CN1178011A - Method of writing photosensitive grating using Lcoyd's mirror - Google Patents
Method of writing photosensitive grating using Lcoyd's mirror Download PDFInfo
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- CN1178011A CN1178011A CN 97190021 CN97190021A CN1178011A CN 1178011 A CN1178011 A CN 1178011A CN 97190021 CN97190021 CN 97190021 CN 97190021 A CN97190021 A CN 97190021A CN 1178011 A CN1178011 A CN 1178011A
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- waveguide
- grating
- catoptron
- light beam
- index
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Abstract
Apparatus for forming a refractive index grating in a waveguide in accordance with the invention includes a waveguide formed from a material that changes its index of refraction when exposed to a beam of optical radiation, a source of coherent optical radiation for forming a beam of radiation, a mirror arranged to intercept a first part of a beam and to reflect the first part of the beam through an angle, and a phase delay plate arranged to intercept a second part of the beam for delaying the second part of the beam propagating through the plate, in which the mirror and the phase delay plate are arranged so that the first part of the beam and the second delayed part of the beam form an interference pattern on the waveguide for changing the index of refraction of the waveguide, in a pattern corresponding to the interference pattern for forming an index grating in the waveguide.
Description
Background of invention
Present invention relates in general to a kind of method and apparatus that in waveguide, forms cloth loudspeaker lattice refractive-index grating, relate in particular to a kind of method that forms this class grating with Lloyd mirror and phase retardation plate, here the effect of phase retardation plate is with the position deviation catoptron of grating and the interface between the waveguide, to produce long and preferably symmetrical grating.
For comprising many application such as communication, optical waveguide (comprising fibre-optic waveguide and planar waveguide) has become more and more important.Inside comprises light waveguide raster especially comprises refractive-index grating in waveguide cores waveguide has realized providing specific function in waveguide with preferred mode many devices.A kind of method of making light waveguide raster is to form a beam pattern with the two beam interferometer light beams that the single-frequency laser instrument is derived, if the intensity of light beam is enough strong, after after a while, a refractive-index grating can be write in the waveguide cores so.As everyone knows, can form Bragg grating in this way.
Formed Bragg grating can be lasting, also can be of short duration, so-called being meant of continuing forms permanent grating in fact in fibre core, and grating exists after removing the radiation that forms grating, and so-called of short duration being meant when having only the radiation incident fibre core that forms grating grating just exist.For example, people's such as Faco patent is described this for the 5th, 218, No. 651.
In order to form high-quality grating, need reduce the secondary lobe that is arranged in the light filter loss spectra that produces in the optical fiber with the long light source of coherent length.Can buy the long light source of coherence of dye laser and so on, but it costing an arm and a leg, is not durable especially, is difficult to tuning and keeps tuning, and generally can not satisfy in production environment and use.Excimer laser is suitable for producing according to characteristics such as its price, durability and stability, and when with the phase mask coupling, be suitable for writing grating, but the coherent length of this laser instrument can not form Bragg grating than the weak point of dye laser for this reason in waveguide.
An object of the present invention is to provide a kind of method and apparatus that in waveguide, forms refractive-index grating, it can overcome the shortcoming of known method and equipment, and the present invention especially provides the method and apparatus of a kind of permission at the light source that the use coherent length is lacked in improved Laue moral mirror approach that is specially adapted to production environment.
In brief, the method that forms refractive-index grating according to preferred embodiment of the present invention in waveguide may further comprise the steps: a lateral edges that waveguide is positioned at catoptron; The first of optical radiation coherent light beam is incided on the catoptron with first angle, and the second portion of optical radiation coherent light beam is incided on the phase retardation plate of light; First and second parts are merged into a branch of interfering beam, and interfering beam is incided in the waveguide, in waveguide, to form a grating.
According to another embodiment of the present invention, the phase retardation plate of light comprises a quartz plate, and it makes the retardation of the second portion of light beam be enough to make interference figure to move apart the edge of catoptron.
According to another aspect of the present invention, it is enough far away to make grating pattern leave the catoptron edge, to form the grating of symmetry in waveguide.
The equipment that forms refractive-index grating according to the present invention in waveguide comprises: a waveguide, and when waveguide is exposed to light radiation laser beam following time, its building material can change its refractive index; The light source that one optical radiation is relevant is used to form radiation laser beam; One catoptron is used to intercept the first of light beam, and the first by a certain angle folded light beam; One phase retardation plate is used to intercept the second portion of light beam, and the second portion of the light beam of propagating by this plate is postponed.Wherein the layout of catoptron and phase retardation plate makes the first of light beam and delayed light beam second portion form an interference figure in waveguide, to change waveguide index in the pattern in order to the corresponding interference figure that forms refractive-index grating.
According to one side more of the present invention, the layout of catoptron and phase retardation plate can form a symmetrical pattern in waveguide, and pattern center departs from the boundary line of waveguide and catoptron.
Summary of drawings
Novel aspect of the present invention will be described by the concrete restriction of appended claims, and will understand invention itself and other purpose and advantage fully with reference to following detailed description about preferred embodiment of the present invention in conjunction with the accompanying drawings, and accompanying drawing has:
Fig. 1 is the equipment synoptic diagram that forms refractive-index grating according to the present invention in waveguide.
The detailed description of preferred embodiment
Referring now to Fig. 1, in optical fiber or planar waveguide 10, form a refractive-index grating.A lateral edges of catoptron 12 is fixed in waveguide, and wave guide direction is generally perpendicular to first reflecting surface 14 of catoptron 12.The most handy light beam that can produce ultraviolet variations in refractive index produces radiation 20, preferably produce radiation by excimer laser, thereby make first's incidence reflection mirror of light beam, and second portion is led directly into ejected wave.Can use wavelength to be in light beam between about 193-514 nanometer.Preferably arrange the phase retardation plate 22 of a quartz, the second portion that only makes incident beam is by this plate.The selection of phase delay plate thickness should be able to vertically make the light beam second portion and the interference figure axial centre of the waveguide that reflects the formation of back light beam first and the boundary line of mirror reflection face of direct incident along waveguide.Found to be about 13 when spending when the residing half-angle of catoptron, the thickness of being made by quartz is about about 1 millimeter of the boundary line that 1 millimeter phase retardation plate can make Bragg grating misalignment catoptron and waveguide.
By the half-angle of the relative incident beam of accommodation reflex mirror, just can regulate light wavelength behind optical grating reflection (cloth loudspeaker lattice wave is long).Cloth loudspeaker lattice wavelength X
BraggCan be expressed as:
λ
Bragg＝N
effλ
write/sin0
Wherein, N
EffBe the effective refractive index of waveguide, and λ
WriteIt is the wavelength of ultraviolet beam.According to the present invention, half-angle preferably is between 10 to 15 degree.
Waveguide is planar waveguide or fibre-optic waveguide preferably.Waveguide cores is preferably to the incident beam sensitivity, thereby can change the refractive index of fibre core.For example, the quartzy cladded-fiber of germanium silicate (germanosilicate silicaclad fiber) in 240 nanometers to the UV radiation sensitivity, thereby produce enough variations in refractive index, form with 5: 12.5 molar percentage doped with Ge O
2Bragg grating.For example, can use 6.6% doping that has on the market.According to the present invention, the concentration of germanium can from less than 1% until near 100%.Form the necessary exposure length of effective grating and depend on radiation intensity.When fibre core exposes about 20 minutes the time, the average light power of about 4.5 milliwatts can produce effective Bragg grating.Luminous power is enhanced to about 18.5 milliwatts can in about 5 minutes, produces stronger grating.
As long as optical fiber is not overheated, the Bragg grating that forms with this method is permanent basically.The grating that forms according to the inventive method can stand many hours performances deterioration not basically under 500 ℃ of high temperature.
Can in waveguide, form interim or of short duration layer, wherein waveguide cores makes the material of light amplification by a kind of through optical pumping, and the pumping wave that is produced can produce a variable interference field at least in fibre core, interference field is included in the striations that produces in the core light amplified material, and temporary layer extends on a part of fibre core of waveguide at least.As long as have only or have pumping wave, just interference field can appear.
With Laue moral catoptron but in the method without the present invention's phase retardation plate, require to have long temporal coherence, but can reduce this requirement according to the present invention forms Bragg grating in waveguide method.The layout of Laue moral catoptron comes down to utilize ultraviolet wavefront, and ultraviolet ray is turned back, to produce interference figure.Because light beam itself is turned back, thus in order to produce required interference figure, must be on the length of the lap of light beam first and second parts space relevant.For the lower light source of coherence excimer laser (because of discussed former thereby need to use) for example, expand bundle by light beam to excitation laser, can improve spatial coherence.But if the temporal coherence of light source is shorter, for example the coherence of excimer laser is the hundreds of microsecond, and this has still limited the length of grating so.
By inserting the first half of light beam, can make the zero propagation position between the first half light beam and the latter half light beam move on the optical fiber a higher position from the boundary line of waveguide and catoptron such as quartz plate equiphase retardation plate.Quartz plate is thick more, and the zero propagation position moves up highly more along waveguide.The method of adding phase retardation plate according to the present invention has increased more than 2 times grating length.
