3 ,-
Figure 5 a schematic perspective view from one
end, above and to one side of a semiconductor chip according to a seventh embodiment of the present invention.
DETAILED DESCRIPTION OF DRAWINGS
Referring initially to Figure 1 (a) there is illustrated an integrated optical device, generally designated 5a, according to a first embodiment of the present invention and providing the first and second devices 10a, 15a respectively, the first and second devices 10a, 15a being optical coupled one to the other and formed in first and second dis-similar material systems, at least one of the first or second devices 10a, 15a having a Quantum Well Intermixed (QWI) region 20a at or adjacent a coupling region 21a between the first and second devices 10a,15a.
In this embodiment the first materials system is a III-V semiconductor material system based on either Gallium Arsenide (GaAs) or Indium Phosphide (InP). For example the III-V semiconductor material may be selected or include one or more of: Gallium Arsenide (GaAs), Aluminium Gallium
Arsenide (AlGaAs) , and Indium Phosphide (InP) , Gallium Arsenide Phosphide (GaAsP), Aluminium Gallium Arsenide Phosphide (AlGaAsP) , Indium Gallium Arsenide Phosphide (InGaAsP), or the like The integrated optical device 5a may therefore be adapted to operate in the so-called "short" wavelength region of 600 to 13 00nm, or the so-called "long" wavelength region of 1200 to 1700 nm.
The second material system is a non III-V semiconductor material and can be selected from Silica (SiO_) , Silicon (Si) , Lithium Niobate (LiNbo?) , a polymer, glass or the like.
The first device 10a comprises an active device component 22a, selected from a laser diode, light emitting diode (LED), optical modulator, optical amplifier, optical switching element, optical detector (eg photodiode) , or the like. The active device component 22a is spaced from the Quantum Well Intermixed (QWI) region 2 0a, the active device component 22a, and passive QWI region 20a being m optical communication one with the other via a waveguide 23a such as a ridge waveguide.
The second device 15a in this embodiment includes a passive device component m the form of a passive waveguide 16a.
The coupling region 21a provides anti-reflection means at or near an interface between the first and second devices 10a, 15a. The anti-reflection means comprise anti-reflection coating 25a on an end facet on first device 10a provided at the interface between the first and second devices 10a, 15a.
In a modification the anti-reflection means may also comprise facets of the first and second devices 10a, 15a provided at the interface between the first and second devices 10a, 15a, the facets being formed at an acute angle to the intended direction of the optical transmission along waveguides 23a, 16a. In such a modification the facets may be referred to as "angled facets".
Referring now to Figure 1 (b) there is illustrated a
second embodiment of a first device 10b comprising part of an optically integrated device according to the present invention, like parts of the device 10b being identified by the same numerals as those for the first embodiment, but suffixed "b". In this second embodiment the waveguide 23b includes a curved portion 3 0b s'o as to improve optical coupling between the first device 10b and a second device (not shown), by reduction of reflections at the interface between the first device 10b and the second device.
Referring now to Figure 1(c), there is illustrated a third embodiment of a first device, generally designated 10c, comprising part of an optically integrated device according to an embodiment of a present invention. The device 10(c) is similar to the device 10a of the first embodiment, and like parts are identified by like numerals, but suffixed "c". However, as can be seen from Figure 1 (c) , the waveguide 23c includes at an end adjacent the coupling region to the second device (not shown) a tapered region 30c which, in use, causes an optical mode "M" transmitted along the waveguide 23c to expand as it traverses the optical waveguide 23c and is output from the first device 10c from the tapered region 30c. The converse of course applies for optical coupling to the first device 10c from the second device (not shown).
Referring now to Figure 1(d), there is shown a fourth embodiment of a first device lOd comprising part of an optically integrated device according to an embodiment of the present invention. The first device lOd is substantially similar to the device 10a of the first embodiment, like parts being identified by like numerals but suffixed "d" . However, m the first device lOd, the waveguide 23d includes at an end adjacent a coupling region to a second device (not shown) a curved and tapered region 30b. The first device lOd therefore combines the features of the embodiments of Figures 1(b) and (c).
As will be appreciated, to ele :trically control the first devices lOa-lOd, an electrical contact (metalisation)
will be fabricated en a surface of the waveguide 23a-23d, while a further electrical contact (metalisation) will be provided on an opposing surface of the device 10a-10b
It will be appreciated that the modifications shown in the second, third and fourth embodiments 10b, 10c, lOd, seek to improve optical coupling between the first device 10b, 10c, lOd, and a second device (not shown).
It will also be appreciated that the intermixed region 20a to 20b acts to prevent, or at least reduce, optical absorption m the intermixed region 20a-20d adjacent to the coupling region 21a-21d This is particularly so in the curved tapered waveguide section 30b.
It will further be appreciated that although herein above the waveguide sections 3 0c and 3 0d have been referred to as "tapered" regions, the optical mode transmitted therein towards an end of the first device 10c to lOd adjacent to second device (not shown) actually flares.
Referring now to Figures 2 (a) and (b) , there is illustrated an integrated optical device general designated 5e, according to a fifth embodiment of the present invention. The device 5e provides first and second devices lOe, 15e optical coupled one to the other and formed in first and second different material systems, the first device lOe having a Quantum Well Intermixed (QWI) region 20e adjacent a coupling region 21e between the first and second device lOe, 15e. As can be seen from Figures 2(a) and (b) a waveguide 23e of the first device lOe comprises a tapered curved region 3 0e adjacent a coupling region 21e between the first and second devices lOe, 15e. Further, an anti-reflection coating 25e is provided within the coupling region 21e on an end facet of the first device lOe. Also, a passive waveguide 16e of the second device 15e is complementarily curved to the portion 3 0e so as to also assist in optical coupling between the first and second devices lOe, 15e.
Referring now to Figures 3 and 4, there is illustrated a sixth embodiment of a first device generally designated

