CN101414027B - Two- and multi-exposure sampling Bragg grating and making method thereof - Google Patents

Abstract

The invention discloses a double- or multiple-exposure sampled Bragg grating, wherein, the sampled Bragg grating which is formed by double holographic exposure and based on reconstruction-equivalent chirp technology is divided into two parts with equal length in a sampling interval and is written into two Bragg gratings with different phases. When the phase difference between the Bragg gratings included by the two parts is pi, zero-level shadow grating and all other even-level shadow gratings disappear, plus or minus 1 level intensity reaches the maximum value which is 64% of the grating of an even DFB structure and is twice of the plus or minus 1 level intensity of a single-exposure sampled grating. Each sample of the sampled Bragg grating is divided into m parts with equal distance, the phase of the n-th part in each sample is n multiplied by (2pi/m), and the 1 level shadow grating of the sampled grating has the maximum effective intensity which is the m/pi multiplied by sin(pi/m) multiplied by 100 of an even Bragg grating; or the phase of the n-th part in each sample is -n multiplied by (2pi/m), the -1 level shadow grating of the sampled grating has the maximum effective intensity which is the m/pi multiplied by sin(pi/m) multiplied by 100 of the even Bragg grating.

Description

Twice and multi-exposure sampling Bragg grating and method for making

One, technical field

The invention belongs to the photoelectron technology field, relate to optical communication, aspects such as Fibre Optical Sensor.Relevant with distributed feedback semiconductor laser, distributed feedback semiconductor passive device, distributed feedback optical fiber laser, distributed feed-back fiber optic passive device etc., the design and fabrication that relates to the complex distributions feedback device, be widely used in all kinds of optical waveguides, be widely used in all kinds of sampling structures.More specifically, be based on design and the making that reconstruct-equivalent chirp technology prepares distributed feed-back (DFB) device.

Two, background technology

21st century is the century of infotech.Optical communication is along with the development of infotech is advanced by leaps and bounds, maked rapid progress.When optical communication technique was maked rapid progress, the challenge that optic communication device ran into was also more and more.How to satisfy the requirement of market, manufacture out low-cost and high performance optical communication product, become the topic that current optical communication industry is paid close attention to the most optic communication device.

In all kinds of optic communication devices, Prague (Bragg) grating is used very extensive, such as fiber laser, semiconductor laser, dispersion compensation multi-channel filter, Fibre Optical Sensor, optical code division multiple access (OCDMA) codec or the like.Yet,, very most advanced and sophisticated and nanoscale manufacturing technology costliness is indispensable if will in Bragg grating, realize accurate performance design, complicated filtering characteristic, phase shift accurately and warble etc.The research and development of optic communication device, its basic goal is industrialization, for the development of telecommunications is done one's bit, and its manufacture difficulty and too high cost are the greatest problem that industrialization runs into.Especially the optic communication device of based semiconductor material, as semiconductor laser array, manufacturing technology is the place of the root that it at present can't volume production.

Holographic exposure technology (holographic lithography) can form the DFB optical grating construction, is the effective means of making the low cost DFB device.But the Bragg grating of the index-coupled DFB device of making based on traditional holographic exposure technology is simple relatively evenly (uniform) structure, that is, the Bragg grating that comprises in the device has the identical grating cycle.The holographic exposure technical costs is extremely low, and is suitable for producing in batches.But the passive device that the holographic exposure technology is made only has simple filter function; The active device of making (laser instrument) is dual-mode of operation in theory.In actual applications because laser instrument both sides end face reflected phase will difference can realize single module lasing.But its reflected phase will has randomness, and its single mode yield rate is not high; And during High Speed Modulation, its side mode suppression ratio (SMSR) can't satisfy the needs of high speed optical communication fully less than 20dB.

Electron beam lithography (electron beam lithography) can form very complicated DFB optical grating construction, it is extremely successful often to be used to make complicated microstructure in scientific research, and can be used for developing very complicated high-performance, high finished product rate Distributed Feedback Laser, comprise the chip of laser of dwdm system application etc.But the disposable input of the equipment of electron beam lithography is very big, the operating cost height, and big when chip structure variation, fine structure difference, when structural change density is very high, need meticulous inscription, cause be multiplied needed working time, make the cost of making baroque DWDM chip of laser higher, be difficult to adapt to the needs of following low cost, high performance chips exploitation, production.