Another advantage that forms the method and apparatus of grating according to the present invention is that formed grating is symmetrical, promptly vertically the central peak of grating is departed from the boundary line of waveguide and catoptron along waveguide, moves to along on a certain position of optical fiber vertical shift.If vertical shift is the grating length that produces half at least, grating is symmetrical so.Because symmetrical grating can reduce the secondary lobe in the grating transport function, so need to use symmetrical grating.
According to one embodiment of the present of invention, can be placed down in the SMF-28 optical fiber that surpasses 7 days in the 100 atmospheric pressure hydrogen to room temperature according to the present invention and expose.Catoptron becomes 13.5 ° of fixed angle with the incident uv bundle, and the wavelength of light beam is 240 nanometers.The thickness of phase retardation plate is 1 millimeter, and this plate is fixed on not by in the light beam of the Laue moral mirror reflects part.
After about 4 minutes to exposed optical fiber, to form a grating, about 1 millimeter of the centre distance Laue moral catoptron of grating and the boundary line of optical fiber, and the candy strip of grating is symmetrical substantially, these grating fringes are producing big decay in the transmission near 1,478 nanometer.
Claims (10)
1. a method that forms refractive-index grating in waveguide is characterized in that, may further comprise the steps:
Described waveguide is positioned at a lateral edges of catoptron;
The first of a branch of relevant optical radiation is incided on the described catoptron with first angle, and the second portion of the optical radiation of this Shu Xianggan is incided on the phase retardation plate of light;
Described first and second parts are merged into a branch of interfering beam, and described interfering beam is incided in the described waveguide, in described waveguide, to form a grating.
2. the method for claim 1 is characterized in that, the described step that forms grating in waveguide comprises permanent grating of formation.
3. the method for claim 1 is characterized in that, the described step that forms grating in waveguide comprises interim grating of formation.
4. the method for claim 1 is characterized in that, the phase retardation plate of described light comprises a quartz plate.
5. method as claimed in claim 4 is characterized in that, the retardation that described quartz plate produces the second portion of described light beam is enough to make interference figure to depart from the edge of catoptron.
6. method as claimed in claim 4 is characterized in that, makes the displacement of interference figure enough big, to form the grating of a symmetry in waveguide.
7. the method for claim 1 is characterized in that, described waveguide comprises a fibre-optic waveguide.
8. the method for claim 1 is characterized in that, described waveguide comprises a planar waveguide.
9. be used for forming the equipment of refractive-index grating, it is characterized in that, comprising in waveguide:
One waveguide, when exposing under light radiation laser beam, its building material can change its refractive index;
The light source of one coherent optical radiation is used to form radiation laser beam;
One catoptron is used to intercept the first of light beam, and the first by φ angle folded light beam;
One phase retardation plate is used to intercept the second portion of light beam, and the second portion of the light beam of propagating by this plate is postponed;
The layout of catoptron and phase retardation plate makes and forms an interference figure through beam reflected first and delayed light beam second portion in waveguide, to change waveguide index in the pattern that forms refractive-index grating.
10. equipment as claimed in claim 10 is characterized in that, the layout of catoptron and phase retardation plate can form a symmetrical pattern in waveguide, and pattern center departs from the boundary line of waveguide and catoptron.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 97190021 CN1178011A (en) | 1996-01-29 | 1997-01-17 | Method of writing photosensitive grating using Lcoyd's mirror |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US08/593,637 | 1996-01-29 | ||
| CN 97190021 CN1178011A (en) | 1996-01-29 | 1997-01-17 | Method of writing photosensitive grating using Lcoyd's mirror |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN1178011A true CN1178011A (en) | 1998-04-01 |
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ID=5178589
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN 97190021 Pending CN1178011A (en) | 1996-01-29 | 1997-01-17 | Method of writing photosensitive grating using Lcoyd's mirror |
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|---|---|
| CN (1) | CN1178011A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101819323A (en) * | 2010-05-17 | 2010-09-01 | 中国科学院长春光学精密机械与物理研究所 | Method for adjusting verticality between Lloyd mirror and grating substrate in Lloyd mirror device |
-
1997
- 1997-01-17 CN CN 97190021 patent/CN1178011A/en active Pending
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101819323A (en) * | 2010-05-17 | 2010-09-01 | 中国科学院长春光学精密机械与物理研究所 | Method for adjusting verticality between Lloyd mirror and grating substrate in Lloyd mirror device |
| CN101819323B (en) * | 2010-05-17 | 2011-07-20 | 中国科学院长春光学精密机械与物理研究所 | Method for adjusting verticality between Lloyd mirror and grating substrate in Lloyd mirror device |
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