lOf according to the present invention. Like parts of the device lOf are identified by the same numerals as for the device 10a of the first embodiment of Figure 1 (a) , but suffixed "f".
The device lOf comprises an GaAs substrate 5Of, upon which are grown a number of epitaxial layers by known growth technique such as Molecular Beam Epitaxy (MBE) or Metal Organic Chemical Vapour Deposition (MOCVD). The layers comprise a first 0. 5µm to 1µm n-doped Al0.50Ga0 50As layer 55f, a second 5µm n-doped Al0 40Ga0 60As layer 60f, a third 0.5µm substantially intrinsic Al0 20Ga0 80As core layer, including a l0nm GaAs Quantum Well (QW) , 70f as grown. On the core layer 65f is grown a 1µm p-doped Al0 40Ga0 60As layer 75f, and finally on that layer is grown a p+ doped GaAs capping contact layer 80f As can be seen from Figure 3, a ridge waveguide 23f is formed in the layers 75f,80f by known photolithographic techniques. Further in this embodiment, a second broader ridge or mesa 35f is also formed in the layers 65f and 60f. Thus the ridge waveguide 23 f comprises a primary waveguide while the mesa 35f comprises a secondary waveguide. The device lOf also includes a tapered region 30f on the waveguide 23f. The device lOf, therefore, acts as a mode converter converting a mode from the device lOf coupled to a second device (not shown), or a mode transmitted from the second device to the first device lOf.
As can be seen from Figure 3, contact metallisations 40f and 45f may be provided on a top of ridge 23f and an opposing surface of the substrate 50f. Further, as can be seen from Figure 4, the device lOf includes a Quantum Well Intermixed (QWI) region 20f adjacent to the end of the device corresponding to the tapered region 30f.
In this embodiment the Quantum Well Intermixed (QWI) region 20a is formed in the first device lOf by intermixing the Quantum Well 70f in the layer 60f within the region 20f by Impurity Free Vacancy Diffusion (IFVD). When performing
IFVD upon a top cap layer 80f of the III-V semiconductor material comprising the first device lOf, there is deposited a dielectric, eg Silica (Silo2) , layer of film. Subsequent rapid thermal healing of the semiconductor material causes bonds to break within the semiconductor alloy and eg Gallium ions or atoms - which are susceptible to Silica (SiO_) - to dissolve into the Silica so as to leave vacancies in the cap layer 80f. The vacancies then diffuse through the semiconductor material inducing layer intermixing, eg in the Quantum Well 70f.
Referring now to Figure 5 and to Table 1, there is illustrated a seventh embodiment of a first device generally designated 10g, for use in an optically integrated device according to the present invention. In this sixth embodiment, the first device lOg is fabricated in Indium Gallium Arsenide Phosphide (In In; Gav Asy P1-y) . The layer structure, grown on an Indium Phosphide (InP) substrate 50g, is shown m Table 1 below.
TABLE 1
(Table Removed)
Q = Quaternary, eg Ql.l - quaternary with 1.1µm bandgap
As can be seen from Figure 5, the first device lOg includes an active waveguide 2 3g and adjacent to coupling region to a second device (not shown) a tapered region 30g. The waveguide 23g comprises a primary waveguide of the first device lOg, while a further ridge or mesa 35g formed on the device lOg comprises a secondary waveguide. In use, the optical radiation generated within or transmitted from the waveguide 23g towards the tapered region 3 0g as an optical mode, is caused upon transmission through region
3 0g from primary optical guiding layer 65g into layer 60g for optical coupling to second device (not shown).
The first devices 5f,5g illustrate a design of regrowth-free tapered waveguide coupler. The small rib waveguide 23f,23g is located on top of a thick lower cladding layer 60f that is partially etched to form mesa waveguide 35f,35g. When the small rib 23f,23g is sufficiently wide, the fundamental optical mode is confined to the small 23f,23g/ and there is a high confinement of light within the undoped waveguide core layer 65f, (which itself contains the active Quantum Well layers 75f or intermixed region 20f,20g) At the other extreme, when the small rib 23f,23g is sufficiently narrow, the fundamental mode expands to fill the larger mesa waveguide 35f,35g. This behaviour is a consequence of the design of the waveguide layers. The thicknesses and compositions of the Quantum Well layers at the top of the mesa 35f,35g, and extending under the small rib 23f,23g are such as to prevent guiding of light within these layers if the upper layers comprising the small rib 23f,23g are etched away. The resulting waveguide allows separate optimisation of the optical mode properties of the rib 23f,23g and mesa 35f,35g waveguides at the two extremes of rib width. At large rib widths high-performance device action (such as optical amplification, optical detection, electro-absorptive or electro-refractive modulation) can be achieved. At small rib widths the dimensions of the large mesa 35f,35g and thickness of the lower cladding materials establish the optical mode size of the mesa waveguide for optimum coupling to passive Silica waveguides. The expanded mode can be designed for optimum coupling directly to single mode waveguides in the second (non-semiconductor) material single-mode or to optical fibre, including 1.3 µm and 1.5 µm telecommunication fibre.
The layer structure shown m Figure 3 would be used to make a first device lOf with Quantum Wells resonant with radiation at a wavelength of around 860nm. The structure
shown in Figure 5 would be used to make a first device lOg with Quantum Wells resonant with radiation at a wavelength around 1.5 µm.
It will be appreciated that the embodiments of the invention hereinbefore described are given by way of example only, and are not meant to limit the scope thereof in any way.
It will be particularly understood that the device of the present invention is easier and simpler to manufacture than other devices, and therefore provides the potential of obtaining high quality devices at reduced cost.
It will also be appreciated that in the disclosed embodiments the mode matching means comprised a "tapered" waveguide providing a linear,_or non-linear change in width, in modified implementations the change in width may be "periodically" or "a-periodically" segmented.
It will further be understood that in this invention. Quantum Well Intermixing (QWI) is used to reduce absorption by the Quantum Well layers within the taper region. and so reduce optical losses m the taper region and improve device efficiency.
Finally, it will be appreciated that in a modification the first device may be inverted with respect to the second device, ie the ridge waveguide of the first device may be in contact with, or adjacent, a surface of the second device.







