CN105093570A - Optical filter insensitive to temperature and device - Google Patents

Optical filter insensitive to temperature and device Download PDF

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Publication number
CN105093570A
CN105093570A CN201510543438.9A CN201510543438A CN105093570A CN 105093570 A CN105093570 A CN 105093570A CN 201510543438 A CN201510543438 A CN 201510543438A CN 105093570 A CN105093570 A CN 105093570A
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shifter
waveguide
phase
level
optical filter
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CN105093570B (en
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周治平
邓清中
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Beijing Aijie Photoelectric Technology Co., Ltd.
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Peking University
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    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/03—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on ceramics or electro-optical crystals, e.g. exhibiting Pockels effect or Kerr effect
    • G02F1/035—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on ceramics or electro-optical crystals, e.g. exhibiting Pockels effect or Kerr effect in an optical waveguide structure
    • G02F1/0353—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on ceramics or electro-optical crystals, e.g. exhibiting Pockels effect or Kerr effect in an optical waveguide structure involving an electro-optic TE-TM mode conversion

Abstract

The invention provides an optical filter insensitive to temperature and a device. The filter comprises three-level couplers and two-level phase shifters. The signal input end of the first-level coupler serves as the signal input end of the optical filter, and the signal output end of the first-level coupler is connected to the signal input end of the first-level phase shifter. The signal input end of the second-level coupler is connected to the signal output end of the first-level phase shifter, and the signal output end of the second-level coupler is connected to the signal input end of the second-level phase shifter. The signal input end of the third-level coupler is connected to the signal output end of the second-level phase shifter, and the signal output end of the third-level coupler serves as the signal output end of the optical filter. The first-level phase shifter and the second-level phase shifter are each formed by combining at least two waveguide structures and each comprises two pieces of optical waveguide. By the adoption of the optical filter and the device, the characteristics of flattop filtering can be kept while optical filter working channel drift caused by temperature changes can be greatly lowered.

Description

Temperature-resistant optical filter and device
Technical field
The present invention relates to integrated opto-electronic technical field, particularly relate to a kind of temperature-resistant optical filter and device.
Background technology
Optical filter (Opticalfilter) is the critical function device in integrated optoelectronic system, can be used for building the Wavelength-division multiplexer/demultiplexer in optical WDM communication system.Mach-zehnder type optical filter is a kind of conventional optical filter structure, is made up of input coupling beam divider, phase-shifter and output coupling bundling device.Because Mach-zehnder type optical filter has the frequency transmission spectrum of sinusoidal pattern, make the crosstalk of adjacent channel during wavelength-division multiplex larger.Adopt N level phase-shifter to obtain the frequency transmission spectrum of flat-top filtering characteristic by the multistage Mach-Zehnder interference structure that N+1 coupling mechanism cascade is formed for this reason.(A90nmCMOSIntegratedNano-PhotonicsTechnologyfor25GbpsWDMO pticalCommunicationsApplications) acquisition application in the 25Gbps wavelength-division multiplex optical interconnection system of IBM issue of this multistage Mach-Zehnder interference structure.
Because great majority all have certain thermo-optic effect for the photoelectron material (as silicon, silicon dioxide, indium phosphide) building optical filter, namely the refractive index of material can change along with the change of temperature.This thermo-optic effect can cause the operation wavelength of optical filter to be drifted about along with the change of temperature.For this reason, people in the industry proposes to prepare temperature-resistant Mach-Zehnder interfere type optical filter, and such as, the first scheme adopts negative thermo-optical coeffecient material as the top covering of waveguide; First scheme adopts the mode of width slab waveguide combination to build phase-shifter, and the third scheme is in two waveguides of phase-shifter, introduce the waveguide mode of different polarization.This several scheme can realize temperature-insensitive characteristic, but all cannot apply in actual production.Reason is in the first scheme: conventional negative thermo-optical coeffecient material and existing micro-nano technique incompatible; In alternative plan: the narrow waveguide loss of the mode wherein existing processes of width slab waveguide combination is too large; In third program: different polarization states assembled scheme needs to introduce the polarization rotator on sheet, but on current sheet, polarization rotator process allowance performance is all very poor.For this reason, how to provide a kind of to existing process compatible, and temperature-resistant optical filter can be realized become the current technical issues that need to address.
