GB2186144A - Optical demultiplexer - Google Patents
Optical demultiplexer Download PDFInfo
- Publication number
- GB2186144A GB2186144A GB08700322A GB8700322A GB2186144A GB 2186144 A GB2186144 A GB 2186144A GB 08700322 A GB08700322 A GB 08700322A GB 8700322 A GB8700322 A GB 8700322A GB 2186144 A GB2186144 A GB 2186144A
- Authority
- GB
- United Kingdom
- Prior art keywords
- detector
- light
- detectors
- reflected
- components
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
- 230000003287 optical effect Effects 0.000 title description 4
- 230000004888 barrier function Effects 0.000 claims abstract description 15
- 238000010521 absorption reaction Methods 0.000 claims description 12
- 238000002198 surface plasmon resonance spectroscopy Methods 0.000 claims description 12
- 229910052751 metal Inorganic materials 0.000 claims description 5
- 239000002184 metal Substances 0.000 claims description 5
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims description 3
- 229910052710 silicon Inorganic materials 0.000 claims description 3
- 239000010703 silicon Substances 0.000 claims description 3
- 239000000758 substrate Substances 0.000 claims 2
- 230000005540 biological transmission Effects 0.000 description 2
- 239000000835 fiber Substances 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 239000013307 optical fiber Substances 0.000 description 1
- 230000000063 preceeding effect Effects 0.000 description 1
- 229910052709 silver Inorganic materials 0.000 description 1
- 239000004332 silver Substances 0.000 description 1
Classifications
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/42—Coupling light guides with opto-electronic elements
- G02B6/4201—Packages, e.g. shape, construction, internal or external details
- G02B6/4204—Packages, e.g. shape, construction, internal or external details the coupling comprising intermediate optical elements, e.g. lenses, holograms
- G02B6/4215—Packages, e.g. shape, construction, internal or external details the coupling comprising intermediate optical elements, e.g. lenses, holograms the intermediate optical elements being wavelength selective optical elements, e.g. variable wavelength optical modules or wavelength lockers
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/26—Optical coupling means
- G02B6/28—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals
- G02B6/293—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means
- G02B6/29379—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means characterised by the function or use of the complete device
- G02B6/2938—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means characterised by the function or use of the complete device for multiplexing or demultiplexing, i.e. combining or separating wavelengths, e.g. 1xN, NxM
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L31/02—Details
- H01L31/0236—Special surface textures
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L31/02—Details
- H01L31/0236—Special surface textures
- H01L31/02363—Special surface textures of the semiconductor body itself, e.g. textured active layers
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L31/08—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof in which radiation controls flow of current through the device, e.g. photoresistors
- H01L31/10—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof in which radiation controls flow of current through the device, e.g. photoresistors characterised by potential barriers, e.g. phototransistors
- H01L31/101—Devices sensitive to infrared, visible or ultraviolet radiation
- H01L31/102—Devices sensitive to infrared, visible or ultraviolet radiation characterised by only one potential barrier
- H01L31/108—Devices sensitive to infrared, visible or ultraviolet radiation characterised by only one potential barrier the potential barrier being of the Schottky type
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/26—Optical coupling means
- G02B6/28—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals
- G02B6/293—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means
- G02B6/29304—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means operating by diffraction, e.g. grating
- G02B6/29305—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means operating by diffraction, e.g. grating as bulk element, i.e. free space arrangement external to a light guide
- G02B6/2931—Diffractive element operating in reflection
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Condensed Matter Physics & Semiconductors (AREA)
- Electromagnetism (AREA)
- Engineering & Computer Science (AREA)
- Computer Hardware Design (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Power Engineering (AREA)
- Optics & Photonics (AREA)
- Investigating Or Analysing Materials By Optical Means (AREA)
Abstract
A detector for demultiplexing light signals containing components of differing wavelengths (L1, L2), comprises a plurality of Schottky barrier detectors (26, 28) having parallel-grooved surfaces successively receiving the light at angles of incidence (A1, A2) such that components L1 are absorbed by plasmon resonance at Shottky barrier detector 26 and components L2 are similarly absorbed at Schottky barrier detector 28. <IMAGE>
Description
SPECIFICATION
Optical demultiplexer
Field of invention
This invention concerns optical demultiplexers by which light of one wavelength can be separated from light of another wavelength.
Background to the invention
In optical fibre communication systems, higher data transmission rates can be achieved by transmitting light signals at two differing wavelengths along the same optical path. Two preferred wavelengths for fibre optic transmission paths are 1.3 um and 1.55 um.
It is an object of the invention to provide a device by which light of one wavelength can be separated from light of the other wavelength.
