CN103869510A - Tunable filtering structure and filter - Google Patents
Tunable filtering structure and filter Download PDFInfo
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- CN103869510A CN103869510A CN201210549782.5A CN201210549782A CN103869510A CN 103869510 A CN103869510 A CN 103869510A CN 201210549782 A CN201210549782 A CN 201210549782A CN 103869510 A CN103869510 A CN 103869510A
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Abstract
The invention relates to the optical filtering field and discloses a tunable filtering structure. The tunable filtering structure comprises two optical elements, wherein the two opposite surfaces of the two optical elements are parallel to each other and a liquid crystal layer is filled between the two surfaces, transparent electrodes are arranged between the liquid crystal layer and the two surfaces, respectively, and variable voltage is applied between the two transparent electrodes; the refractive indexes of the two optical elements both are greater than the refractive index of the liquid crystal layer. An incident light spectrum comprising a critical wavelength is divided into two sections of a long wavelength and a short wavelength by virtue of a phenomenon of total reflection of light which is incident into an optically thinner medium from an optically denser medium, the two sections of the long wavelength and the short wavelength are output in a total reflection mode and in a transmission mode, respectively, and the critical wavelength is changed by changing the refractive index of the liquid crystal layer of the optically thinner medium, and therefore, the tunable filtering structure is realized; two filtering structures are combined and cascaded, and then a band-pass filter tunable in both bandwidth position and width can be realized. The tunable filter is tunable in both bandwidth position and width, and also wide in tuning range, and simple and convenient to tune, and further capable of realizing narrowband flat-top band-pass filtering or wideband flat-top band-pass filtering.
Description
Technical field
The present invention relates to optically filtering field, the wave filter that relates in particular to a kind of adjustable filter structure and formed by this structure.
Background technology
Bandwidth adjustable filter is a kind of basic optical element, and it is essentially band flow-through wave filter, only allows specific wavelength signal to pass through, and other wavelength signals reflect away.It can be applied to the aspects such as take up and down/demodulation multiplexer of reconfigurable light path (ROADM) and cross interconnected (OXC) system of light and sensing network in dwdm system.As the gain tilt for offsetting image intensifer, thereby reduce the deviation of the interchannel of each receiving end optical signal power.
At present, main tunable optic filter has F-P wave filter, Mach-Zehnder wave filter, electro-optical filter, grating type wave filter and Fiber Bragg Grating FBG wave filter etc.Wherein, F-P wave filter includes nematic liquid crystal F-P wavelength tuning wave filter, utilize the electrooptical effect principle of liquid crystal, its structure is: on the inside surface of two glass substrates, plating has the dielectric mirror of high reflectance to its operating wavelength range, for making the consistent consistent alignment layer of direction of arranging of liquid crystal orientation used be plated on this dielectric mirror, liquid crystal is located between the consistent alignment layer of described two direction.This structure is by apply voltage in two dielectric mirror, to change the refractive index of liquid crystal layer, thereby changes the light path of incident light, controls the wavelength tuning performance of light transmision peak.The tuning tuning range by liquid crystal layer refractive index between F-P chamber of filter wavelength of this structure limits, and filter peak tunable wave length is limited in scope, and filtering bandwidth is non-adjustable.
Summary of the invention
For the problems referred to above, the wave filter that the present invention proposes a kind of adjustable filter structure and is made up of this structure, filtering wave band and filtering bandwidth are all tunable, and tuning range is wide.
For achieving the above object, the technical scheme that the present invention proposes is: a kind of adjustable filter structure, comprise the first optical element and the second optical element, described the first optical element and the second optical element have two apparent surfaces that are parallel to each other, and are respectively first surface and second surface; Filling liquid crystal layer between first surface and second surface, arranges respectively transparency electrode between liquid crystal layer and two surfaces, between two transparency electrodes, applies variable voltage; The refractive index of the first optical element and the second optical element is all greater than the refractive index of liquid crystal layer; Incident light is in the interphase light splitting of first surface and liquid crystal layer, and the optical wavelength that the angle of total reflection equals incident angle is critical wavelength, and the light that wavelength is more than or equal to critical wavelength is totally reflected output, and wavelength is less than the light transmission output of critical wavelength; Described critical wavelength changes with the variation of the variable voltage applying between two transparency electrodes.
Further, the logical light face of described first surface, second surface, the first optical element and the second optical element is all coated with full wave anti-reflection film.
Adjustable filter of the present invention, comprises two above-mentioned adjustable filter structures, is respectively first order filter structure and second level filter structure, and the critical wavelength of first order filter structure is λ
1, the critical wavelength of second level filter structure is λ
2, λ
1with λ
2unequal; Incident light passes through first order filter structure and second level filter structure successively, by second level filter structure output filtering light.
Further, the critical wavelength λ of described first order filter structure
1be greater than the critical wavelength λ of second level filter structure
2; Second level filter structure is located in the light path of first order filter structure transmitted light, and incident light is through first order filter structure, and the light of transmissive portion incides second level filter structure, and through the second level, filter structure total reflection part is output filtering light, and filtering bandwidth is λ
1-λ
2.
Or, the critical wavelength λ of described first order filter structure
1be less than the critical wavelength λ of second level filter structure
2; Second level filter structure is located in the light path of first order filter structure total reflection light, and incident light is through first order filter structure, and the light of total reflection part incides second level filter structure, is output filtering light through second level filter structure transmissive portion, and filtering bandwidth is λ
2-λ
1.
Beneficial effect of the present invention is: while utilizing light by optically denser medium incident optically thinner medium, produce the phenomenon of total reflection, the incident light spectrum that makes to comprise critical wavelength is divided into two sections of long wavelength and short wavelengths, total reflection output and transmission output respectively, change critical wavelength by the refractive index that changes optically thinner medium, realize filtering adjustable structure, in conjunction with two filter structures that critical wavelength is adjustable, realize bandpass filter, its bandwidth and passband position are all tunable, and tuning range is wide, tuning easy, can be easy to realize arrowband flat top belt pass filter or broadband flat top belt pass filter.
Accompanying drawing explanation
Fig. 1 is adjustable filter structure embodiment schematic diagram of the present invention;
Fig. 2 is adjustable filter embodiment mono-schematic diagram of the present invention;
Fig. 3 is adjustable filter embodiment bis-schematic diagram of the present invention;
Fig. 4 is adjustable filter filtering principle schematic diagram of the present invention.
Reference numeral: 1, the first optical element; 2, the second optical element; 3, liquid crystal layer; S1, first surface; S2, second surface; 100, first order filter structure; 200, second level filter structure.
Embodiment
Below in conjunction with the drawings and specific embodiments, the present invention will be further described.
The present invention produces total reflection phenomenon while utilizing light by optically denser medium incident optically thinner medium, to comprise critical wavelength λ 0(light and incide optically thinner medium by optically denser medium at an angle time, just can produce the wavelength of total reflection) spectrum segmentation, (wavelength is greater than the light of λ 0 to long wave part, under similarity condition, the critical angle of its total reflection is less than the critical angle of wavelength X 0) be totally reflected output, (wavelength is less than the light of λ 0 to shortwave part, under similarity condition, the critical angle of its total reflection is greater than the critical angle of wavelength X 0) be transmitted output.In the changeless situation of incident angle, by changing the refractive index of optically thinner medium, regulate critical wavelength, and then regulate the boundary wavelength of segmentation spectrum, regulate the position of filtering.
Concrete, be illustrated in figure 1 filter structure embodiment of the present invention, comprise the first optical element 1 and the second optical element 2, this first optical element 1 and the second optical element 2 have two apparent surfaces that are parallel to each other, and are respectively first surface S1 and second surface S2; Filling liquid crystal layer 3 between first surface S1 and second surface S2, arranges respectively transparency electrode between liquid crystal layer 3 and two surperficial S1, S2, applies variable voltage V between two transparency electrodes; The refractive index of the first optical element 1 and the second optical element 2 is all greater than the refractive index of liquid crystal layer 3; Incident light is in the interphase light splitting of first surface S1 and liquid crystal layer 3, and the optical wavelength that the angle of total reflection equals incident angle is critical wavelength, and the light that wavelength is more than or equal to critical wavelength is totally reflected output, and wavelength is less than the light transmission output of critical wavelength; Because the refractive index of optically thinner medium liquid crystal layer 3 changes with the voltage V loading between two transparency electrodes, in the constant situation of incident angle, the variations in refractive index of liquid crystal layer 3, critical wavelength also will change, therefore critical wavelength changes with the variation of the variable voltage V applying between two transparency electrodes, thereby realize the tunable function of filtering.Because liquid crystal layer 3 variations in refractive index can reach 15%, the moving range of critical wavelength is very large, therefore filtering tunable range is large.Wherein, the logical light face of first surface S1, second surface S2, the first optical element 1 and the second optical element 2 is all coated with full wave anti-reflection film, reduces the insertion loss of structure.Can be identical optical material as the first optical element 1 of optically denser medium and the second optical element 2, also can adopt different optical material, refractive index is all greater than the variations in refractive index scope of optically thinner medium liquid crystal layer 3, but the refractive index of two optical elements also can equate, also can not wait.Wherein, the angle of first surface S1 and first optical element 1 plane of incidence is γ, adjusts the size of the initial incidence angle θ of incident light by the size at design γ angle, thereby regulates the adjustable extent of critical wavelength.
In conjunction with two above-mentioned filter structure cascades, can realize all tunable bandpass filter of bandwidth location and width, concrete, embodiment mono-as shown in Figure 2, comprise two filter structures, be respectively first order filter structure 100 and second level filter structure 200, the critical wavelength of first order filter structure 100 is λ
1, the critical wavelength of second level filter structure 200 is λ
2, λ
1with λ
2unequal; Incident light passes through first order filter structure 100 and second level filter structure 200 successively, by second level filter structure 200 output filtering light.In this embodiment, the critical wavelength λ of first order filter structure 100
1be greater than the critical wavelength λ of second level filter structure 200
2; Second level filter structure 200 is located in the light path of first order filter structure 100 transmitted lights, incident light is through first order filter structure 100, the light of transmissive portion incides second level filter structure 200, is output filtering light through second level filter structure 200 total reflection parts, and filtering bandwidth is λ
1-λ
2.Be illustrated in figure 4 this filter filtering principle schematic, Fig. 4 (a) represents the transmitted light intensity ratio of first order filter structure 100, and in the time applying voltage V1 between two transparency electrodes at first order filter structure 100, its critical wavelength is λ
1therefore wavelength is more than or equal to λ
1light be all reflected output, wavelength is less than λ
1the equal transmission of light output.Apply voltage V2 between two transparency electrodes of second level filter structure 200 time, its critical wavelength is λ
2, wavelength is more than or equal to λ
2light all exported by its total reflection, wavelength is less than λ
2the equal transmission of light output, be the total reflection light intensity ratio of second level filter structure 200 as shown in Figure 4 (b).Second level filter structure 200 is placed in to the transmitted light path of first order filter structure 100, utilize the transmission wave band of first order filter structure 100 and the total reflection wave band of second level filter structure 200 to be combined filtering, can obtain bandpass filtering spectrum as shown in Figure 4 (c).That is, incident light is through 100 light splitting of first order filter structure, and the light of its transmissive portion incides second level filter structure 200, is output filtering light through second level filter structure 200 total reflection parts, and its filtering bandwidth is λ
1-λ
2.Put on voltage V1 and the V2 of transparency electrode by change, change the liquid crystal layer refractive index of first order filter structure 100 and second level filter structure 200, thereby regulate critical wavelength λ
1and λ
2, realize the tuber function of bandpass filter bandwidth width and bandwidth location.
As shown in Figure 3, for tunable optic filter embodiment bis-of the present invention, different from embodiment mono-, the critical wavelength λ of first order filter structure 100
1be less than the critical wavelength λ of second level filter structure 200
2second level filter structure 200 is located in the light path of first order filter structure 100 total reflection lights, incident light is through 100 light splitting of first order filter structure, the light of its total reflection part incides second level filter structure 200, be output filtering light through second level filter structure 200 transmissive portions, filtering bandwidth is λ
2-λ
1.; utilize the total reflection wave band of first order filter structure 100 and the transmission wave band of second level filter structure 2001 to be combined filtering; and by changing voltage V1 and V2, change the liquid crystal layer refractive index of first order filter structure 100 and second level filter structure 200, thereby regulate critical wavelength λ
1and λ
2, realize the tuber function of bandpass filter bandwidth width and bandwidth location.
Although specifically show and introduced the present invention in conjunction with preferred embodiment; but those skilled in the art should be understood that; not departing from the spirit and scope of the present invention that appended claims limits; the various variations of in the form and details the present invention being made, are protection scope of the present invention.
Claims (5)
1. an adjustable filter structure, comprises the first optical element and the second optical element, it is characterized in that: described the first optical element and the second optical element have two apparent surfaces that are parallel to each other, and are respectively first surface and second surface; Filling liquid crystal layer between first surface and second surface, arranges respectively transparency electrode between liquid crystal layer and two surfaces, between two transparency electrodes, applies variable voltage; The refractive index of the first optical element and the second optical element is all greater than the refractive index of liquid crystal layer; Incident light is in the interphase light splitting of first surface and liquid crystal layer, and the optical wavelength that the angle of total reflection equals incident angle is critical wavelength, and the light that wavelength is more than or equal to critical wavelength is totally reflected output, and wavelength is less than the light transmission output of critical wavelength; Described critical wavelength changes with the variation of the variable voltage applying between two transparency electrodes.
2. a kind of adjustable filter structure as claimed in claim 1, is characterized in that: the logical light face of described first surface, second surface, the first optical element and the second optical element is all coated with full wave anti-reflection film.
3. an adjustable filter, is characterized in that: comprise two filter structures as described in claim 1 or 2 any one, be respectively first order filter structure and second level filter structure, the critical wavelength of first order filter structure is λ
1, the critical wavelength of second level filter structure is λ
2, λ
1with λ
2unequal; Incident light passes through first order filter structure and second level filter structure successively, by second level filter structure output filtering light.
4. a kind of adjustable filter as claimed in claim 3, is characterized in that: the critical wavelength λ of described first order filter structure
1be greater than the critical wavelength λ of second level filter structure
2; Second level filter structure is located in the light path of first order filter structure transmitted light, and incident light is through first order filter structure, and the light of transmissive portion incides second level filter structure, and through the second level, filter structure total reflection part is output filtering light, and filtering bandwidth is λ
1-λ
2.
5. a kind of adjustable filter as claimed in claim 3, is characterized in that: the critical wavelength λ of described first order filter structure
1be less than the critical wavelength λ of second level filter structure
2; Second level filter structure is located in the light path of first order filter structure total reflection light, and incident light is through first order filter structure, and the light of total reflection part incides second level filter structure, is output filtering light through second level filter structure transmissive portion, and filtering bandwidth is λ
2-λ
1.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201210549782.5A CN103869510A (en) | 2012-12-18 | 2012-12-18 | Tunable filtering structure and filter |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201210549782.5A CN103869510A (en) | 2012-12-18 | 2012-12-18 | Tunable filtering structure and filter |
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| CN103869510A true CN103869510A (en) | 2014-06-18 |
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| CN201210549782.5A Pending CN103869510A (en) | 2012-12-18 | 2012-12-18 | Tunable filtering structure and filter |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108710200A (en) * | 2018-06-29 | 2018-10-26 | 昂纳信息技术（深圳）有限公司 | A kind of optical filter of flat-head type |
| CN109445024A (en) * | 2018-12-22 | 2019-03-08 | 复旦大学 | A kind of optical band pass filter of flat-top banding pattern |
| CN109445155A (en) * | 2018-12-22 | 2019-03-08 | 复旦大学 | A kind of unpolarized type narrow-band optical bandpass filter of electric tuning |
Citations (4)
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|---|---|---|---|---|
| US4840461A (en) * | 1986-10-07 | 1989-06-20 | British Telecommunications Public Limited Company | Optical switching devices having liquid crystal with splayed molecular orientation |
| US5377026A (en) * | 1992-09-02 | 1994-12-27 | Liu; Jian-Yu | Modulator using the linear electro-optic effect of liquid crystals |
| CN1599877A (en) * | 2001-12-06 | 2005-03-23 | 西铁城时计株式会社 | Liquid crystal variable wavelength filter unit, and driving method thereof |
| CN1723402A (en) * | 2003-01-07 | 2006-01-18 | 周平 | Methods and apparatus for optical communication |
-
2012
- 2012-12-18 CN CN201210549782.5A patent/CN103869510A/en active Pending
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4840461A (en) * | 1986-10-07 | 1989-06-20 | British Telecommunications Public Limited Company | Optical switching devices having liquid crystal with splayed molecular orientation |
| US5377026A (en) * | 1992-09-02 | 1994-12-27 | Liu; Jian-Yu | Modulator using the linear electro-optic effect of liquid crystals |
| CN1599877A (en) * | 2001-12-06 | 2005-03-23 | 西铁城时计株式会社 | Liquid crystal variable wavelength filter unit, and driving method thereof |
| CN1723402A (en) * | 2003-01-07 | 2006-01-18 | 周平 | Methods and apparatus for optical communication |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108710200A (en) * | 2018-06-29 | 2018-10-26 | 昂纳信息技术（深圳）有限公司 | A kind of optical filter of flat-head type |
| CN109445024A (en) * | 2018-12-22 | 2019-03-08 | 复旦大学 | A kind of optical band pass filter of flat-top banding pattern |
| CN109445155A (en) * | 2018-12-22 | 2019-03-08 | 复旦大学 | A kind of unpolarized type narrow-band optical bandpass filter of electric tuning |
| CN109445155B (en) * | 2018-12-22 | 2021-07-23 | 复旦大学 | Electrically tuned non-polarized narrow-band optical band-pass filter |
| CN109445024B (en) * | 2018-12-22 | 2021-10-26 | 复旦大学 | Flat-top-band type optical band-pass filter |
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