Summary of the invention
One of them object of the present invention is to provide a kind of temperature-resistant optical filter and device, and the technical matters of drifting about occurs along with the change of temperature with the operation wavelength solving the optical filter caused by thermo-optic effect.
For achieving the above object, first aspect, embodiments provides a kind of temperature-resistant optical filter, comprising: three grade coupled devices and two-stage phase-shifter, wherein:
The signal input part of first order coupling mechanism is as the signal input part of optical filter, and signal output part is connected to the signal input part of first order phase-shifter;
The signal input part of second level coupling mechanism is connected to the signal output part of described first order phase-shifter, and signal output part is connected to the signal input part of second level phase-shifter;
The signal input part of third level coupling mechanism is connected to the signal output part of described second level phase-shifter, and signal output part is as the signal output part of optical filter;
Described first order phase-shifter and described second level phase-shifter combine by least two kinds of waveguiding structures;
Described first order phase-shifter and described second level phase-shifter include two optical waveguides.
Alternatively, first order coupling mechanism comprises one or two signal input port, is connected respectively with the first port and/or the second port; Third level coupling mechanism comprises one or two signal output port, is connected respectively with the 3rd port and/or the 4th port.
Alternatively, in the phase-shifter of the described second level, the optical path difference of two Luciola substriata is 2 times of two Luciola substriata optical path differences in described first order phase-shifter; Or, in the phase-shifter of the described second level optical path difference of two Luciola substriata increase or reduce be no more than an operation wavelength length after be 2 times of described first order phase-shifter two Luciola substriata optical path difference;
Or the optical path difference of two Luciola substriata is 2 times of two Luciola substriata optical path differences in the phase-shifter of the described second level in described first order phase-shifter; Or, in the described first order phase-shifter optical path difference of two Luciola substriata increase or reduce be no more than an operation wavelength length after be 2 times of described second level phase-shifter two Luciola substriata optical path difference.
Alternatively, selected in described first order phase-shifter and described second level phase-shifter two kinds or two or more waveguiding structures are two kinds or two or more type in slab waveguide, channel waveguide, ridge waveguide and bar shaped-raceway groove Hybrid waveguide;
Or,
Two kinds selected in described first order phase-shifter and described second level phase-shifter or two or more waveguiding structures are any one in slab waveguide, channel waveguide, ridge waveguide and bar shaped-raceway groove Hybrid waveguide, and these two kinds or two or more waveguiding structures are of different sizes parameter.
Alternatively, the waveguide in first order phase-shifter and second level phase-shifter adopts slab waveguide and bar shaped-raceway groove Hybrid waveguide to combine; And slab waveguide adopts waveguide mode converter to be connected with bar shaped-raceway groove Hybrid waveguide.
Alternatively, the length difference of the two type waveguides comprised in first order phase-shifter and second level phase-shifter is: Δ L i, Δ L iI; The available heat backscatter extinction logarithmic ratio corresponding respectively with two type waveguides meet
Alternatively, described waveguide mode converter is multi-mode interference-type waveguide mode converter; This multi-mode interference-type waveguide mode converter comprises: the bar shaped-raceway groove Hybrid waveguide region of multimode waveguide region, width gradual change;
Wherein, the one end in described multimode waveguide region is for connecting slab waveguide, and the other end connects a Waveguide end face in the bar shaped-raceway groove Hybrid waveguide region of described width gradual change; Another Waveguide end face in the bar shaped-raceway groove Hybrid waveguide region of described width gradual change for connecting bar shaped-raceway groove Hybrid waveguide, the raceway groove in the bar shaped-raceway groove Hybrid waveguide region of described width gradual change and the raceway groove one_to_one corresponding of described bar shaped-raceway groove Hybrid waveguide.
Alternatively, the surface plasma waveguide that described temperature-resistant optical filter adopts poor conductor material waveguide or poor conductor material surface to cover layer of metal is made.
Alternatively, described poor conductor material is silicon dioxide, titania, gallium oxide, silicon, germanium, silicon nitride, indium phosphide or gallium nitride.
Second aspect, the embodiment of the present invention additionally provides a kind of temperature-resistant optical filtering apparatus, is made up of multiple temperature-resistant optical filter cascade mentioned above, wherein:
The output port of upper level optical filter is connected with the input port of next stage optical filter.