It is another object of the invention to provide a device which can be adapted to separate any number of light signals provided they are all of differing wavelengths.
Summary of the invention
According to the present invention a detector which is capable of demultiplexing n light signals each having a different wavelength L1, L2 .... Ln comprises a first Schottky barrier detector the light receptive surface of which is profiled with a plurality of parallel grooves or ridges so that surface plasmon resonance will occur if light is incident then and (n-1) further Schottky barrier detectors each having a light receptive surface which is profiled in a similar manner to the first; projection means for projecting light containing all n signals onto the light receptive surface of a first of the detectors at an angle of incidence Al, such that surface plasmon resonance, and therefore absorption, will occur in respect of any component having a wavelength L1, all other components being reflected by the surface, and wherein a second one of the detectors is arranged to receive any light reflected by the first detector surface at an angle of incidence A2 such that surface plasmon resonance (and therfore absorption) will ocur at the second detector in respect of any component having a wavelength L2, all other components being reflected by the surface, and each of the (n-2) remaining detectors is arranged to receive light in its turn from a preceeding detector in a manner similar to that in which the said second detector, receives light from the first detector at angles of incidence A3, A4 .. An, such that resonance (and therefore absorption) will occur at each said detector in respect of a different one of the components L3, L4 .... Ln, and any remaining components will be reflected.
The condition for establishing surface plasmon resonance is related to the groove pitch Ag, the light wavelength A, and the angle of incidence U by the equation (to first order):
where Em is the (complex) dielectric constant of the metal. For typical metals, Em is nearly real, negative, and has modules much larger than unity (eg. silver, Em - -40 in the visible range). Thus the quantity (Em/Em+1)z is very close to unity. Generally, therefore:1 n 1 - sinO+~ - A, Ag A, which corresponds to the equation identifying diffraction of light by a grating, when the nth diffracted order emerges at an angle of 900 to the normal (ie. skims the surface of the metal).
In the simple case in which it is derived to separate two components L1 and L2 both present in an input signal, two detectors are provided, one receptive of the light signal at an angle of incidence Al such that any L1 component sets up surface plasmon resonance in the first detector surface and is therefore absorbed and detected, whilst all other wavelengths (including
L2) are reflected, and a second detector positioned relative to the first so as to receive any light reflected from the first detector at an angle of incidence A2, such that any component of wavelength L2 is absorbed (and therefore detected) by the second detector.
The invention will be described by way of example with reference to the accompanying drawings in which:
Figure 1 is an enlarged cross section through a Schottky barrier detector having a profiled surface as required by the invention,
Figure 2 illustrates graphically the variation of reflected energy with wavelength, for a given angle of incidence, and
Figure 3 illustrates diagramatically how two detectors can be arranged to provide for demultiplexing two signals L1 and L2.
In Fig. 1 a Schottky barrier detector is shown in part as being formed from n-type silicon (layer 10), and a thin metal layer 12, forming a receiving and reflecting surface 14. The silicon is profiled so as to define a plurality of parallel grooves 16, 18 etc. separated by ridges 20, 22 etc..
A light beam 24 is shown incident on the surface 24 at an angle A. If the wavelength of the light in the beam 24 is varied in the range of wavelengths LA to LB then for a given spacing and depth of the grooves 16, 18 etc, a response curve of reflected energy against wavelength will be obtained as is shown in Fig. 2. Here reflected power R is plotted against wavelength and it will be seen that at one particular wavelength. LF, the reflected energy is substantially zero. It is at this wavelength that surface plasmon resonance occurs, resulting in virtually 100% absorption of the light of that wavelength.
A similar response curve is obtained if, instead of varying wavelength, light of constant wavelength is projected onto a profiled surface at differing angles of incidence.
In the present invention, this fact is utilised to advantage in that the angle of incidence Al is selected so that resonance (and therefore absorption) occurs at wavelength L1 at detector 26 leaving predominantly L2 components to pass to detector 28. This is angled relative to 26 so that the angle of incidence A2 is such that resonance and absorption occur at wavelength L2 at the second detector.
The electrical output from detector 36 will thus be proportional to the L1 wavelength component and that from 28 will be proportional to the L2 wavelength component, in the input light beam 30.
