CN102798987B - Tunable optical filter with fixed frequency space and single-mode output - Google Patents

Tunable optical filter with fixed frequency space and single-mode output Download PDF

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Publication number
CN102798987B
CN102798987B CN201210265873.6A CN201210265873A CN102798987B CN 102798987 B CN102798987 B CN 102798987B CN 201210265873 A CN201210265873 A CN 201210265873A CN 102798987 B CN102798987 B CN 102798987B
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optical
fabry
catoptron
perot
glass sheet
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CN102798987A (en
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高培良
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Optoelectronic Technology Co Ltd Tianjin Odd Spectrum
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Optoelectronic Technology Co Ltd Tianjin Odd Spectrum
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Priority to PCT/CN2013/076163 priority patent/WO2014019399A1/en
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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 
    • G02F1/21—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  by interference
    • 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 
    • G02F1/21—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  by interference
    • G02F1/213—Fabry-Perot type
    • 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
    • G02F2203/00—Function characteristic
    • G02F2203/07—Polarisation dependent

Abstract

The invention relates to a tunable optical filter with fixed frequency space and single-mode output. The main technical characteristics of the tunable optical filter are as follows: the optical filter comprises a Fabry-Perot etalon and a transmission frequency tunable Fabry-Perot filter; the Fabry-Perot etalon and the transmission frequency tunable Fabry-Perot filter have the same response rang, and the transmission frequency tunable Fabry-Perot filter is only effective on linearly polarized lights in the specific polarization direction. The optical filter is reasonable to design, and free from mechanical movement component, has the characteristics of stable and reliable performance, simple structure, low cost, small size, simplicity of installation and production and so on, can reliably run under the extreme working environment with small size requirement, and can be widely applied to fields such as laser, optical test, optical fiber communication, biology, medical instrument and optical fiber sensor network.

Description

The tunable optical filter of a kind of fixed frequency interval and single-mode output
Technical field
The invention belongs to photoelectric field, the tunable optical filter of especially a kind of fixed frequency interval and single-mode output.
Background technology
Traditional optical method F-P etalon is a kind of filtering device utilizing multiple-beam interference principle to make, and mainly contains two kinds: a kind of is airspace, and another kind is optical glass interval.By the multiple-beam interference effect of the high reflectance institute forming method Fabry-Perot-type cavity of multilayer dielectric film on two logical light faces, the multi-wavelength narrow-band filtering that can be implemented in broad spectrum exports, the characteristic such as there is stable performance, clear aperature is large, luminous power damage threshold is high, structure is simple and cost is low, therefore, be widely used in all kinds of laser instrument, optical gauge and photoconductive fiber communication apparatus.Utilize traditional optical method F-P etalon also can realize the tuning of transmitted light frequency.For the Fabry-Perot etalon of airspace, incident angle by changing light carries out tuning, but the tuning range of this method is very little, or mechanically (as step motor) changes that the chamber of Fabry-Perot etalon is long to be realized, this method can realize large tuning range, but tuning precision is low, and high to the accuracy requirement of mechanical part, and stability is bad.Along with the development of PZT piezoelectric ceramics (lead zirconate titanate) technology, high-precision displacement can be realized.Adopt this technology long to the chamber changing Fabry-Perot etalon, tuning precision and speed can be improved, but not easily accomplish miniaturization, and drive source is also more complicated.Although tuning by what change that the temperature of etalon also can realize in a big way, the shortcoming of this method is that speed is slow.
Multi-frequency or the multimode output of the output of simplex method F-P etalon or simplex method Fabry-Perot filters to be a kind of gap periods be its Free Spectral Range, such as, Free Spectral Range is 100GHz, then within the scope of 1000GHz, just can there be 10 the arrowband multimode outputs being spaced apart 100GHz.Only have when frequency range is less than Free Spectral Range, single-frequency could be realized and export.If increase Free Spectral Range, the thickness of Fabry-Perot etalon will be reduced, such as, to the light wave of 1500 nanometers, according to common melting quartz glass, the thickness that the Free Spectral Range of 100GHz and 1000GHz is corresponding is about 1 millimeter and 0.1 millimeter respectively, therefore, even if accomplish the Free Spectral Range of 1000GHz, be actually very difficult, say nothing of larger Free Spectral Range.In sum, in actual applications, be in the wide scope of tens nanometers at a spectrum, adopting simplex method Fabry-Perot filters to go to realize, single mode tuning exports is almost impossible.
Summary of the invention
The object of the invention is to overcome the deficiencies in the prior art, the tunable optical filter of a kind of fixed frequency interval and single-mode output is provided, it differs certain intervals by the Free Spectral Range of Fabry-Perot etalon with the intrinsic Free Spectral Range of described tunable fabry-perot filter, and utilize the tunable feature of described tunable fabry-perot filter frequencies of transmission, in certain spectral range, realize the tunable single mode output function identical with the Free Spectral Range of Fabry-Perot etalon.