For making the high performance device can volume production, reconstruct-equivalent chirp (Reconstruction-equivalent-chirp) technology (REC technology) be arisen at the historic moment.By carry out sampling (sample) modulation of globality on Bragg grating, reconstruct-equivalent chirp technology can be realized complicated architectural characteristic in sub-micron even micron precision; Reconstruct simultaneously-equivalent chirp technology uses the most common holographic exposure technology, makes the device with labyrinth possess the possibility of volume production.

Reconstruct-equivalent chirp technology carries out sample modulation by the uniform grating that holographic exposure is formed, and (in semiconductor devices, the sample modulation precision is a sub-micron; In optical fibre device, the sample modulation precision is a submillimeter), realized multiple high-performance optical fiber device, also succeed at the semiconductor planar waveguide device, wherein most typical is optical code division multiple access (OCDMA) encoding and decoding sheets, has broken by the Japanese OKI the highest OCDMA encoding and decoding sheet that company/Japanese national communication research institute/Osaka university keeps and has counted world record.Reconstruct-equivalent chirp technology and equivalent chirp technology are closely related, and the characteristics of this equivalent chirp technology are to adopt sub-micrometer precision just can make the Bragg grating with required equivalent chirp.This special Bragg grating is a sampling Bragg grating.Sampling Bragg grating has a plurality of reflection peaks, and each reflection peak is represented a shadow grating (ghost grating), corresponding fourier coefficient.The shadow grating of representing fourier coefficient+1 and-1 respectively at two reflection peaks of the left side of centre wavelength (the wavelength of weak point) and the right (long wavelength) respectively that the decentering bragg wavelength is nearest, its effect is identical with common even (uniform) Bragg grating (non-sampling Bragg grating).Therefore with the distribution in complicated sampling period form complexity+1 or-1 grade shadow grating, can replace common Bragg grating, be called equivalent grating.The equivalence grating can replace common Bragg grating and realize identical performance.Its complex characteristics can distribute by the sampling period that changes sampling grating and obtain.Sampling period generally will be far longer than the grating cycle, therefore can simplify its production process greatly.The method has very big cost advantage and technical characteristic, and can design the equivalent grating with different optical response, and need not to change its Bragg grating cycle.The equivalence grating also can be in order to equivalent chirp and the equivalent phase shift of realizing various complexity, and its performance with truly warble and true phase shift in full accord.

Equivalent chirp technology guarantees that fully single order equivalent chirp, second order equivalence chirped grating, high-order equivalence chirped grating etc. can separately obtain.Dai Yitang, people such as Chen Xiangfei are at Chinese invention patent " sampling optical fiber grating that DS-OCDMA system coding decoding is used and preparation method thereof " [200410009546.X, publication number: CN1588150 and document " Prague sampling period obtains equivalent phase shift in the employing change Fiber Bragg Grating FBG " [Yitang Dai, XiangfeiChen et.al, " Equivalent phase shift in a fiber Bragg grating achieved by changingthe sampling period ", IEEE Photon.Tech.Lett., vol.16, pp.2284-2286,2004] in the equivalent phase shift notion has been proposed.Dai Yitang, people such as Chen Xiangfei are at Chinese invention patent " a kind of method for producing multiple channel filter based on fiber grating " [CN200410083938.0] and document " employing reconstruct and equivalent chirp method; can obtain the sampling Bragg grating of predetermined response in a channel " [Yitang Dai, Xiangfei Chen et.al, " Sampled Bragg grating with desired response in one channel by use of areconstruction algorithm and equivalent chirp ", Opt.Lett., vol.29,1333-1335,2004] in a kind of design is proposed and making has method and the technology that any physical can realize the equivalent grating of filtering characteristic.This technology is a kind of new technology in conjunction with reconfiguration technique and equivalent chirp technology, and we are referred to as reconstruct-equivalent chirp technology (REC technology).Use reconstruct-equivalent chirp technology, on the common experiment porch of sub-micrometer precision, can and produce equivalent grating according to required design with various complex characteristics.

Yet, when reconstruct-equivalent chirp technology obtains the major application prospect, also have two intrinsic weakness.The first, reconstruct-equivalent chirp technology generally adopts+1 (or-1) level shadow grating, and under identical index modulation situation, its effective grating intensity only has 32% of even DFB structure fringe.Reach identical grating intensity, can only increase index modulation or prolong grating length.Second, the sampling structure of reconstruct-equivalent chirp technology can be introduced a plurality of shadow gratings, and only have wherein+1 (or-1) level shadow grating be used, and all the other each shadow gratings, especially 0 grade and-1 (or+1) grade shadow grating can produce very big negative effect to device performance.For example, in fiber laser, need to introduce equivalent chirp, significantly to reduce sharp possibility of penetrating such as its 0 grade based on reconstruct-equivalent chirp technology.These two intrinsic weakness make reconstruct-equivalent chirp technology in the process of the device of realizing excellent performance, need use higher index modulation and introduce complicated chirp structure than common Bragg grating device.

Three, summary of the invention

The objective of the invention is to propose a kind of sampling Bragg grating based on reconstruct-equivalent chirp technology, especially the sampling grating method for making of secondary and multiexposure, multiple exposure, combine with the holographic exposure technology, be applied to various optical fiber and slab guide in interior optical waveguide, in all kinds of optical waveguides, produce have secondary and a multiexposure, multiple exposure more than the secondary and the variable duty cycle sampling grating, realize the selection and the intensity adjustment of any channel.According to real needs, design the channelling mode and the intensity size that need, with the method realization of secondary and multiexposure, multiple exposure.Overcome two intrinsic weakness that reconstruct-equivalent chirp technology exists.

The present invention is based on the sampling Bragg grating of reconstruct-equivalent chirp technology, it is the fiber waveguide device that utilizes the holographic exposure technology to form, each sampling of this sampling Bragg grating is divided into equidistant m part, n part (n=0 in each sampling, 1 ..., phase place m-1) is n * (during 2 π/m), the active strength maximum of 1 grade of shadow grating of this sampling grating is the even m/ π * sin of Bragg grating (π/m) * 100%; Perhaps the phase place of the n part in each sampling be-n * (during 2 π/m), the active strength maximum of-1 grade of shadow grating of this sampling grating is the even m/ π * sin of Bragg grating (π/m) * 100%.

Double exposure technique (double-exposure), promptly a sampling interval be divided into equal in length two parts, write the Bragg grating of two kinds of outs of phase.For example, be 0.5 keeping dutycycle (in a sampling interval, first kind of phase grating accounts for the ratio of total length), the control phase relation, can regulate arbitrarily 0 grade with ± 1 grade magnitude relationship.For example, when two kinds of Bragg grating phase differential are π, 0 grade and other all even levels disappear, and ± 1 grade of intensity reaches maximal value, for 64% of even DFB structure fringe, are the twices of single exposure sampling grating ± 1 grade intensity.In addition, when the double exposure phase differential be 0.639 π, 0 grade is identical with ± 1 grade of intensity.

Multiple exposure technique is about to a sampling interval and is divided into many parts, writes the Bragg grating of out of phase respectively, regulates by the Bragg grating phase place to zones of different, and shadow grating intensities at different levels are controlled.

In three exposure techniques (triple-exposure), it is right-1,0 to realize, any adjustment of 1 grade of shadow grating.For example, three parts that a sampling interval are divided into equal in length, every partial-length equals 1/3 of sampling length, according to 0,2/3 π, 4/3 π phase place is exposed to it successively, form phase place and be respectively 0,2/3 π, the Bragg grating of 4/3 π, can eliminate-1 and 0 grade, and make 1 grade intensity bring up to 83% of even DFB structure fringe.

In four exposure techniques (quadruple-exposure), can realize any adjustment of right-4 ,-3 ,-2 ,-1,0,1,2,3,4 grades of shadow gratings.For example, a sampling interval is divided into four parts of equal in length, every partial-length equals 1/4 of sampling length, according to 0,0.5 π, π, 1.5 π phase places are exposed to it successively, form phase place and be respectively 0,0.5 π, π, the Bragg grating of 1.5 π, can eliminate in-4 to 4 grades 7 grades of all the other except-3 and 1 grades, and make 1 grade intensity bring up to 90% of even DFB structure fringe.Promptly, write the Bragg grating of four kinds of outs of phase in four parts of a sampling interval.Phase place between the Bragg grating that four parts comprise is 0,1/2 π, and π during 3/2 π, can eliminate in-4 to 4 grades 7 grades of all the other except-3 and 1 grades, and make 1 grade intensity bring up to 90% of even DFB structure fringe; Or the phase place between the Bragg grating that comprises of four parts is 0 ,-1/2 π ,-π, during-3/2 π, can eliminate in-4 to 4 grades except 3 and-1 grade all the other 7 grades, and make-1 grade intensity bring up to 90% of even DFB structure fringe.

Inventing described sampling Bragg grating can be Fiber Bragg Grating FBG or slab guide Bragg grating.

Based on the dual laser of described sampling Bragg grating, grating can write on the Active Optical Fiber, i.e. Er-doped fiber or Er Yb co-doped fiber.Phase differential between the re-expose is π.

The sampling grating technology of more general realization multiexposure, multiple exposure is: each sampling of sampling Bragg grating is divided into uniform m part, it is respectively n * (2 π/m) that method by similar above-mentioned phase shift and exposure makes the phase place of the grating of every part, (n=0,1,2, ..., m-1), can be in that (m+1) level be eliminated all grades except that 1 grade to the m level.And the intensity that makes 1 grade is brought up to m/ π * sin (π/m) * 100% of even DFB structure fringe.

The concrete method for making of double exposure technique is among the present invention, in sampling Bragg grating, determine dutycycle, at first on whole sampling grating all in sampling period first write grating, write the grating of another phase place afterwards in all the other zones that do not write grating.

The method of variable duty cycle is used to realize the toe of cutting of sampling grating, " sampling optical-fiber grating of variable duty cycle and apodization thereof ", Chinese invention patent ZL02117328.1, the realization of this method equivalence by each section length in the sampling range is to the control of exposure intensity, thereby realization is to the toe of cutting of sampling grating.For example, can be along the grating distribution arrangement, to the FUNCTION MODULATION (for example cosine function or Gaussian function) in addition of the first's width in the sampling interval, remaining then partial width is adjusted in proportion.

The concrete method for making of three exposure techniques is among the present invention, in sampling Bragg grating, determines the ratio of three exposed portions, writes the grating of out of phase respectively.

The concrete method for making of four exposure techniques is among the present invention, in sampling Bragg grating, determines the ratio of four exposed portions, writes the grating of out of phase respectively.

This method is widely used in the various devices that contain sampling Bragg grating except that being applicable to based on reconstruct-equivalent chirp technology device.

This method can be applicable on the dual wavelength DFB fiber laser, and optical fiber is Er-doped fiber or Er Yb co-doped fiber.

This method also is widely used in pure gain coupling semiconductor laser except that being applicable to pure index-coupled semiconductor laser, and gain coupling index-coupled hybrid coupled N-type semiconductor N laser instrument.

Beneficial effect of the present invention is: by the design and the method that propose twice or multiexposure, multiple exposure is made sampling Bragg grating, in order to overcome above two problems simultaneously, made the reconstruct-the most great qualitative leap of equivalent chirp technology realization since being born.

Four, description of drawings

Fig. 1: based on the traditional sampling modulation transmission spectrum synoptic diagram of reconstruct-equivalent chirp technology

Fig. 2: based on the double exposure transmission spectrum synoptic diagram of reconstruct-equivalent chirp technology

Fig. 3: based on three exposure transmission spectrum synoptic diagram of reconstruct-equivalent chirp technology

Fig. 4: based on four exposure transmission spectrum synoptic diagram of reconstruct-equivalent chirp technology

Fig. 5: based on the re-expose transmission spectrum of reconstruct-equivalent chirp technology, the phase differential between the double exposure is 0.8 π

Fig. 6 is based on the structural representation of the dual laser of the re-expose grating of reconstruct-equivalent chirp technology

Fig. 7: based on the laser output spectrum of the re-expose dual laser of reconstruct-equivalent chirp technology

Five, embodiment

Ultimate principle of the present invention is as follows: the index modulation of sampling grating can be expressed as

For uniform sampling, sampling function s (z) is the one-period function, such as square wave, equally spaced a series of Gauss pulse or the like.By Fourier transform,

Then for each channel (shadow grating) in the sampling, its index modulation is

In the double exposure, be in the sampling of P in the sampling period, two sections sampling intervals lay respectively at 0～P ₁,, P ₁～P.And the sampling function s (z) of two sections samplings equals A, B respectively.Then:

$F_m=\frac{1}{P}{\∫}_0^{P}S\left(z\right)\exp \left(\frac{-2\mathrm{m\πz}}{P/2}\right)\mathrm{dz}=\frac{1}{P}{\∫}_0^{P_1}\mathrm{Aexp}\left(\frac{-2\mathrm{m\πz}}{P/2}\right)\mathrm{dz}+\frac{1}{P}{\∫}_{P_1}^P\mathrm{Bexp}\left(\frac{-2\mathrm{m\πz}}{P/2}\right)\mathrm{dz}---\left(4\right)$

Work as P ₁=P/2 can obtain:

$\begin{array}{ccccc}{\mathrm{<figure-callout\; id="0"\; label="F"\; filenames="H2008102341842E00012.png"\; state="\{\{state\}\}">F</figure-callout>}}_0=\frac{A+B}{2}& F_{\&PlusMinus;1}=\frac{A-B}{\mathrm{j\&pi;}}& F_{\&PlusMinus;2}=0& F_{\&PlusMinus;3}=\frac{A-B}{3\mathrm{j\&pi;}}& F_{\&PlusMinus;4}=0\end{array}---\left(5\right)$

In traditional sampling grating is made, only to wherein one section expose i.e.: A=1; And other one section do not exposed, that is: B=0.Obtaining 0 grade of intensity this moment is that 50%, ± 1 grade of intensity of even Bragg grating is 32%.The projection of this moment is composed as shown in Figure 1: (all transmission spectrum synoptic diagram centre wavelengths are 1550nm among the present invention, and channel spacing is 1nm)

In the double exposure sampling grating that the present invention proposes, also expose for the second portion of each sampling interval, and and first form opposite phase: A=1, B=e ^{I π}=-1, at this moment, by formula (5), 0 grade of intensity is that 0, ± 1 grade of intensity is 64%.That is: 0 grade of disappearance.The spectrum synoptic diagram of this moment is Fig. 2:

In three exposures, be in the sampling of P in the sampling period, three sections sampling intervals lay respectively at 0～P ₁, P ₁～P ₂, P ₂～P.And the sampling function of three sections samplings is respectively A, B, C.Then:

$F_m=\frac{1}{P}{\&Integral;}_0^{P}S\left(z\right)\exp \left(\frac{-2\mathrm{m\&pi;z}}{P/2}\right)\mathrm{dz}$

(6)

$=\frac{1}{P}{\&Integral;}_0^{P_1}\mathrm{Aexp}\left(\frac{-2\mathrm{m\&pi;z}}{P/2}\right)\mathrm{dz}+\frac{1}{P}{\&Integral;}_{P_1}^{P_2}\mathrm{Bexp}\left(\frac{-2\mathrm{m\&pi;z}}{P/2}\right)\mathrm{dz}+\frac{1}{P}{\&Integral;}_{P_2}^P\mathrm{Cexp}\left(\frac{-2\mathrm{m\&pi;z}}{P/2}\right)\mathrm{dz}$

Work as P ₁=P/3, P ₂=2P/3 is to obtain:

${\mathrm{<figure-callout\; id="0"\; label="F"\; filenames="H2008102341842E00012.png"\; state="\{\{state\}\}">F</figure-callout>}}_0=\frac{A+B+C}{3}$

F±3＝0

If the phase place of three exposures is 0,2 π/3,4 π/3 respectively, promptly sampling function is: A=1, B=e ^{I2 π/3}, C=e ^{I4 π/3}, at this moment, by (7), in-4 to 4 grades, 0 grade ,-1 grade, 2 grades, ± 3 grades ,-4 grades of disappearances.1 grade of intensity is 83% of even Bragg grating.-2 grades of intensity are 41%.4 grades intensity is 21%.The spectrum synoptic diagram of this moment is Fig. 3:

In four exposures, be in the sampling of P in the sampling period, four sections sampling intervals lay respectively at 0～P ₁, P ₁～P ₂, P ₁～P ₃, P ₃～P.And the sampling function of four sections samplings is respectively A, B, C, D.Then:

$F_m=\frac{1}{P}{\&Integral;}_0^{P}S\left(z\right)\exp \left(\frac{-2\mathrm{m\&pi;z}}{P/2}\right)\mathrm{dz}=\frac{1}{P}{\&Integral;}_0^{P_1}\mathrm{Aexp}\left(\frac{-2\mathrm{m\&pi;z}}{P/2}\right)\mathrm{dz}+\frac{1}{P}{\&Integral;}_{P_1}^{P_2}\mathrm{Bexp}\left(\frac{-2\mathrm{m\&pi;z}}{P/2}\right)\mathrm{dz}$

(8)

$+\frac{1}{P}{\&Integral;}_{P_2}^{P_3}\mathrm{Cexp}\left(\frac{-2\mathrm{m\&pi;z}}{P/2}\right)\mathrm{dz}+\frac{1}{P}{\&Integral;}_{P_3}^P\mathrm{Dexp}\left(\frac{-2\mathrm{m\&pi;z}}{P/2}\right)\mathrm{dz}$

Work as P ₁=P/4, P ₂=P/4, P ₃=3P/4 can obtain:

${\mathrm{<figure-callout\; id="0"\; label="F"\; filenames="H2008102341842E00012.png"\; state="\{\{state\}\}">F</figure-callout>}}_0=\frac{A+B+C+\mathrm{<figure-callout\; id="4"\; label="D"\; filenames="H2008102341842E00011.png,H2008102341842E00012.png"\; state="\{\{state\}\}">D</figure-callout>}}{4}$

F±2＝0

F±4＝0 (9)

If the phase place of four exposures difference 0, π/4, pi/2,3 π/4, promptly sampling function is: A=1, B=e ^{The i pi/2}, C=e ^{I π}, D=e ^{The i3 pi/2}, at this moment, by (9), in-4 to 4 grades, 0 grade ,-1 grade, ± 2 grades, 3 grades, ± 4 grades of disappearances.1 grade of intensity is 90% of even Bragg grating.3 grades of intensity are 30%.The spectrum synoptic diagram of this moment is Fig. 4:

In three or four exposures, also can make the exposure phase differential for negative: 0 ,-2 π/3 ,-4 π/3 and 0 ,-π/4 ,-pi/2 ,-3 π/4.The spectrogram that obtains when spectrogram that obtain this moment and positive phase difference is about 0 grade of wavelength location minute surface symmetry.

In double exposure and multiexposure, multiple exposure, also can adjust its phase differential or each segment length, obtain inter-stage intensity relation arbitrarily.Adjust each segment length and also can make each segment length in the different sampling units also different, make and modulated, realize cutting toe (apolized), and need not the depth of modulation of Bragg grating itself is changed along the effective refractive index of grating orientation.

The grating of above-mentioned multiexposure, multiple exposure can be applicable to make dual wavelength DFB fiber laser, and for example the grating with Fig. 2 is engraved on the Active Optical Fiber, just forms dual wavelength DFB fiber laser, and optical fiber generally is Er-doped fiber or Er Yb co-doped fiber.Under the pumping at pump laser of active optical fiber, have enough gains, laser instrument will produce dual wavelength and swash and to penetrate.Dual wavelength fibre laser can produce at the photon of microwave, laser radar, and aspects such as Fibre Optical Sensor and the detection of bad border are used.

The use-pattern of the inventive method exemplifies:

Example (1) is inscribed grating at optical fiber, and traditional Ultra-Violet Laser scanning method is adopted in the inscription of grating.The method that writes the double exposure grating on optical fibre device is: at first write first's grating; With little platform (for example little platform that moves of PZT) travel(l)ing phase template of moving, the grating that interference fringe is write relatively for the first time produces phase differential; Write the next part grating again.The multiexposure, multiple exposure grating continues to write the grating of new phase place with little platform travel(l)ing phase template of moving on this basis.

Little calculation methods of length of moving is: travel(l)ing phase/2 π * grating cycle ∧.For example, in fiber grating, the grating cycle is 530nm, if need mobile π phase place, then uses little platform that moves to move 265nm and get final product.Fig. 5 is that phase shift is the transmission spectrum of the re-expose grating of 0.8 π, has introduced the equivalent phase shift of π at the center of grating.

Example (2) is inscribed grating on Er-doped fiber, traditional Ultra-Violet Laser scanning method is adopted in the inscription of grating.Grating is formed by re-expose, and the method that writes the double exposure grating is: at first write first's grating; With little platform (for example little platform that moves of PZT) travel(l)ing phase template of moving, the grating that interference fringe is write relatively for the first time produces phase differential π, writes the second portion grating again.The grating total length is 5 centimetres.Pumping laser is input in the grating, forms dual wavelength DFB fiber laser.The laser structure synoptic diagram as shown in Figure 6, the two laser of this laser instrument output, as shown in Figure 7, it is 6mW that dual wavelength swashs the threshold value of penetrating, Fig. 7 is the laser output spectrum when pumping light power is 75mW.

Claims (5)

1. sampling Bragg grating based on reconstruction-equivalent chirp technology, the fiber waveguide device that utilizes the holographic exposure technology to form, it is characterized in that each sampling of described sampling Bragg grating is divided into equidistant m part, n part in each sampling, n=0,1, ... m-1, phase place be that n * (2 π/m), the active strength maximum of 1 grade of shadow grating of this sampling grating are the even m/ π * sin of Bragg grating (∏/m) * 100%; Perhaps each sampling in the phase place of n part be-n * (2 π/m), the active strength maximum of-1 grade of shadow grating of this sampling grating are the even m/ π * sin of Bragg grating (∏/m) * 100%;

The described sampling Bragg grating that forms of twice holographic exposure wherein is divided into two parts of equal in length at a sampling interval, writes the described Bragg grating of two kinds of outs of phase; When the phase differential between the described Bragg grating that two parts comprise was π, 0 grade and every other even level shadow grating disappeared, and ± 1 grade of intensity reaches maximal value, for 64% of even DFB structure fringe, were the twices of single exposure sampling grating ± 1 grade intensity;

The sampling Bragg grating based on reconstruction-equivalent chirp technology that three holographic exposures form is divided into three parts of equal in length at a sampling interval, writes the described Bragg grating of three kinds of outs of phase; Phase differential between the described Bragg grating that three parts comprise is 0,2/3 π, during 4/3 π, eliminates-1 and 0 grade, and makes 1 grade intensity bring up to 83% of even DFB structure fringe; Or the phase differential between the described Bragg grating that comprises of three parts is 0 ,-2/3 π, during-4/3 π, eliminates 1 and 0 grade, and makes-1 grade intensity bring up to 83% of even DFB structure fringe;

The sampling Bragg grating based on reconstruction-equivalent chirp technology that four holographic exposures form is divided into four parts of equal in length at a sampling interval, writes the Bragg grating of four kinds of outs of phase; Phase differential between the described Bragg grating that four parts comprise is 0,1/2 π, π, during 3/2 π, eliminate-4 to 4 grades in except-3 and 1 grades all the other 7 grades, and make 1 grade intensity bring up to 90% of even DFB structure fringe; Or the phase differential between the described Bragg grating that comprises of four parts is 0 ,-1/2 π ,-π, during-3/2 π, can eliminate in-4 to 4 grades except 3 and-1 grade all the other 7 grades, and make-1 grade intensity bring up to 90% of even DFB structure fringe.

2. the sampling Bragg grating based on reconstruction-equivalent chirp technology according to claim 1 is characterized in that described sampling Bragg grating is Fiber Bragg Grating FBG or slab guide Bragg grating.

3. according to the described sampling Bragg grating of claim 2 based on reconstruction-equivalent chirp technology, it is characterized in that described Fiber Bragg Grating FBG writes on to form wave filter on the light-sensitive optical fibre, write on and form single wavelength or multiple-wavelength laser on the Active Optical Fiber; Described slab guide Bragg grating writes in index-coupled, gain coupling or the refractive index gain hybrid coupled semiconductor laser.

4. the sampling Bragg grating based on reconstruction-equivalent chirp technology according to claim 1, it is characterized in that adopting the method for variable duty cycle to realize the toe of cutting of sampling grating, the realization of equivalence is to the control of exposure intensity by each section length in the sampling range, thereby realizes the toe of cutting to sampling grating; Promptly along the grating distribution arrangement, to the FUNCTION MODULATION in addition of the first's width in the sampling interval, remaining then partial width is adjusted in proportion, writes the grating of out of phase.

5. a method for preparing the sampling Bragg grating based on reconstruction-equivalent chirp technology as claimed in claim 1 is characterized in that in sampling Bragg grating, determines each several part length ratio and raster phase, writes the each several part grating successively.

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