Claims (7)
1. According to the present invention a detector which is capable of demultiplexing n light signals each having a different wavelength L1, L2 .... Ln comprises a first Schottky barrier detector the light receptive surface of which is profiled with a plurality of parallel grooves or ridges so that surface plasmon resonance will occur if light is incident therein and (n-1) further
Schottky barrier detectors each having a light receptive surface which is also profiled with parallel grooves or ridges; projection means for projecting light containing all n signals onto the light receptive surface of a first of the detectors at such an angle of incidence that surface plasmon resonance, and therefore absorption, will occur in respect of any component having a wavelength L1, all other components being reflected by the surface, and wherein a second one of the detectors is arranged to receive any light reflected by the first detector surface at such an angle of incidence that surface plasmon resonance (and therefore absorption) will occur at the second detector in respect of any component haveing a wavelength L2, all other components being reflected by the surface, and each of the (n-2) remaining detectors is arranged to receive light in its turn from a preceding detector, in a manner similar to that in which the said second detector receives light from the first detector, each at such an angle or incidence that resonance (and therefore absorption) will occur at each said detector in respect of a different one of the components L3, L4 .... Ln, and any remaining components will be reflected.
2. A detector capable of demultiplexing n light signals each having a different wavelength L1,
L2 ... Ln, comprising a first Schottky barrier detector the light receptive surface of which is profiled with a plurality of parallel grooves or ridges so that surface plasmon resonance will occur if light is incident therein and (n- 1) further Schottky barrier detectors each having a light receptive surface which is profiled in a similar manner to the first; projection means for projecting light containing all n signals onto the light receptive surface of a first of the detectors at an angle of incidence Al, such that surface plasmon resonance, and therefore absorption, will occur in respect of any component having a wavelength L1, all other components being reflected by the surface, and wherein a second one of the detectors is arranged to receive any light reflected by the first detector surface at an angle of incidence A2 such that surface plasmon resonance (and therefore absorption) will occur at the second detector in respect of any component having a wavelength L2, all other components being reflected by the surface, and each of the (n-2) remaining detectors is arranged to receive light in its turn from a preceding detector, in a manner similar to that in which the said second detector receives light from the first detector, at angles of incidence A3, A4 .. An, such that resonance (and therefore absorption) will occur at each said detector in respect of a different one of the components L3, L4 .. . Ln, and any remaining components will be reflected.
3. A detector according to claim 1 or 2, comprising two Schottky barrier detectors for separating light signals of two differing wavelengths.
4. A detector according to any one of claim 1 to 3, wherein each Schottky barrier detector comprises an n-type silicon substrate having a profiled surface and a thin metal layer of uniform thickness deposited on the profiled surface of the substrate.
5. A detector according to any of claims 1 to 4, wherein each Schottky barrier detector is profiled with a smoothly undulating surface forming a series of alternating parallel grooves and ridges.
6. A detector according to any of claims 1 to 5, including means for measuring the electrical output of each of the Schottky barrier detectors.
7. A detector capable of demultiplexing n light signals respectively having differing wavelengths L1, L2 . . Ln substantially as hereinbefore described with reference to the accompanying drawings.
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| PCT/GB1987/000061 WO1987004862A1 (en) | 1986-01-30 | 1987-01-29 | Optical demultiplexer |
| EP87901072A EP0256075A1 (en) | 1986-01-30 | 1987-01-29 | Optical demultiplexer |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB868602309A GB8602309D0 (en) | 1986-01-30 | 1986-01-30 | Optical memultiplexer |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB8700322D0 GB8700322D0 (en) | 1987-02-11 |
| GB2186144A true GB2186144A (en) | 1987-08-05 |
Family
ID=10592240
Family Applications (2)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB868602309A Pending GB8602309D0 (en) | 1986-01-30 | 1986-01-30 | Optical memultiplexer |
| GB08700322A Withdrawn GB2186144A (en) | 1986-01-30 | 1987-01-08 | Optical demultiplexer |
Family Applications Before (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB868602309A Pending GB8602309D0 (en) | 1986-01-30 | 1986-01-30 | Optical memultiplexer |
Country Status (2)
| Country | Link |
|---|---|
| JP (1) | JPS63502545A (en) |
| GB (2) | GB8602309D0 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2004079829A1 (en) * | 2003-03-04 | 2004-09-16 | Spectalis Corp. | Schottky barrier photodetectors |
-
1986
- 1986-01-30 GB GB868602309A patent/GB8602309D0/en active Pending
-
1987
- 1987-01-08 GB GB08700322A patent/GB2186144A/en not_active Withdrawn
- 1987-01-29 JP JP62500986A patent/JPS63502545A/en active Pending
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2004079829A1 (en) * | 2003-03-04 | 2004-09-16 | Spectalis Corp. | Schottky barrier photodetectors |
| US7026701B2 (en) | 2003-03-04 | 2006-04-11 | Spectalis Corp. | Schottky barrier photodetectors |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS63502545A (en) | 1988-09-22 |
| GB8700322D0 (en) | 1987-02-11 |
| GB8602309D0 (en) | 1986-03-05 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |