CN109164526A - A kind of unpolarized type narrow-band optical bandpass filter - Google Patents
A kind of unpolarized type narrow-band optical bandpass filter Download PDFInfo
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- CN109164526A CN109164526A CN201811085460.3A CN201811085460A CN109164526A CN 109164526 A CN109164526 A CN 109164526A CN 201811085460 A CN201811085460 A CN 201811085460A CN 109164526 A CN109164526 A CN 109164526A
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Abstract
The invention belongs to Guided Wave Technique field, specially a kind of unpolarized type narrow-band optical bandpass filter.Optical filter of the invention, the central wavelength of the passband of its H mode and transverse magnetic wave is overlapped, and the passband width of two kinds of waves is narrowband, it include: the composite transparencies of a cylinder or square body and planar optical waveguide, wherein by cylinder or square body along the angled incision of the longitudinal axis, according to centre of homology wavelength on a section, planar optical waveguide is prepared, planar optical waveguide is made of the film of the different numbers of plies and thickness, and ducting layer of the present invention has the periodic structure of high low-refraction；Two cutting bodies are closed along section note again, it is fixed, and seal, constitute complex；Complex both ends of the surface are coated with broadband anti-reflection film.For this bandpass filter central wavelength transmitance up to 100%, bandwidth, which can design, reaches sub-nanometer magnitude, has important application in terms of optical communication, laser technology, precision, and prepare simply, easy to use.
Description
Technical field
The invention belongs to Guided Wave Technique fields, and in particular to a kind of narrow-band optical bandpass filter of unpolarized type.
Background technique
Narrow band optical filter is essential optical device in terms of optical communication, spectral technique.It can produce narrow band light
The technology for learning filtering is existing very much, such as optical thin film, interferometric filter, and the filtering of the guide mode resonance based on wave-guide grating structure
Device etc..What the transmission that these optical filtering technologies are mainly all based on polarised light was designed, therefore be polarization independent, that is, it filters
The H mode (TE) of wave device and the bandpass center of transverse magnetic wave (TM) are not overlapped.So-called H mode (abbreviation TE wave) is light wave
The light wave for the plane that polarization direction is constituted perpendicular to the normal of slab guide and the wave vector direction of light wave, transverse magnetic wave (abbreviation TM wave)
It is the light wave that the polarization direction of light wave is parallel to the plane of the normal of slab guide and the wave vector direction composition of light wave.
So-called unpolarized type optical band pass filter, the passband of the H mode and transverse magnetic wave that refer to filter are center weights
It closes.I.e. passband is under this central wavelength, it can logical H mode can also lead to transverse magnetic wave.With the hair of optical communication technology
Exhibition, the demand to unpolarized narrow band optical filter are more and more.Therefore, it studies to the light wave of different polarization states with identical
The unpolarized type narrow band optical filter of passband just becomes a kind of theoretical and real work important topic.
There is document report to may be implemented by using the guide mode resonance filter of the wave-guide grating structure of two-dimensional grating non-
The optically filtering of polarization-type narrowband acts on, in addition, by using two layers of ducting layer, and the space spacing of two ducting layers is controlled,
The optically filtering effect of unpolarized type narrowband also may be implemented in the filter of one-dimensional wave guide optical grating construction.It is well known that being based on wave
The narrow-band optical bandpass filter of guide grating can encounter many technical difficulties in device preparation, this is mainly grating
Period is usually sub-wavelength, therefore the cost for preparing precision and preparation can be come complicated than the homogeneous texture of non-grating.
Unpolarized type narrow-band optical bandpass filter proposed by the present invention is the guide mode resonance optical filtering skill based on prism-coupled
Art, compared with the guide mode resonance technology of optical grating construction, grating is not contained in device architecture of the invention, therefore system can be saved
The complicated technology of the optical grating construction of standby sub-wavelength improves device so as to greatly simplify the preparation process and expense of device
Quality.And it is easy to use there is no need to carry out angle adjustment due to having determined that the direction of incident light is normal incidence when design.
Summary of the invention
The purpose of the present invention is to provide it is a kind of prepare it is simple, have excellent performance, unpolarized type narrowband optical easy to use
Bandpass filter.
Based on the principle of prism-coupled planar optical waveguide, the unpolarized type narrow-band optical bandpass filter that the present invention designs,
It is the narrow band optical filter based on prism-coupled guide mode resonance, the passband center wavelengths of H mode (TE) and transverse magnetic wave (TM)
It is overlapped, and the passband width of two kinds of waves is narrowband；Its passband center wavelengths transmitance is up to 100%, pass band width Da Yana
Rice (nm) magnitude, structure are as shown in Figure 1.Specifically include: a collimated incident beam, one by cylinder (such as cylinder or square body)
The composite transparencies (hereinafter referred to as complex) of two cutting bodies and the planar optical waveguide composition formed through cutting；Wherein, two
Cutting body is symmetrical two parts obtained from being cut as cylinder (such as cylinder or square body) along the longitudinal axis angled (A),
It is planar optical waveguide between the opposite section (inclined-plane) of two cutting bodies, the planar optical waveguide is by coupling layer-ducting layer-coupling
The basic structure for closing layer is constituted, wherein two coupling layers depend on the inclined-plane of two cylinders after cutting respectively, and ducting layer is sandwiched in
Between two coupling layers, and ducting layer is coincided by the period film layer of height combination of refractive indices and is constituted.Ducting layer and two cylinder structures
It is still a cylinder at a complex；The both ends of the surface of complex are formed with broadband anti-reflection film.
When preparation, cylinder first can be obtained symmetrical two cutting bodies along the longitudinal axis angled (A) incision, be cut at one
It cuts on body section (inclined-plane) according to centre of homology wavelength, prepares planar optical waveguide；Planar optical waveguide is by the different numbers of plies and thickness
Film is constituted；Two cutting bodies are closed along section note again, it is fixed, and seal, that is, constitute complex；Complex both ends of the surface are coated with width
Band anti-reflection film.Light beam is transmitted along the complex longitudinal axis when use.Angle A=90 °-θ, θ are greater than cutting body and waveguide coupling layer
C: θ c=asin (n of critical angle θ4/n3).Wherein, n4And n3The respectively refractive index of cutting body and waveguide coupling layer.Generally, θ
Value be taken as the position of peak value occur being greater than critical angle and transmitance.After the angle θ determines, the value at the angle A is also assured that.
Filter of the invention has important application in optical communication, spectral technique etc..The present invention is based on prism-coupleds
Guide mode resonance principle, it is not necessary to prepare optical grating construction, therefore have that preparation is convenient, using simplicity, the advantages of narrow bandwidth.
In the present invention, the collimated incident beam is collimated light beam.
In the present invention, broadband anti-reflection film that the antireflective coating of the both ends of the surface is coated with for the central wavelength according to design
Layer.
In the present invention, the Refractive Index of Material of the cylinder (cylinder or square body) cutting body is higher than the coupling of planar optical waveguide
Close the refractive index of layer.
In the present invention, the planar optical waveguide, two sides are the coupling layers of low-refraction, and middle layer is ducting layer, by
The period film layer of height combination of refractive indices adds a high refractive index layer to constitute again.What ducting layer can also be combined by low high refractive index
Period film layer adds a low-index film to constitute again.The refractive index of ducting layer is higher than the coupling layer refractive index of two sides.
In the present invention, the cylinder is cylindrical body or square body, and the section of two cutting bodies is inclined-plane, when cylinder is cylinder
When body, section is ellipse, and when cylinder is square body, section is rectangle.
In the present invention, described two low-refraction coupling layers and high refractive index ducting layer, both high and low refractive index is phase
It is relative.
The material of the low-index film can be air, or uniformly and to treat the transparent gas of filter section, liquid
Or solid.
The invention has the advantages that
1, great advantage of the invention can be achieved on is overlapped through the H mode of filter and the bandpass center of transverse magnetic wave,
Realize so-called unpolarized type narrow-band bandpass optical filter；
2, structure of the invention is a kind of planar optical waveguide conducting structure based on prism-coupled, relative to grating coupled
Structure, great advantage is not have to grating, therefore eliminate the complex process for preparing sub-wave length grating, only with certain plated film work
Skill installs additional with can be completed, and can equally reach 100% transmitance, and pass band width also can reach sub-nanometer magnitude；
3, yet another advantage of the present invention is that, by the cutting angle of design, it may insure incident light in a manner of normal incidence
Through the filter, without complicated angle adjusting mechanism, to have the characteristics that easy to use and easy.
Detailed description of the invention
Fig. 1 is a kind of structural schematic diagram of unpolarized type narrow-band optical bandpass filter.
Fig. 2 is the refractive index spatial distribution of planar waveguide layers normal direction (direction N) in filter construction shown in Fig. 1.
Fig. 3 enters light beam to the H mode of planar waveguide layers in prism coupling structure shown in Fig. 1 for (wavelength 632.8nm's)
(TE) intensity transmitance with incidence angle variation relation.
Fig. 4 is that the H mode (TE) of filter shown in Fig. 1 and the transmitted spectrum of transverse magnetic wave (TM) (set the both ends of the surface of complex
100%) transmitance is.Incidence angle is 60.180 ° at this time.
Fig. 5 is that (both ends of the surface for setting complex are saturating for the transmitted spectrum of filter H mode (TE) and transverse magnetic wave (TM) shown in Fig. 1
100%) crossing rate is.At this point, the 3rd thickness degree in ducting layer reduces 10nm.
Fig. 6 is that (both ends of the surface for setting complex are saturating for the transmitted spectrum of filter H mode (TE) and transverse magnetic wave (TM) shown in Fig. 1
100%) crossing rate is.At this point, the 3rd thickness degree in ducting layer increases 10nm.
Figure label: 1 is collimated incident beam, and 2 and 8 be end face antireflective coating, and 3 and 7 be cylinder or square body cutting body,
4 be low-refraction coupling layer, 5 high refractive index ducting layer, 6 low-refraction coupling layers.Wherein shown in high refractive index ducting layer 5
Ducting layer adds a high refractive index layer to constitute again by the period film layer of height combination of refractive indices.Ducting layer can also be by low high refraction
The period film layer of rate combination adds a low-index film to constitute again.The refractive index of ducting layer is higher than the coupling layer refractive index of two sides.
Specific embodiment
A kind of unpolarized type narrow-band optical bandpass filter that the present invention designs a, comprising: cylinder or square body and flat
Composite transparencies (hereinafter referred to as complex) of face optical waveguide wherein by cylinder or square body along the angled incision of the longitudinal axis,
According to centre of homology wavelength on a section, prepare planar optical waveguide, planar optical waveguide by the different numbers of plies and thickness film
Is constituted again to close two cutting bodies along section note, it is fixed, and seal, constitute complex.Complex both ends of the surface are coated with broad-band transparence-increased
Film.
Narrow band filter of the invention, specifically includes: collimated incident beam 1, end face antireflective coating 2 and 8, cylinder or square column
Body cutting body 3 and 7, planar optical waveguide, by low-refraction coupling layer 4, high refractive index ducting layer 5,6 structure of low-refraction coupling layer
At, wherein ducting layer shown in 5 adds a high refractive index layer to constitute again by the period film layer of height combination of refractive indices, ducting layer
The period film layer that can also be combined by low high refractive index adds a low-index film to constitute again.The refractive index of ducting layer is higher than two sides
Coupling layer refractive index.Its structural schematic diagram is as shown in Figure 1.
Low-refraction coupling layer 4 in the planar optical waveguide is a low-index film, for connecting 5 He of ducting layer
Cutting body 3, prepare material can be air or for uniformly and treat the transparent gas of filter section, liquid, or solid.
5 refractive index of high refractive index ducting layer in the planar optical waveguide is higher than low-refraction coupling layer 4 and 6.
Low-index film 6 in the planar optical waveguide is a low-index film, is led for connecting high refractive index
Wave layer 5 and cutting body 7.
Structure according to figure 1 selectes a laser work wavelength such as: 632.8nm, and cylindrical material is dense flint glass
Glass, refractive index 1.75, using it as couple prism body material planar waveguiding structure in grazing shot rate coupling layer 4 and 6, be taken as melting
Quartz, refractive index 1.45, thickness, which is controlled, to be made of in 600nm. high refractive index ducting layer 5 two kinds of materials, material dense flint glass
Glass, refractive index 1.75 and barium crown glass, refractive index are that two kinds of material thickness of 1.57. are taken as 345nm and 200nm composition respectively
Periodic structure, in this example, periodicity 3, then increase by one layer of high refractive index layer behind, with a thickness of 345nm.Total
Refractive index it is as shown in Figure 2 along the distribution of the normal direction of slab guide；In the coordinate system established, along the normal of slab guide
The direction N is taken as X, and compound body axis direction is taken as Z.
Using stringent coupled-mode theory, after a branch of collimated light beam enters the filter, in each section of filter
The field strength expression formula of light field can be stated with following equation: by taking H mode (TE wave) as an example, in the coordinate system of such as Fig. 1:
Index number represents structural region where light field in above formula, and the coefficient λ that A, B represent related intrinsic wave represents wave and exists
The characteristic value of relevant range,niIndicate the refractive index of corresponding region, diIndicate the thickness of corresponding region, i
=3,4,5,6,7, β are the propagation vector of the light along Z-direction.
Using TE wave electric field intensity boundary the condition of continuity, and assume incident field complex cutting body 3 with
The light field amplitude of 4 interface of low-refraction coupling layer is 1, can solve distribution of light intensity and light of the light in cutting body 7 and cut
The ratio of distribution of light intensity in body 3, i.e. transmitance:The transmissivity formula of TM wave has similarity therewith, and difference exists
In nonexponential place, characteristic value λiIt will be divided by square of the refractive index in corresponding regionCalculated result as shown in Figure 3 can
See from 55 ° to 90 °, transmissivity under multiple angles can when reach 100% transmitance, and angular range
Very little.
The filter is transmitted with the collimated light beam of certain bandwidth, the spectral transmittance of TE and TM wave as shown in Figure 4 is at this time
Incidence angle is 60.180 °.The spectral band-width center of TE and TM wave is overlapped, and bandwidth is very narrow, and full width at half maximum degree is respectively
0.51nm and 0.74nm.
Fig. 5 and Fig. 6 is respectively that guided wave leads thickness in the 3rd layer in 5 and reduces and increase the transmission of 10nm later TE and TM
Spectrum, the two central wavelength are no longer overlapped.It can be seen that can effectively control two kinds of polarised lights by the thickness for controlling a certain film layer
The center of passband realizes that center is overlapped, to realize unpolarized type narrowband optical bandpass filtering effect.
In addition, by the optimization of structural parameters, we also realized at 632.8nm wavelength bandwidth be 16.5pm and
The unpolarized type narrowband optical bandpass filtering of 6.8pm acts on, meanwhile, also in 1.55 mu m wavebands of optical communication, devise TE and TM
The bandwidth of wave is respectively the unpolarized type narrow-band optical bandpass filter structure of 0.58 and 0.82nm.
Claims (8)
1. a kind of unpolarized type narrow-band optical bandpass filter, the i.e. passband center wavelengths of its H mode and transverse magnetic wave are overlapped,
And the passband width of two kinds of waves is narrowband；It is characterised by comprising: a branch of collimated incident beam, one by cylinder through cutting
The composite transparencies of two cutting bodies and the planar optical waveguide composition formed, hereinafter referred to as complex；Wherein:
Two cutting bodies are symmetrical two parts obtained from being cut as cylinder along the angled A of the longitudinal axis, are cut at this two
It cuts for planar optical waveguide between the opposite section of body, the planar optical waveguide is by coupling layer-ducting layer-coupling layer basic structure structure
At；Wherein, two coupling layers depend on the inclined-plane of two cylinders after cutting respectively, and ducting layer is sandwiched between two coupling layers,
And ducting layer is coincided again by the period film layer of height combination of refractive indices plus a high refractive index layer is constituted；Ducting layer and two cylinders
A complex is constituted, is still a cylinder；The both ends of the surface of complex are formed with broadband anti-reflection film；Here, angle A=90 °-q, q
Greater than critical angle qc:qc=asin (n of cutting body and waveguide coupling layer4/n3), n4And n3Respectively cutting body is coupled with waveguide
The refractive index of layer.
2. unpolarized type narrow band optical filter according to claim 1, which is characterized in that the collimated incident beam is
Collimated light beam.
3. unpolarized type narrow band optical filter according to claim 1, which is characterized in that the both ends of the surface it is anti-reflection
The broad-band transparence-increased film layer that film layer is coated with for the central wavelength according to design.
4. unpolarized type narrow band optical filter according to claim 1, which is characterized in that the cylinder cutting body
Refractive Index of Material is higher than the refractive index of its two adjacent coupling layer.
5. unpolarized type narrow band optical filter described in one of -4 according to claim 1, which is characterized in that the plane
Optical waveguide, both sides external are the coupling layers of low-refraction, and middle layer is ducting layer, by the period film of height combination of refractive indices
Layer is again plus a high refractive index layer is constituted；Alternatively, the period film layer that ducting layer is combined by low high refractive index adds a low-refraction again
Film layer is constituted；The refractive index of ducting layer is higher than the coupling layer refractive index of two sides.
6. unpolarized type narrow band optical filter according to claim 5, which is characterized in that the cylinder be cylindrical body or
Square body；When cylinder is cylindrical body, section is ellipse, and when cylinder is square body, section is rectangle.
7. unpolarized type narrow band optical filter according to claim 5, which is characterized in that described two low-refractions
The ducting layer of coupling layer and high refractive index, period film layer, in comparison both high and low refractive index is.
8. unpolarized type narrow band optical filter according to claim 7, which is characterized in that the low-index film
Material is air, or for uniformly and treat the transparent gas of filter section, liquid or solid.
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| CN201811085460.3A CN109164526A (en) | 2018-09-18 | 2018-09-18 | A kind of unpolarized type narrow-band optical bandpass filter |
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| CN201811085460.3A CN109164526A (en) | 2018-09-18 | 2018-09-18 | A kind of unpolarized type narrow-band optical bandpass filter |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109445024A (en) * | 2018-12-22 | 2019-03-08 | 复旦大学 | A kind of optical band pass filter of flat-top banding pattern |
| CN114265145A (en) * | 2021-12-28 | 2022-04-01 | 复旦大学 | Optical band-pass filter with different polarization bandwidths |
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| CN202758091U (en) * | 2012-07-31 | 2013-02-27 | 杭州科汀光学技术有限公司 | Optical filter |
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| CN106019485A (en) * | 2016-05-31 | 2016-10-12 | 复旦大学 | Narrow band optical filter based on prism coupling guided-mode resonance |
| CN106896450A (en) * | 2017-03-27 | 2017-06-27 | 复旦大学 | A kind of many passband poles narrow band optical filter based on prism-coupled |
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2018
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Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN202758091U (en) * | 2012-07-31 | 2013-02-27 | 杭州科汀光学技术有限公司 | Optical filter |
| CN103197450A (en) * | 2013-04-11 | 2013-07-10 | 上海理工大学 | Polarization-independent filter based on guided-mode resonance liquid crystal structure |
| CN106019485A (en) * | 2016-05-31 | 2016-10-12 | 复旦大学 | Narrow band optical filter based on prism coupling guided-mode resonance |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109445024A (en) * | 2018-12-22 | 2019-03-08 | 复旦大学 | A kind of optical band pass filter of flat-top banding pattern |
| CN109445024B (en) * | 2018-12-22 | 2021-10-26 | 复旦大学 | Flat-top-band type optical band-pass filter |
| CN114265145A (en) * | 2021-12-28 | 2022-04-01 | 复旦大学 | Optical band-pass filter with different polarization bandwidths |
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