The temperature-resistant optical filter of the one that the embodiment of the present invention provides and device, slab waveguide and bar shaped-raceway groove hybrid waveguide is utilized to form multiple phase-shifter, by arranging the waveguide length of two types, second level phase-shifter is made to become preset relation with the phase differential of first order phase-shifter, and then the optical filter working channel drift making temperature-resistant optical filter provided by the invention significantly can reduce temperature variation while keeping flat-top filtering characteristic to cause.In addition, in the temperature-resistant optical filter structure that the embodiment of the present invention provides, the minimum feature that need process can >=200nm, low and middle-end 0.18 μm of micro-nano technology technique of universal commercialization at present can be adopted to complete batch machining produce, there is the feature of low cost, in integrated opto-electronic field, there is very high using value.
Accompanying drawing explanation
Can understanding the features and advantages of the present invention clearly by reference to accompanying drawing, accompanying drawing is schematic and should not be construed as and carry out any restriction to the present invention, in the accompanying drawings:
Fig. 1 is the temperature-resistant optical filter structural representation of one that one embodiment of the invention provides;
Fig. 2 is the schematic cross-section of the slab waveguide that provides of one embodiment of the invention and bar shaped-raceway groove Hybrid waveguide;
Fig. 3 is that the light field flux-density distribution of slab waveguide shown in Fig. 2 and bar shaped-raceway groove Hybrid waveguide contrasts schematic diagram;
Fig. 4 is the waveguide mode converter structure schematic diagram that one embodiment of the invention provides;
Fig. 5 is the multi-channel operation wavelength with temperature drift value comparative analysis schematic diagram of the temperature-resistant optical filter that provides of one embodiment of the invention and conventional multi-level Mach-zehnder type optical filter;
Fig. 6 is the method for designing block diagram to the temperature-resistant optical filter shown in Fig. 1;
Fig. 7 is a kind of temperature-insensitive optical filtering apparatus structural representation that another embodiment of the present invention provides;
Fig. 8 be Fig. 7 the channel width distribution schematic diagram of temperature-insensitive optical filtering apparatus is provided.
Embodiment
Below in conjunction with drawings and Examples, the specific embodiment of the present invention is described in further detail.Following examples for illustration of the present invention, but are not used for limiting the scope of the invention.
Embodiment one
Embodiments provide a kind of temperature-resistant optical filter, as shown in Figure 1, comprising: three grade coupled devices and two-stage phase-shifter, wherein:
First signal input part of first order coupling mechanism 3 is connected to the first port one, and secondary signal input end is connected to the second port 2, and signal output part is connected to the signal input part of first order phase-shifter 4;
The signal input part of second level coupling mechanism 5 is connected to the signal output part of first order phase-shifter 4, and signal output part is connected to the signal input part of second level phase-shifter 6;
The signal input part of third level coupling mechanism 7 is connected to the signal output part of second level phase-shifter 6, and the first signal output part is connected to the 3rd port 8, and secondary signal output terminal is connected to the 4th port 9;
First order phase-shifter 4 is made up of the bar shaped-raceway groove hybrid waveguide shown in slab waveguide shown on the left of Fig. 2 and right side with second level phase-shifter 6, adopts waveguide mode converter to be connected between slab waveguide with bar shaped-raceway groove hybrid waveguide.
The temperature-resistant optical filter of the one that the embodiment of the present invention provides, slab waveguide and bar shaped-raceway groove hybrid waveguide is utilized to form multiple phase-shifter, by arranging the waveguide length of two types, second level phase-shifter is made to become preset relation with the phase differential of first order phase-shifter, and then make temperature-resistant optical filter provided by the invention, while keeping flat-top filtering characteristic, significantly can reduce the optical filter multi-channel operation wave length shift that temperature variation causes.
In the embodiment of the present invention, two kinds selected in first order phase-shifter and second level phase-shifter in first order phase-shifter and second level phase-shifter or two or more waveguiding structures are two kinds or two or more type in slab waveguide, channel waveguide, ridge waveguide and bar shaped-raceway groove Hybrid waveguide; Or, two kinds selected in first order phase-shifter and second level phase-shifter or two or more waveguiding structures are any one in slab waveguide, channel waveguide, ridge waveguide and bar shaped-raceway groove Hybrid waveguide, and these two kinds or two or more waveguiding structures are of different sizes parameter.
In the embodiment of the present invention, waveguide mode converter adopts multi-mode interference-type waveguide mode converter 200 as shown in Figure 4.This multi-mode interference-type waveguide mode converter 200 comprises the bar shaped-raceway groove Hybrid waveguide region 202 of multimode waveguide region 201 and width gradual change.Wherein, the one end in multimode waveguide region 201 is for connecting slab waveguide 100, and the other end connects a Waveguide end face in the bar shaped-raceway groove Hybrid waveguide region 202 of width gradual change.Another Waveguide end face in the bar shaped-raceway groove Hybrid waveguide region 202 of width gradual change for connecting bar shaped-raceway groove Hybrid waveguide 300, the raceway groove one_to_one corresponding of raceway groove in the bar shaped-raceway groove Hybrid waveguide region 202 of width gradual change 203 and bar shaped-raceway groove Hybrid waveguide 300.
In the embodiment of the present invention, succinct for designing, alternatively, first order coupling mechanism 3, second level coupling mechanism 5 and third level coupling mechanism 7 have identical duct width and coupling space.
In practical application, for convenience of adopting phase shift elementary cell to build phase-shifter, do not destroy the flat-top filtering characteristics of phase-shifter, alternatively, in the phase-shifter of the second level, the optical path difference of two Luciola substriata is 2 times of two Luciola substriata optical path differences in first order phase-shifter; Or, in the phase-shifter of the second level optical path difference of two Luciola substriata increase or reduce be no more than an operation wavelength length after be 2 times of first order phase-shifter two Luciola substriata optical path difference; Or the optical path difference of two Luciola substriata is 2 times of two Luciola substriata optical path differences in the phase-shifter of the second level in first order phase-shifter; Or, in the first order phase-shifter optical path difference of two Luciola substriata increase or reduce be no more than an operation wavelength length after be 2 times of second level phase-shifter two Luciola substriata optical path difference.
Alternatively, the surface plasma waveguide that first order phase-shifter 4 and second level phase-shifter 6 adopt poor conductor material waveguide or poor conductor material surface to cover layer of metal is made.Wherein, poor conductor material is dielectric, semiconductor or organism.Such as, dielectric is silicon dioxide, titania or gallium oxide; Semiconductor is three or five race's photoelectron compound-materials of silicon, germanium, silicon nitride or similar indium phosphide or gallium nitride.Surface plasma waveguide is: silicon or silica surface cover one deck silver or golden surface plasma waveguide.In practical application, the first port one and/or the second port 2 are input port, and the 3rd port 8 and/or the 4th port 9 are output port.Those skilled in the art can select as the case may be.
Embodiment two
For embodying the superiority of a kind of temperature-resistant optical filter that the embodiment of the present invention provides further, the embodiment of the present invention additionally provides a kind of method for designing of temperature-resistant optical filter, as shown in Figure 6, comprising:
S1, respectively calculate selected by the effective refractive index of at least two kinds of waveguiding structures, and obtain available heat backscatter extinction logarithmic ratio and the group index of often kind of waveguiding structure;
S2, obtain group's optical path difference according to the Free Spectral Range of required optical filter and centre wavelength;
S3, obtain the length difference of at least two kinds of waveguides in phase-shifter according to available heat backscatter extinction logarithmic ratio and group index;
The loss value of S4, basis at least two waveguides to obtain the ratio of the luminous power transmission coefficient of corresponding phase-shifter, and then obtains the coupling length of coupling mechanism at different levels.
In practical application, the order of step S1 and step S2 can be exchanged, or carries out simultaneously.Those skilled in the art can set as the case may be, and the present invention is not construed as limiting.
Below in conjunction with accompanying drawing and embodiment, the method for designing to the temperature-resistant optical filter that the embodiment of the present invention provides is described in further detail.
As shown in Figure 1, the temperature-resistant optical filter provided in the present embodiment has two-stage Mach-Zehnder interfere type structure, comprising: the first port one, the second port 2, first order coupling mechanism 3, first order phase-shifter 4, second level coupling mechanism 5, second level phase-shifter 6, third level coupling mechanism 7, the 3rd port 8 and the 4th port 9.