WE CLAIM:
1. An integrated optical device (5a,e) providing first (l0a-e) and second (15a,e) devices optically coupled one to the other and formed in first and second different material systems and on different substrates, one or both of the first and second devices having a Quantum Well Intermixed (QWI) region (20a-e) at or adjacent a coupling region (21a,e) between the first and second devices and said coupling region provides means (30b-f) for mode matching between the first and second devices.
2. An integrated optical device (5a,e) as claimed in claim 1, wherein the first material system is a III-V semiconductor material.
3. An integrated optical device (5a,e) as claimed in claim 2, wherein the III-V semiconductor material is selected from: Gallium Arsenide (GaAs), Aluminium Gallium Arsenide (AlGaAs) , Indium Phosphide (InP), Gallium Arsenide Phosphide (GaAsP), Aluminium Gallium Arsenide Phosphide (AlGaAsP), and Indium Gallium Arsenide Phosphide (InGaAsP).
4. An integrated optical device (5a,e) as claimed in any preceding claim, wherein the second material system is other than a III-V semiconductor material.
5. An integrated optical device (5a,e) as claimed in any preceding claim, wherein the second material system is selected from: Silica (SiO2) , Silicon (Si), Lithium Niobate (NiNbo3), a polymer, or glass, any of which are optionally doped with optically active material.
6 An integrated optical device (5a,e) as claimed in any preceding claim,
wherein the first device (l0a-e) is an optically active device.
7. An integrated optical device (5a,e) as claimed in claim 6, wherein the
optically active device is selected from one of: a laser diode, a light emitting diode (LED), an optical modulator, an optical amplifier, an optical switch or
an optical detector.
8. An integrated optical device (5a, e) as claimed in any preceding claim, wherein the second device is an optically passive device component.
9. An integrated optical device (5a, e) as claimed in claim 8, wherein the optically passive device component is a passive waveguide.
10. An integrated optical device as claimed in any preceding claim, wherein the first device provides the Quantum Well Intermixed (QWI) region.
11. An integrated optical device as claimed in claim 10 when dependent upon claim 10, wherein the means (30f) for mode matching is a waveguide provided in the first device which waveguide is a tapered waveguide providing a linear change in width, a non-linear change in width, and/or a periodic or a-periodic segmentation.
12. An integrated optical device as claimed in any preceding claim, wherein the coupling region provides anti-reflection means (25a) at or near an interface between the first and second devices.
13. An integrated optical device (5e) as claimed in claim 12, wherein the anti-reflection means comprises an anti-reflection coating (25e) on a facet of the first device (lOe) provided at the interface between the first and second devices.
14. An integrated optical device (5e) as claimed in either of claims 12 or 13, wherein the anti-reflection means (25e) comprises facets of the first and second devices provided at the interface between the first and second devices, the facets being formed at an acute angle to an intended direction of optical transmission.
15. An integrated optical device as claimed in any preceding claim, wherein a first waveguide section in the first device and optionally also a second waveguide section in the second device is /are bent.
16. An integrated optical device as claimed in any preceding claim, wherein the integrated optical device operates in a wavelength region of 600 to 1300 nm or of 1200 to 1700 nm.
17. An apparatus whenever incorporated with an optical device as claimed in any of claims 1 to 16.