The present invention solves existing technical matters and takes following technical scheme to realize:
The tunable optical filter of a kind of fixed frequency interval and single-mode output, the Fabry-Perot etalon be oppositely arranged by front and back and a frequencies of transmission tunable fabry-perot filter are formed, and this Fabry-Perot etalon has identical spectral response range with frequencies of transmission tunable fabry-perot filter and frequencies of transmission tunable fabry-perot filter is only effective to the linearly polarized light with particular polarization.
And described Fabry-Perot etalon has certain Free Spectral Range and acutance coefficient; The intrinsic Free Spectral Range of described frequencies of transmission tunable fabry-perot filter when non-added electric field is less than the Free Spectral Range of Fabry-Perot etalon, and its difference is greater than the acutance coefficient of Fabry-Perot etalon or is greater than the acutance coefficient of described frequencies of transmission tunable fabry-perot filter.
And, described frequencies of transmission tunable fabry-perot filter comprises the first catoptron, liquid crystal material, the second catoptron and driving circuit, the logical light face arranged outside high reflectance multilayer dielectric film of described first catoptron, inside the logical light face of the first catoptron, ground floor arranges optical anti-reflective film, and this optical anti-reflective film arranges transparency electrode; The arranged outside high reflectance multilayer dielectric film of described second catoptron, the inner side ground floor of the second catoptron arranges optical anti-reflective film, this optical anti-reflective film arranges transparency electrode, in this transparency electrode, thickness setting is the non-conducting material film of several microns to tens microns, cover part except clear aperature except and a wide passage towards mirror edge of a millimeter and with first catoptron inside form the cavity that a thickness is several microns to tens microns, described liquid crystal material is placed in this cavity; Described driving circuit is connected in two transparency electrodes, keeping parallelism and mechanics Fabry-Perot-type multiple-beam interference chamber outside the logical light face of the first catoptron and outside the logical light face of the second catoptron.
And, described frequencies of transmission tunable fabry-perot filter comprises the first catoptron, liquid crystal material, the second catoptron and driving circuit, the logical light face arranged outside optical anti-reflective film of described first catoptron, inside the logical light face of the first catoptron, ground floor arranges high reflectance multilayer dielectric film, and this high reflectance multilayer dielectric film arranges transparency electrode; The arranged outside high reflectance multilayer dielectric film of described second catoptron, the inner side ground floor of the second catoptron arranges optical anti-reflective film, this optical anti-reflective film arranges transparency electrode, in this transparency electrode, thickness setting is the non-conducting material film of several microns to tens microns, cover part except clear aperature except and a wide passage towards mirror edge of a millimeter and with first catoptron inside form the cavity that a thickness is several microns to tens microns, described liquid crystal material is placed in this cavity; Described driving circuit is connected in two transparency electrodes, keeping parallelism and mechanics Fabry-Perot-type multiple-beam interference chamber inside the logical light face of the first catoptron and outside the logical light face of the second catoptron.
And, described frequencies of transmission tunable fabry-perot filter comprises the first catoptron, liquid crystal material, the second catoptron and driving circuit, the logical light face arranged outside optical anti-reflective film of described first catoptron, inside the logical light face of the first catoptron, ground floor arranges high reflectance multilayer dielectric film, and this high reflectance multilayer dielectric film arranges transparency electrode; The arranged outside optical anti-reflective film of described second catoptron, the inner side ground floor of the second catoptron arranges high reflectance multilayer dielectric film, this high reflectance multilayer dielectric film arranges transparency electrode, in this transparency electrode, thickness setting is the non-conducting material film of several microns to tens microns, cover part except clear aperature except and a wide passage towards mirror edge of a millimeter and with first catoptron inside form the cavity that a thickness is several microns to tens microns, described liquid crystal material is placed in this cavity; Described driving circuit is connected in two transparency electrodes, keeping parallelism and mechanics Fabry-Perot-type multiple-beam interference chamber inside the logical light face of the first catoptron and inside the logical light face of the second catoptron.
And described frequencies of transmission tunable fabry-perot filter comprises the first catoptron, the first optical clear glass sheet, liquid crystal material, the second optical clear glass sheet and the second catoptron, the logical light face arranged outside high reflectance multilayer dielectric film of described first catoptron is optical polish face inside the logical light face of the first catoptron, first optical clear glass sheet is arranged on inside the first catoptron, be optical polish face outside the logical light face of the first optical clear glass sheet, inside the logical light face of the first optical clear glass sheet, ground floor arranges optical anti-reflective film, and this optical anti-reflective film arranges transparency electrode, the logical light face arranged outside high reflectance multilayer dielectric film of described second catoptron is optical polish face inside the logical light face of the second catoptron, second optical clear glass sheet is arranged on inside the second catoptron, be optical polish face outside the logical light face of the second optical clear glass sheet, the inner side ground floor of the second optical clear glass sheet arranges optical anti-reflective film, this optical anti-reflective film arranges transparency electrode, in this transparency electrode, thickness setting is the non-conducting material film of several microns to tens microns, cover part except clear aperature except and a wide passage towards mirror edge of a millimeter and with first optical glass sheet inside form the cavity that a thickness is several microns to tens microns, described liquid crystal material is placed in this cavity, driving circuit is connected in the transparency electrode of the first optical clear glass sheet and the second optical clear glass sheet, keeping parallelism and mechanics Fabry-Perot-type multiple-beam interference chamber outside the logical light face of the first catoptron and outside the logical light face of the second catoptron.
And described frequencies of transmission tunable fabry-perot filter comprises the first catoptron, the first optical clear glass sheet, liquid crystal material, the second optical clear glass sheet and the second catoptron, the logical light face arranged outside optical anti-reflective film of described first catoptron, arranges high reflectance multilayer dielectric film inside the logical light face of the first catoptron, first optical clear glass sheet is arranged on inside the first catoptron, it is optical polish face or optical anti-reflective film is set outside the logical light face of the first optical clear glass sheet, inside the logical light face of the first optical clear glass sheet, ground floor arranges optical anti-reflective film, and this optical anti-reflective film arranges transparency electrode, the logical light face arranged outside high reflectance multilayer dielectric film of described second catoptron is optical polish face inside the logical light face of the second catoptron, second optical clear glass sheet is arranged on inside the second catoptron, be optical polish face outside the logical light face of the second optical clear glass sheet, the inner side ground floor of the second optical clear glass sheet arranges optical anti-reflective film, this optical anti-reflective film arranges transparency electrode, in this transparency electrode, thickness setting is the non-conducting material film of several microns to tens microns, cover part except clear aperature except and a wide passage towards mirror edge of a millimeter and with first optical glass sheet inside form the cavity that a thickness is several microns to tens microns, liquid crystal material is placed in this cavity, driving circuit is connected in the transparency electrode of the first optical clear glass sheet and the second optical clear glass sheet, keeping parallelism and mechanics Fabry-Perot-type multiple-beam interference chamber inside the logical light face of the first catoptron and outside the logical light face of the second catoptron.
And described frequencies of transmission tunable fabry-perot filter comprises the first catoptron, the first optical clear glass sheet, liquid crystal material, the second optical clear glass sheet and the second catoptron, the logical light face arranged outside optical anti-reflective film of described first catoptron, arranges high reflectance multilayer dielectric film inside the logical light face of the first catoptron, first optical clear glass sheet is arranged on inside the first catoptron, it is optical polish face or optical anti-reflective film is set outside the logical light face of the first optical clear glass sheet, inside the logical light face of the first optical clear glass sheet, ground floor arranges optical anti-reflective film, and this optical anti-reflective film arranges transparency electrode, the logical light face arranged outside optical anti-reflective film of described second catoptron, inside the logical light face of the second catoptron, ground floor arranges high reflectance multilayer dielectric film, second optical clear glass sheet is arranged on inside the second catoptron, it is optical polish face or optical anti-reflective film is set outside the logical light face of the second optical clear glass sheet, the inner side ground floor of the second optical clear glass sheet arranges optical anti-reflective film, this optical anti-reflective film arranges transparency electrode, in this transparency electrode, thickness setting is the non-conducting material film of several microns to tens microns, cover part except clear aperature except and a wide passage towards mirror edge of a millimeter and with first optical glass sheet inside form the cavity that a thickness is several microns to tens microns, described liquid crystal material is placed in this cavity, described driving circuit is connected in the transparency electrode of the first optical clear glass sheet and the second optical clear glass sheet, keeping parallelism and mechanics Fabry-Perot-type multiple-beam interference chamber inside the logical light face of the first catoptron and inside the logical light face of the second catoptron.
And what described liquid crystal material adopted is nematic phase type liquid crystal, and the thickness of this liquid crystal layer is several microns to tens microns.
And the first described catoptron and the second catoptron are optically transparent material and have identical optical index.
And described driving circuit is a kind of frequency is the square-wave pulse circuit of 1 KHz to 10 KHz, and pulse voltage amplitude is adjustable to 5 volts from 0 volt.
And the inner side of described first catoptron is mated with the outside optics transparent refractive rate of the first optical clear glass sheet and is gluingly connected together or adopts assemble method glue-free in industrial conventional logical light light path: the junction namely beyond logical light light path sticks with glue and connects; The inner side of described second catoptron is mated with the outside optics transparent refractive rate of the second optical clear glass sheet and is gluingly connected together or adopts assemble method glue-free in industrial conventional logical light light path: the junction namely beyond logical light light path sticks with glue and connects; The first described catoptron, the second catoptron, the first optical clear glass sheet and the second optical clear glass sheet are optically transparent material and have identical or substantially identical optical index; The refractive index of described optical clear index matching glue is substantially identical with optically transparent material refractive index.
And incident light enters described frequencies of transmission tunable fabry-perot filter from the logical light face of described Fabry-Perot etalon.
And incident light is from the tunable Fabry of described frequencies of transmission--perot filter leads to light face and enters described Fabry-Perot etalon.
Advantage of the present invention and good effect are:
The present invention is reasonable in design, a Fabry-Perot etalon and frequencies of transmission tunable fabry-perot (Fabry-Perot) wave filter combine by effectively, utilize the electro-optic birefringent effect of liquid crystal and optical phase modulation is produced to the linearly polarized light of a certain particular polarization of incidence in chamber liquid crystal being placed on Fabry-Perot etalon, realization is continuous to the frequency of the linearly polarized light of penetrant method Fabry-Perot filters, quick and fine tune.Because the thickness of liquid crystal layer is very thin, therefore can manufactured size is little, Free Spectral Range is large wideband adjustable fabry-perot filter, meanwhile, the fast precise that can be implemented in the light frequency in broad spectrum is tuning.The present invention has mechanical moving-member, stable and reliable for performance, structure is simple, cost is low, size is little, be easy to the features such as installation and production, the reliability service for requiring under the little and extreme operating environments of size can being met, having a wide range of applications in the other fields such as laser instrument, optic test, optical-fibre communications, biology, medicine equipment and Fibre Optical Sensor network.
Accompanying drawing explanation
Fig. 1 is the schematic diagram of common law F-P etalon;
Fig. 2 is a kind of structural representation comprising the tunable fabry-perot filter of nematic phase type liquid crystal material layer;
Fig. 3 is the change curve schematic diagram of phase place with extra electric field of light transmission liquid crystal material;
Fig. 4 is the schematic diagram comprising the tunable fabry-perot filter of nematic phase type liquid crystal material layer of another kind of structure;
Fig. 5 is the schematic diagram of Fabry-Perot etalon transmitted spectrum;
Fig. 6 is the schematic diagram of tunable fabry-perot filter transmitted spectrum;
Fig. 7 is structural representation of the present invention;
Fig. 8 is intrinsic transmitted spectrum schematic diagram of the present invention;
Fig. 9 is the tunable transmitted spectrum schematic diagram of fixed intervals of the present invention and single-mode output.
Embodiment
Below in conjunction with accompanying drawing, the embodiment of the present invention is further described.
Fig. 1 is a kind of schematic diagram of common Fabry-Perot (Fabry-Perot) light standard tool 100.The material of this Fabry-Perot light standard tool 100 generally adopts to resemble near infrared and visible light wave range and melts quartz or the such optical glass of BK7, suppose that the refractive index of material is n, highly reflecting films are all plated in two logical light faces 2 and 4, suppose that reflectivity is R, thickness is h, light is with the incident angles close to zero degree, then the Free Spectral Range FSR of light standard tool 100 can be expressed as: Δ λ=λ 2/ (2nh), or with frequency representation: Δ ν=c/ (2nh), wherein c is the light velocity.The crest frequency of transmitted light can be expressed as: ν=mc/ (2nh), and wherein m is order of interference, and the frequency broadband of transmitted light can be expressed as: Δ ν 1/2(FWHM)=c (1-R)/(2nhR 1/2), wherein c is the light velocity.
As can be seen from above-mentioned two formula, the Free Spectral Range FSR of light standard tool 100 and thickness are that h is inversely proportional to.Suppose that the refractive index of material is n=1.5, FSR be realized 1=100GHz, thickness h ≈ 1 millimeter.Require that FSR is larger, thickness is less.After the material of etalon and thickness are determined, the frequency broadband of transmitted light is main relevant with reflectivity R, and reflectivity is higher, frequency broadband or acutance (finesse) less.The feature of the transmitted spectrum of Fabry-Perot (Fabry-Perot) etalon is that the bandwidth of each transmission spectrum can be accomplished very narrow, and the equal and non-constant width of light bands width of the frequency interval of transmitted spectrum, generally can cover the optical spectral of more than 100 nanometers.Fig. 5 gives the schematic diagram of Fabry-Perot light standard tool 100 output spectrum.
Fig. 2 gives a kind of tunable fabry-perot filter utilizing nematic phase type liquid crystal the refractive index of linearly polarized light to be produced to change and design under electric field action.The general liquid crystal material being used as photoelectric device has high resistivity.Therefore, desirable dielectric substance can be considered to.Owing to forming the orderly orientation of molecule and the form of extension elongation, liquid crystal has anisotropic dielectric characteristic and mono-symmetry, and as a uniaxial crystal, the direction of its optical axis is consistent with the oriented of molecule.When under the effect of liquid crystal molecule at external electrical field, electric dipole can be formed.Under the moment loading that electric dipole is formed, making the orientation of liquid crystal molecule turn to the direction of electric field, by changing the power of electric field, the direction of the optical axis of liquid crystal can be changed.Therefore, can utilize this characteristic of liquid crystal, make optical phase modulator, tunable optic filter, or other photoelectric devices, as photoswitch and light intensity modulator etc.The general thickness being used as the liquid crystal coatings of photoelectric device is several microns to tens microns.
As shown in Figure 2, a kind of tunable fabry-perot filter 200 comprises the first catoptron 10, liquid crystal material 18, second catoptron 20 and driving circuit 14, first catoptron 10 and the second catoptron 20 is optically transparent material.
Tunable fabry-perot filter 200 has three kinds of different structures, illustrates respectively below:
The first structure of tunable fabry-perot filter 200 is: on the logical light face outer surface 8 and 22 of the first catoptron 10 and the second catoptron 20, be coated with high reflectance multilayer dielectric film, forming method Fabry-Perot-type (Fabry-Perot) chamber between two high reflectance multilayer dielectric films respectively; Optical anti-reflective film 12 and transparency electrode rete 16 is provided with from inside to outside successively inside the logical light face of the first catoptron 10; Inside the logical light face of the second catoptron 20, be provided with optical anti-reflective film 24, transparency electrode 26 and non-conducting material film 19 from inside to outside successively, optical anti-reflective film 12 and optical anti-reflective film 24 are plated in the logical light face inside surface of the first catoptron 10 and the logical light face inside surface at the second catoptron 20 respectively.The thickness of non-conducting material film 19 is several microns to tens microns, and cover other parts except clear aperature and a wide passage leading to mirror edge of a millimeter, object provides an exit passageway for being infused in liquid crystal unnecessary in chamber.It is that the cavity in tens microns, several microns of roads is for arranging liquid crystal material 18 that this non-conducting material film 19 forms a thickness with the inner side of described first catoptron 10, what this liquid crystal material 18 adopted is nematic phase type liquid crystal, and the thickness of this liquid crystal material is about several microns to tens microns.Due to the thickness of liquid crystal very little (several microns to tens microns), therefore, the tunable fabry-perot filter of intrinsic Free Spectral Range (namely at the Free Spectral Range without tunable optic filter during extra electric field) can be made.Two transparency electrodes are connected with driving circuit 14, and the drive singal produced by driving circuit is formed and drives electric field between two transparency electrode retes; Utilize electric field to change the effective refractive index n of Fabry-Perot intraluminal fluid crystalline substance, regulate light frequency ν and the Free Spectral Range (FSR) of the transmitted light of fabry-perot filter.Common driving electric field is voltage is a few volt, and frequency is the square-wave signal of 1 KHz to a few KHz.
In such as Fig. 2, the light beam 6 inciding wave filter 200 a branch ofly to propagate in the z-direction, and polarization axle is the linearly polarized light in x direction, suppose that the refractive index of light transparent materials is n, highly reflecting films are all plated in two logical light faces 8 and 22, suppose that reflectivity is R, thickness is D, then the Free Spectral Range FSR of wave filter 200 1be respectively with transmitted light frequency: Δ λ=λ 2/ (2nD+ Γ), or with frequency representation: Δ ν=c/ (2nD+ Γ), wherein c is the light velocity, and Γ representative is changed the light path produced incident light under DC Electric Field by refraction by liquid crystal.The crest frequency of transmitted light can be expressed as: ν=mc/ (2nD+ Γ), and wherein m is order of interference, and the frequency broadband (also claiming acutance coefficient) of transmitted light can be expressed as: Δ ν 1/2(FWHM)=c (1-R)/((2nD+ Γ) R 1/2), wherein c is the light velocity.
Fig. 3 give a thickness be the nematic phase type liquid crystal of 10 microns under the driving of 2KHz square-wave voltage, to optical wavelength be 1550 nanometers phase of light wave change relation.The maximum light phase realizing about 2 π postpones.According to above-mentioned formula, tunable fabry-perot filter 200 can obtain the tuning range of the transmitted light frequency of about 100GHz for the linearly polarized light close to zero degree incidence.Comparatively speaking, according to formula above, to the bandwidth Δ ν of Free Spectral Range Δ ν and transmitted light 1/2change be much smaller.Fig. 6 is the transmitted spectrum schematic diagram of tunable fabry-perot filter 200.
As can be seen here, tunable fabry-perot filter 200, under the effect of extra electric field, can realize the tuning of transmitted light frequency in a big way and substantially not change frequency broadband and the Free Spectral Range of transmitted light.This characteristic is for by many for tunable fabry-perot filter 200 application, as significant in laser instrument and frequency spectrum instrument etc.
The second structure of tunable fabry-perot filter 200 is: lead to light face outer surface 8 at the first catoptron 10 and plate optical anti-reflective film; Inside the logical light face of the first catoptron 10, be provided with high reflectance multilayer dielectric film 12 and transparency electrode rete 16 from inside to outside successively, other structures are identical with the first structure of tunable fabry-perot filter 200.The feature of the second structure of tunable fabry-perot filter 200 to realize the Free Spectral Range larger than the first structure.
The third structure of tunable fabry-perot filter 200 is: outside the logical light face of the second catoptron 20, plate optical anti-reflective film; High reflectance multilayer dielectric film 24, transparency electrode 26 and non-conducting material film 19 is provided with from inside to outside successively inside the logical light face of the second catoptron 20.Other structures are identical with the second structure of tunable fabry-perot filter 200.The feature of the third structure of tunable fabry-perot filter 200 to realize the Free Spectral Range larger than the second structure.
Because tunable fabry-perot filter 200 is when making, require the surperficial perfect parallelism in the logical light face of two catoptrons plating high reflectance multilayer dielectric films, this assembling for tuning method Fabry-Perot filters 200 brings certain difficulty.For this reason, we devise another tunable fabry-perot filter 300, as shown in Figure 4.Tunable fabry-perot filter 300 comprises the first catoptron 32, first optical glass sheet 36, liquid crystal material 41, second optical glass sheet 50, second catoptron 46 and driving circuit 56.The difference of wave filter 300 and wave filter 200 is, in wave filter 300, first liquid crystal material 41 is positioned between two optical clear glass sheet 36 and 50, antireflection layer 38 and 52 is coated with respectively inside the logical light face of above-mentioned two optical clear glass sheet 36 and 50, transparency electrode 40 and 54, and the inner side of the thin layer 41 and first optical clear glass sheet 36 that arrange one deck non-conducting material on optical clear glass sheet 50 forms a thickness is that the cavity in tens microns, several microns of roads is for placing liquid crystal material.Another logical light face not plated film or plating optical anti-reflective film of above-mentioned two optical clear glass sheet 36 and 50, optical clear glass sheet 36 and 50 and liquid crystal material 42 form a liquid crystal cell.When assembling above-mentioned liquid crystal cell, not needing the logical light face of optical clear glass sheet 36 and 50 to keep perfect parallelism, like this, being easier to operation at assembling time ratio.
Tunable fabry-perot filter 300 also has three kinds of different structures, illustrates respectively below:
The first structure of tunable fabry-perot filter 300 is: the outside of the first catoptron 32 leads to light face 30 and is coated with high reflection film, and it is the polished surface not having plated film that inner side leads to light face.First the outside index matching glue 34 of the optical clear glass sheet 36 on the inner side of the first catoptron 32 and above-mentioned liquid crystal cell is bonded together.The outside of the second catoptron 46 leads to light face 44 and is coated with high reflection film, and it is the polished surface not having plated film that inner side leads to light face.Then the inner side of the second catoptron 46 is led to light face index matching glue 48 to be bonded together with the outside of the optical clear glass sheet 50 on above-mentioned liquid crystal cell, in this process, the face 30 and 44 of two of two catoptrons 32 and 46 plating high reflection films is just needed to adjust perfect parallelism, to realize the effect of the multiple-beam interference of Fabry-Perot etalon.Under normal circumstances, because 32,36,50 and 46 optically transparent materials adopted have identical or close to identical light refractive index, index matching glue 48 and index matching glue 34 are also identical or close to identical.Owing to have employed four pieces of optically transparent materials, therefore the shortcoming of this structure of wave filter 300 is that its Thickness Ratio wave filter 200 wants large.According to calculating above, to light and the common optical glass material (refractive index is about 1.5) of 1550 nanometers, when Free Spectral Range is 100GHz, thickness H is approximately 1 millimeter, if need larger Free Spectral Range, compares and is difficult to realize.
The second structure of tunable fabry-perot filter 300 is: the outside of the first catoptron 32 leads to light face 30 and plates optical anti-reflective film, and inner side leads to light face plating high reflection film.Optical anti-reflective film can be plated in the outside of the optical clear glass sheet 36 on above-mentioned liquid crystal cell, also can not the polished surface of plated film.Be bonded together with index matching glue 34 outside optical clear glass sheet 36 on the inner side of the first catoptron 32 and above-mentioned liquid crystal cell, also can adopt assemble method glue-free in industrial conventional light path, namely only two optical element places led to beyond light light path be sticked with glue and connect.Other structures are identical with the first structure of wave filter 300.Because Fabry-Perot-type cavity is that the high reflection film that the outside leading to light face and the second catoptron 46 by the inner side of the first catoptron 32 leads on light face is formed, therefore, the feature of this structure is the Free Spectral Range that can realize more strengthening than the first structure of wave filter 300.
The third structure of tunable fabry-perot filter 300 is: the difference of the second structure of this structure and wave filter 300 is: the outside of the second catoptron 46 leads to light face 44 and plates optical anti-reflective film, and inner side leads to light face plating high reflection film.The outside of the optical clear glass sheet 50 on above-mentioned liquid crystal cell leads to light face and can plate optical anti-reflective film film, also can be the polished surface of not plated film.The second reflection inner side of 46 is together with the outside index matching glue bond of the optical clear glass sheet 50 on above-mentioned liquid crystal cell, also can adopt assemble method glue-free in industrial conventional light path, namely only two optical element places led to beyond light light path be sticked with glue and connect.Other structures are identical with the second structure of wave filter 300.Because Fabry-Perot-type cavity is that the high reflection film that the inner side leading to light face and the second catoptron 46 by the inner side of the first catoptron 32 leads on light face is formed, therefore, the feature of this structure to realize the Free Spectral Range larger than the second structure of wave filter 300.
Below in conjunction with Fig. 7, the present invention will be described.
The tunable optical filter 400 of a kind of fixed frequency interval and single-mode output is made up of Fabry-Perot etalon 100 and tunable fabry-perot filter 200 or 300.The Free Spectral Range of Fabry-Perot etalon 100 is FSR 1, the Free Spectral Range of tunable fabry-perot filter 200 or 300 is FSR 2, FSR 2compare FSR 1little Δ f, as shown in Figure 5 and Figure 6.If Δ f=0.25FSR 1, then in the spectral range of ν 1 to ν 4, penetrant method F-P etalon 100 has 4 moulds, and has 5 moulds through tunable fabry-perot filter 200 or 300.Therefore, only have ν 1 and ν 4 two moulds through tunable optic filter 400, in other words, tunable optic filter 400 is the FSR of 4 times 2or the FSR of 3 times 1, as shown in Figure 8.As seen in Figure 8, by regulating the value of Δ f, the Free Spectral Range FSR of tunable optic filter 400 can greatly be increased 3.
When practical application, the difference of FSR2 and FSR1 can be regulated as required, can FSR be regulated 3, but its lowest difference is apart from the Δ ν that should be equal to or greater than two times 1/2, to ensure the single-mode output characteristic of tunable optic filter 400.
Below tuning process of the present invention is described: with reference to figure 5 and Fig. 6, as the transmission spectrum ν of tunable fabry-perot filter 200 or 300 2abe tuned to the ν of Fabry-Perot etalon 100 2during coincidence, within the scope of spectrum FSR3, only has ν 2can through tunable optic filter 400.Similarly, as the transmission spectrum ν of tunable fabry-perot filter 200 or 300 3abe tuned to the ν of Fabry-Perot etalon 100 3during coincidence, within the scope of spectrum FSR3, only has ν 3can through tunable optic filter 400, as shown in Figure 8.But at tuning ν 3aprocess in, due to ν 2acan through ν 2, therefore, can through tunable optic filter 400, the method eliminating this phenomenon is in tuning process, increases a fast optical switch based at the output terminal of wave filter 400.When from a mould be tuned to another mould process in, photoswitch is closed, by the time ν 3aand ν 3after coincidence, then open photoswitch.Other moulds tuning, can the like.Because the maximum difference of Fabry-Perot etalon 100 and tunable fabry-perot filter 200 or 300 two adjacent transmissive spectrums is less than FSR1, therefore, as long as can ensure that the tunable range of the transmission spectrum of tunable fabry-perot filter 200 or 300 equals or close to FSR1, tunable optic filter 400 just can realize within the scope of spectrum FSR3, realize the tunable output of single mode at equal intervals that frequency interval is FSR1, and it is tunable transmitted spectrum as shown in Figure 9.It should be noted that, when incident light enters into described tunable optical filter 400 from the logical light face of tunable fabry-perot filter 200 or 300, also can realize the output at same single mode and fixed frequency interval, but in different applications, its output spectrum width may be different.
It is emphasized that above-mentioned explanation only plays demonstration and describes, be not one and exhaustively illustrate in detail, be not also intended to limit the present invention on described concrete form.Through description above, all may occur many changes of the present invention and change.Selected concrete enforcement is only used to the application better explained in principle of the present invention and reality.This explanation can make the people being familiar with this field better can utilize the present invention, designs different concrete enforcement according to actual needs and changes accordingly.

Claims (8)

1. the tunable optical filter of a fixed frequency interval and single-mode output, it is characterized in that: the Fabry-Perot etalon be oppositely arranged by front and back and a frequencies of transmission tunable fabry-perot filter are formed, this Fabry-Perot etalon has identical spectral response range with frequencies of transmission tunable fabry-perot filter and frequencies of transmission tunable fabry-perot filter is only effective to the linearly polarized light with particular polarization;
Described frequencies of transmission tunable fabry-perot filter comprises the first catoptron, the first optical clear glass sheet, liquid crystal material, the second optical clear glass sheet and the second catoptron, the logical light face arranged outside high reflectance multilayer dielectric film of described first catoptron is optical polish face inside the logical light face of the first catoptron, first optical clear glass sheet is arranged on inside the first catoptron, be optical polish face outside the logical light face of the first optical clear glass sheet, inside the logical light face of the first optical clear glass sheet, ground floor arranges optical anti-reflective film, and this optical anti-reflective film arranges transparency electrode, the logical light face arranged outside high reflectance multilayer dielectric film of described second catoptron is optical polish face inside the logical light face of the second catoptron, second optical clear glass sheet is arranged on inside the second catoptron, be optical polish face outside the logical light face of the second optical clear glass sheet, the inner side ground floor of the second optical clear glass sheet arranges optical anti-reflective film, this optical anti-reflective film arranges transparency electrode, in this transparency electrode, thickness setting is the non-conducting material film of several microns to tens microns, cover part except clear aperature except and a wide passage towards mirror edge of a millimeter and with first optical glass sheet inside form the cavity that a thickness is several microns to tens microns, described liquid crystal material is placed in this cavity, driving circuit is connected in the transparency electrode of the first optical clear glass sheet and the second optical clear glass sheet, keeping parallelism and mechanics Fabry-Perot-type multiple-beam interference chamber outside the logical light face of the first catoptron and outside the logical light face of the second catoptron.
2. the tunable optical filter of a kind of fixed frequency interval according to claim 1 and single-mode output, is characterized in that: described Fabry-Perot etalon has certain Free Spectral Range and acutance coefficient; The intrinsic Free Spectral Range of described frequencies of transmission tunable fabry-perot filter when non-added electric field is less than the Free Spectral Range of Fabry-Perot etalon, and its difference is greater than the acutance coefficient of Fabry-Perot etalon or is greater than the acutance coefficient of described frequencies of transmission tunable fabry-perot filter.
3. the tunable optical filter of a kind of fixed frequency interval according to claim 1 and single-mode output, is characterized in that: what described liquid crystal material adopted is nematic phase type liquid crystal, and the thickness of this liquid crystal material is several microns to tens microns.
4. the tunable optical filter of a kind of fixed frequency interval according to claim 1 and single-mode output, is characterized in that: the first described catoptron and the second catoptron are optically transparent material and have identical optical index.
5. the tunable optical filter of a kind of fixed frequency interval according to claim 1 and single-mode output, it is characterized in that: described driving circuit is a kind of frequency is the square-wave pulse circuit of 1 KHz to 10 KHz, and pulse voltage amplitude is adjustable to 5 volts from 0 volt.
6. the tunable optical filter of a kind of fixed frequency interval according to claim 1 and single-mode output, is characterized in that: the inner side of described first catoptron is mated with the outside optics transparent refractive rate of the first optical clear glass sheet and is gluingly connected together or adopts assemble method glue-free in industrial conventional logical light light path: the junction namely beyond logical light light path sticks with glue and connects; The inner side of described second catoptron is mated with the outside optics transparent refractive rate of the second optical clear glass sheet and is gluingly connected together or adopts assemble method glue-free in industrial conventional logical light light path: the junction namely beyond logical light light path sticks with glue and connects; The first described catoptron, the second catoptron, the first optical clear glass sheet and the second optical clear glass sheet are optically transparent material and have identical or substantially identical optical index; The refractive index of described optical clear index matching glue is substantially identical with optically transparent material refractive index.
7. the tunable optical filter of a kind of fixed frequency interval according to claim 1 and single-mode output, is characterized in that: incident light enters described frequencies of transmission tunable fabry-perot filter from the logical light face of described Fabry-Perot etalon.
8. the tunable optical filter of a kind of fixed frequency interval according to claim 1 and single-mode output, is characterized in that: incident light leads to light face from described frequencies of transmission tunable fabry-perot filter and enters described Fabry-Perot etalon.
CN201210265873.6A 2012-07-30 2012-07-30 Tunable optical filter with fixed frequency space and single-mode output Expired - Fee Related CN102798987B (en)

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