Wherein, the optical phase difference (namely in Fig. 1, on the upside of first order phase-shifter 4, waveguide optical phase place deducts downside waveguide optical phase place) of two waveguides in first order phase-shifter 4 is φ=(OL on-OL under) 2 π/λ, in formula, OL represents the optical length of corresponding waveguide.The optical phase difference (in Fig. 1, the downside waveguide optical phase differential of second level phase-shifter 6 deducts side waveguide phase differential) of two waveguides in second level phase-shifter 6 is 2 φ.Then from the first port one or the second port 2 input signal, the luminous power transmission spectrum Tr that the 3rd port 8 or the 4th port 9 export 1all can write:
Tr 1＝|A 0+A 1exp(-jφ)+A 2exp(-j2φ)+A 3exp(-j3φ)| 2(1)
In formula, A 0, A 1, A 2, A 3for the superposition coefficient of luminous power.Exp () for natural constant e be the exponential function at the end.If the optical path difference of first order phase-shifter is 2 times of second level phase-shifter optical path difference, corresponding transmission spectrum expression formula is still such as formula shown in (1), and difference is only that the concrete numerical value superposing coefficient can be different.Thus in mobile only for 2 times of expansion that second level phase-shifter optical path difference is the first order, but the method set forth has general meaning for above-mentioned two kinds of situations.
From formula (1), the luminous power transmission spectrum of the wave filter that the embodiment of the present invention provides is similar to the finite term superposition of Fourier transform, thus chooses suitable superposition coefficient A 0, A 1, A 2, A 3just the transmission spectrum of flat characteristic can be obtained.In practical application, A 0=-0.3652, A 1=0.5715, A 2=-0.1685, A 3=-0.1077 is one group of coefficient that can obtain flat-top transport property, and the embodiment of the present invention processes with these group data.
In the embodiment of the present invention, three grade coupled devices all adopt directional coupler to build, and use L 1, L 2, L 3distribution represents the coupling length of coupling mechanism 3, second level coupling mechanism 5 and third level coupling mechanism 7.For designing conveniently, alternatively, three grade coupled utensils have identical duct width and coupling space, therefore have identical unit length mutual coupling factor k.According to coupled mode theory, the A in formula (1) can be expressed as
A 0 = - sin ( kL 1 ) sin ( kL 2 ) cos ( kL 3 ) A 1 = a · cos ( kL 1 ) cos ( kL 2 ) cos ( kL 3 ) A 2 = - a 2 · sin ( kL 1 ) cos ( kL 2 ) sin ( kL 3 ) A 3 = - a 3 · cos ( kL 1 ) sin ( kL 2 ) sin ( kL 3 ) - - - ( 2 )
In formula (2), a to represent in first order phase-shifter 4 ratio of side waveguide and downside Waveguide power transmission factor, a 2represent the ratio of lower side waveguide and upside Waveguide power transmission factor in second level phase-shifter 6.Process is carried out to formula (2) formula (3) can be obtained:
L 1 = k - 1 · a r c t a n ( a | A 0 A 2 A 1 A 3 | ) L 2 = k - 1 · a r c t a n ( | A 0 A 3 A 1 A 2 | ) L 3 = k - 1 · a r c t a n ( a - 2 | A 2 A 3 A 0 A 1 | ) - - - ( 3 )
Known according to formula (2) and formula (3), as long as determine a of first order phase-shifter 4 correspondence, required coupler length at different levels can be drawn according to formula (3).
In practical application, the temperature dependency due to phase differential causes the temperature variant main cause of filter channel work waveguide, therefore, the method for designing of phase-shifter is discussed below.
To the optical phase difference φ=(OL of two waveguides in first order phase-shifter 4 on-OL under) 2 π/λ analyze further and can obtain formula (4):
In formula, n effrepresent the effective refractive index of waveguide, Δ L represents the length difference of upper side waveguide and lower side waveguide in first order phase-shifter 4; And using subscript I, II represents slab waveguide and bar shaped-raceway groove hybrid waveguide respectively.
Temperature dependency according to above formula φ can be expressed as,
∂ φ ∂ T = ( ∂ n e f f I ∂ T · ΔL I + ∂ n e f f I I ∂ T · ΔL I I ) · 2 π λ - - - ( 5 )
From formula (5), if select the waveguide length differences of two kinds in phase-shifter to meet
∂ n e f f I / ∂ T · ΔL I + ∂ n e f f I I / ∂ T · ΔL I I = 0 - - - ( 6 )
The temperature dependency of φ can be eliminated, realize the optical filter of temperature-insensitive.
Utilize formula (6) that the length difference of two kind waveguides can't be determined completely, also need the wave filter Free Spectral Range λ needed for reality fSRand central wavelength lambda cconvolution (7) determines crowd optical path difference Δ OL g:
λ F S R = λ c 2 ΔOL g - - - ( 7 )
Wherein, group's optical path difference Δ OL gcan be expressed as again
ΔOL g = n g I · ΔL I + n g I I · ΔL I I - - - ( 8 )
In formula, for group index, subscript I, II represent slab waveguide and bar shaped-raceway groove hybrid waveguide respectively.
In the present embodiment, the principle of work of this wave filter when the first port one that describe only when temperature-resistant optical filter is input port, the 3rd port 8 is output terminal, analytical approach when other input/output end ports combine mutually is similar, and the present invention has repeated no longer one by one.
In practical application, during temperature-resistant optical filter corresponding according to polytype waveguide design, Chinese style (4) has effective refractive index corresponding to the waveguide region identical with waveguide type quantity, group index and length difference equation to formula (8) above.Analytic process is identical with the waveguide design process comprising two types, and the present invention has repeated no longer one by one.
Embodiment three
According to the method for embodiment two, the present embodiment is with the first port one for input port, and the 3rd port 8 and the 4th port 9 are output port.First order phase-shifter 4 and second level phase-shifter 6 select the waveguide of slab waveguide and bar shaped-raceway groove hybrid waveguide two type to form.As shown in Figure 2, waveguide material comprises the silicon waveguide that top covering and substrate are all silicon dioxide, and the light field flux-density distribution of slab waveguide and bar shaped-raceway groove hybrid waveguide as shown in Figure 3.Wherein duct thickness is 220nm, slab waveguide width is 450nm, and in directional coupler, two waveguide spacing are 200nm, and bar shaped-raceway groove hybrid waveguide overall width is 600nm, raceway groove is positioned at channel waveguide center and width is 200nm, is 60nm by the thickness of filled with silicon material in raceway groove.
Larger difference is there is by the structure of Fig. 2 and Fig. 3 these two kinds of waveguides visible and light field flux-density distribution, thus also there is larger difference in their fundamental performance parameter, as shown in table 1, the effective refractive index of slab waveguide and bar shaped-raceway groove hybrid waveguide, group index and available heat backscatter extinction logarithmic ratio.
The parameter list of table 1 slab waveguide and bar shaped-raceway groove hybrid waveguide
In the embodiment of the present invention, slab waveguide and bar shaped-raceway groove hybrid waveguide adopt the waveguide mode converter shown in Fig. 4 to be connected, wherein waveguide mode converter length L=5 μm; Multiple-mode interfence peak width Wmmi=1.25 μm, length Lmmi=1.40 μm.
Wavelength centered by 1550nm, and design for the channel spacing of 400GHz, corresponding Free Spectral Range λ fSR=6.4nm.By above-mentioned waveguide parameter, required group's optical path difference Δ OL g=375.39 μm.Corresponding Δ L slot=603.76 μm, Δ L strip=-352.07 μm.Wherein Δ L stripthe slab waveguide comprised for side waveguide lower in negative number representation first order phase-shifter 4 is longer than the slab waveguide comprised in upper side waveguide.
In the embodiment of the present invention, phase-shifter adopts modular phase shift elementary cell to build, namely minimum phase difference required in whole wave filter is selected to be phase shift elementary cell, phase-shifter at different levels is made up of the phase differential unit of varying number, as first order phase-shifter 4 comprises a phase differential unit, second level phase-shifter 6 comprises two phase shift elementary cells.The benefit of modular design is adopted to be: if fabrication error causes the phase differential off-design value of phase-shifter, as long as but the homogeneity of technique is good, so two waveguide phase differential of second level phase-shifter 6 still can remain 2 times of first order phase-shifter 4, thus can not destroy its flat-top filtering characteristic.
In practical application, slab waveguide loss is 4dB/cm, bar shaped-raceway groove hybrid waveguide loss is 10dB/cm, thus corresponding a=0.8987 in first order phase-shifter 4 can be obtained, the coupling length that substitution formula (3) can obtain coupling mechanism 3, second level coupling mechanism 5 and third level coupling mechanism 7 is followed successively by 8.74 μm, 6.28 μm and 2.99 μm.
According to above-mentioned design parameter, simulation result in conjunction with Finite Element Method can be calculated the luminous power transmission spectrum of temperature-resistant optical filter provided by the present invention as shown in part A in Fig. 5, wherein channel one represents the Output rusults of the 3rd port 8, and channel two represents the Output rusults of the 4th port 9.As seen from the figure, the optical filter that the embodiment of the present invention provides shows flat-top filtering characteristic, simultaneously the operation wavelength of its channel not variation with temperature and changing.As a comparison, be also provided with tradition 2 grades of Mach-Zehnder interfere type wave filter comparative examples in the embodiment of the present invention, the phase-shifter in this tradition 2 grades of Mach-Zehnder interfere type wave filters is only containing slab waveguide.From part B in Fig. 5, the drift value of tradition 2 grades of Mach-Zehnder interfere type filter channel center wavelength with temperature is about 75pm/ DEG C, and the functional reliability impact of temperature on traditional array waveguide optical grating is very large as can be seen here.
Optical filter provided by the invention has the flat-top filtering characteristic of temperature-insensitive, while keeping flat-top filtering characteristic, namely significantly can reduce the filter working wavelength drift that temperature variation causes.And, temperature-resistant optical filter provided by the invention requires low to processing technology, need in structure process minimum feature can >=200nm, therefore adopt low and middle-end 0.18 μm of micro-nano technology technique of universal commercialization at present can complete batch machining to produce, thus reduce production cost.
Embodiment four
The embodiment of the present invention further provides a kind of temperature-resistant optical filtering apparatus, and be made up of multiple temperature-resistant optical filter cascade, namely the output port of upper level optical filter is connected with the input port of next stage optical filter.Wherein, the residue end of most previous stage optical filter is as the signal input part (or signal output part) of this optical filtering apparatus, and the residue end of afterbody optical filter is as the signal output part (or signal input part) of this optical filtering apparatus.
Temperature-resistant optical filter provided by the invention also has good scalability, can expand to the optical filtering apparatus of multi output port.As shown in Figure 7, to be designed to basic structural unit in embodiment one, to design the filter of 2 kinds of free light wave scopes of difference, then it is carried out by Fig. 7 the temperature-insensitive optical filtering apparatus that cascade just can obtain 4 channels.Wherein the Free Spectral Range of first order wave filter FIR1 is 6.4 μm, and in the wave filter of the second level, the Free Spectral Range of FIR22 is 2 times of the first order, is 12.8 μm.Meanwhile, the optical phase difference (φ in the derivation of embodiment two method for designing) of wave filter FIR21 is relative to the many pi/2s of the optical phase difference of wave filter FIR22.Modular optical path difference elementary cell is adopted as the design in embodiment three, the optical path difference of the first order phase-shifter of selecting filter FIR22 is elementary cell, then all phase-shifters in first order wave filter FIR1 and wave filter FIR22 are an integer optical path difference elementary cell composition.By above-mentioned optical path difference elementary cell, phase shift elementary cell in the wave filter FIR21 of the second level adds that 1.55 μm/4 optical path differences are formed.
Utilize said method, optical filter can be expanded to the optical filtering apparatus comprising 4 channels as shown in Figure 7 by the embodiment of the present invention.This optical filtering apparatus shows flat-top filtering characteristic, and the luminous power transmission spectrum of 4 channels as shown in Figure 8.
Certainly, those skilled in the art can according to embody rule, and further cascade can obtain the optical filtering apparatus of more channels, does not repeat them here.
In sum, the temperature-resistant optical filter that the embodiment of the present invention provides and device, this optical filter has the flat-top filtering characteristic of temperature-insensitive, while keeping flat-top filtering characteristic, namely significantly can reduce the operation wavelength drift that temperature variation causes.And, this temperature-resistant optical filter requires low to processing technology, need in structure the minimum feature of processing can >=200nm, universal commercial low and middle-end 0.18 μm of micro-nano technology technique can be adopted to complete batch machining and to produce, can production cost be reduced.
In the present invention, term " first ", " second ", " the 3rd " only for describing object, and can not be interpreted as instruction or hint relative importance.Term " multiple " refers to two or more, unless otherwise clear and definite restriction.
Although describe embodiments of the present invention by reference to the accompanying drawings, but those skilled in the art can make various modifications and variations without departing from the spirit and scope of the present invention, such amendment and modification all fall into by within claims limited range.

Claims (10)

1. a temperature-resistant optical filter, is characterized in that, comprising: three grade coupled devices and two-stage phase-shifter, wherein:
The signal input part of first order coupling mechanism is as the signal input part of optical filter, and signal output part is connected to the signal input part of first order phase-shifter;
The signal input part of second level coupling mechanism is connected to the signal output part of described first order phase-shifter, and signal output part is connected to the signal input part of second level phase-shifter;
The signal input part of third level coupling mechanism is connected to the signal output part of described second level phase-shifter, and signal output part is as the signal output part of optical filter;
Described first order phase-shifter and described second level phase-shifter combine by least two kinds of waveguiding structures;
Described first order phase-shifter and described second level phase-shifter include two optical waveguides.
2. temperature-resistant optical filter according to claim 1, is characterized in that, first order coupling mechanism comprises one or two signal input port, is connected respectively with the first port and/or the second port; Third level coupling mechanism comprises one or two signal output port, is connected respectively with the 3rd port and/or the 4th port.
3. temperature-resistant optical filter according to claim 1, is characterized in that, in the phase-shifter of the described second level, the optical path difference of two Luciola substriata is 2 times of two Luciola substriata optical path differences in described first order phase-shifter; Or, in the phase-shifter of the described second level optical path difference of two Luciola substriata increase or reduce be no more than an operation wavelength length after be 2 times of described first order phase-shifter two Luciola substriata optical path difference;
Or,
In described first order phase-shifter, the optical path difference of two Luciola substriata is 2 times of two Luciola substriata optical path differences in the phase-shifter of the described second level; Or, in the described first order phase-shifter optical path difference of two Luciola substriata increase or reduce be no more than an operation wavelength length after be 2 times of described second level phase-shifter two Luciola substriata optical path difference.
4. temperature-resistant optical filter according to claim 3, it is characterized in that, two kinds selected in described first order phase-shifter and described second level phase-shifter or two or more waveguiding structures are two kinds or two or more type in slab waveguide, channel waveguide, ridge waveguide and bar shaped-raceway groove Hybrid waveguide;
Or,
Two kinds selected in described first order phase-shifter and described second level phase-shifter or two or more waveguiding structures are any one in slab waveguide, channel waveguide, ridge waveguide and bar shaped-raceway groove Hybrid waveguide, and these two kinds or two or more waveguiding structures are of different sizes parameter.
5. temperature-resistant optical filter according to claim 4, is characterized in that, the waveguide in first order phase-shifter and second level phase-shifter adopts slab waveguide and bar shaped-raceway groove Hybrid waveguide to combine; And slab waveguide adopts waveguide mode converter to be connected with bar shaped-raceway groove Hybrid waveguide.
6., according to the temperature-resistant optical filter of claim 4, it is characterized in that,
The length difference of the two type waveguides comprised in first order phase-shifter and second level phase-shifter is: Δ L i, Δ L iI; The available heat backscatter extinction logarithmic ratio corresponding respectively with two type waveguides meet ΔL I · ∂ n e f f I / ∂ T + ΔL I I · ∂ n e f f I I / ∂ T = 0.
7. according to the temperature-resistant optical filter of claim 5, it is characterized in that, described waveguide mode converter is multi-mode interference-type waveguide mode converter;
This multi-mode interference-type waveguide mode converter comprises: the bar shaped-raceway groove Hybrid waveguide region of multimode waveguide region, width gradual change;
Wherein, the one end in described multimode waveguide region is for connecting slab waveguide, and the other end connects a Waveguide end face in the bar shaped-raceway groove Hybrid waveguide region of described width gradual change; Another Waveguide end face in the bar shaped-raceway groove Hybrid waveguide region of described width gradual change for connecting bar shaped-raceway groove Hybrid waveguide, the raceway groove in the bar shaped-raceway groove Hybrid waveguide region of described width gradual change and the raceway groove one_to_one corresponding of described bar shaped-raceway groove Hybrid waveguide.
8. temperature-resistant optical filter according to claim 1, is characterized in that,
The surface plasma waveguide that described temperature-resistant optical filter adopts poor conductor material waveguide or poor conductor material surface to cover layer of metal is made.
9. temperature-resistant optical filter according to claim 8, is characterized in that,
Described poor conductor material is silicon dioxide, titania, gallium oxide, silicon, germanium, silicon nitride, indium phosphide or gallium nitride.
10. a temperature-resistant optical filtering apparatus, is characterized in that, is made up of the temperature-resistant optical filter cascade described in multiple claim 1 to 9 any one, wherein:
The output port of upper level optical filter is connected with the input port of next stage optical filter.
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