Documents:

in-pct-2002-00777-del-abstract.pdf

in-pct-2002-00777-del-claims.pdf

in-pct-2002-00777-del-correspondence-others.pdf

in-pct-2002-00777-del-correspondence-po.pdf

in-pct-2002-00777-del-description (complete).pdf

in-pct-2002-00777-del-form-1.pdf

in-pct-2002-00777-del-form-19.pdf

in-pct-2002-00777-del-form-2.pdf

in-pct-2002-00777-del-form-3.pdf

in-pct-2002-00777-del-form-4.pdf

in-pct-2002-00777-del-form-5.pdf

in-pct-2002-00777-del-gpa.pdf

in-pct-2002-00777-del-pct-101.pdf

in-pct-2002-00777-del-pct-210.pdf

in-pct-2002-00777-del-pct-304.pdf

in-pct-2002-00777-del-pct-308.pdf

in-pct-2002-00777-del-pct-408.pdf

in-pct-2002-00777-del-pct-409.pdf

in-pct-2002-00777-del-pct-416.pdf


Patent Number 237409
Indian Patent Application Number IN/PCT/2002/00777/DEL
PG Journal Number 52/2009
Publication Date 25-Dec-2009
Grant Date 18-Dec-2009
Date of Filing 08-Aug-2002
Name of Patentee THE UNIVERSITY COURT OF THE UNIVERSITY OF GLASGOW
Applicant Address GILBERT SCOTT BUILDING,UNIVERSITY AVENUE,GLASGOW G12 8QQ,ENGLAND
Inventors:
# Inventor's Name Inventor's Address
1 JOHN HAIG MARSH DEPARTMENTOF ELECTRONICS AND ELECTRICAL ENGINEERING, UNIVERSITY OF GLASGOW,GLASGOW G12 8QQ,ENGLAND
2 SIMON ERIC HICKS DEPARTMENTOF ELECTRONICS AND ELECTRICAL ENGINEERING, UNIVERSITY OF GLASGOW,GLASGOW G12 8QQ,ENGLAND
3 JAMES STEWART AITCHISON DEPARTMENTOF ELECTRONICS AND ELECTRICAL ENGINEERING, UNIVERSITY OF GLASGOW,GLASGOW G12 8QQ,ENGLAND
4 BO CANG QUI DEPARTMENTOF ELECTRONICS AND ELECTRICAL ENGINEERING, UNIVERSITY OF GLASGOW,GLASGOW G12 8QQ,ENGLAND
5 STEWART DUNCAN MCDOUGALL DEPARTMENTOF ELECTRONICS AND ELECTRICAL ENGINEERING, UNIVERSITY OF GLASGOW,GLASGOW G12 8QQ,ENGLAND
PCT International Classification Number G02B 6/12
PCT International Application Number PCT/GB01/00409
PCT International Filing date 2001-01-31
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 0002775.5 2000-02-07 U.K.