CN1256600C - Back incidence type high density quartz reflection grating - Google Patents
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- CN1256600C CN1256600C CN 200410052910 CN200410052910A CN1256600C CN 1256600 C CN1256600 C CN 1256600C CN 200410052910 CN200410052910 CN 200410052910 CN 200410052910 A CN200410052910 A CN 200410052910A CN 1256600 C CN1256600 C CN 1256600C
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Abstract
A back-incident high-density quartz reflection grating (TIR grating) for a dense wavelength division multiplexing device for common-use 1.55-micron optical fiber communication is characterized in that when the period of the grating is 660-740 nanometers, the depth of the grating is 680-820 nanometers, and the duty ratio of the grating is 1/2, the invention can enable the 1-level reflection diffraction efficiency to achieve a result higher than 95% for 1550 nanometer wavelength under the incidence of TM polarized light. When the period of the grating is 720-775 nanometers, the depth of the grating is 480-560 nanometers, and the duty ratio of the grating is 1/2, the invention has the advantages that: the 1 st order reflection diffraction efficiency at TE polarized light incidence can be made to achieve results above 96% for 1550 nm wavelength; the diffraction efficiency of the grating is irrelevant to the shape of the groove of the grating, and the duty ratio of the grating is 1/2; the back incident type high-density quartz reflection grating is processed by an optical holographic recording technology or an electron beam direct writing device combined with a microelectronic photoetching process, and can be produced in large batch at low cost.
Description
Technical field
The dense wave division multiplexer spare that this patent relates in the optical fiber telecommunications system is relevant, particularly a kind of quartzy reflection grating of back incident-type high density that is used for the dense wave division multiplexer spare of wave band 1.55 micron optical fibers communication commonly used.
Background technology
Along with the fast development of computer network, Wireless/wired communication, in continuous rising, optical fiber communication has advantages such as high capacity, low-loss, long-distance transmissions to people to the demand of communication bandwidth, is to satisfy the important technical that increases bandwidth demand fast.Dense wave division multipurpose (hereinafter to be referred as DWDM) technology improves multiplexing number of wavelengths by reducing the band separation of channel, can make full use of the bandwidth of an optical fiber resource, is the key core technology of optical fiber communication development.
The DWDM device mainly contains Thin Film Filter (Thin-film filter-is called for short TFF) at present, planar array waveguide grating (Arrayed waveguide grating-is called for short AWG) and free space diffraction grating several technical schemes such as (Free-spacediffraction grating-are called for short FSDG).
Thin Film Filter (TFF) mainly utilizes the mutual interference effect of light between multilayer film to realize frequency-selecting, each channel all needs an optical filter, further with intersect mixed the making of multiplexer (interleaver) and be used for improving the number of channel, because the pass band relatively flat is so many Thin Film Filters can stacked use be carried out filtering successively in a system.Yet TFF is owing to adopt the mode of filtering successively, and when energy consumption and failure rate rose thereupon, the reliability of total system descended thereupon; Although the optical property of single optical filter is good, if will realize the higher number of channel in the DWDM technology, the intersection of above-mentioned device uses the loss meeting that produces to weaken the wavelength-division/multiplexing performance of total system.And often on hundreds of layers, its corresponding coating technique cost is very high for the coating layers of optical filter; Additional intersection multiplexer, circulator (circulator) device of etc.ing expensive, feasible is that the cost of DWDM technology of representative device is very high with the Thin Film Filter.
AWG mainly utilizes the phase shift interference technology between the waveguide wave beam to realize the parallel multiplexing of light beam, adopts microelectric technique technology, integrated multipath channel on chip piece, integrated level height in the making.But AWG very easily is subjected to the influence of environment temperature, and its serviceability therefore changes, and it is worked under constant temperature.The string of interchannel can influence the raising of AWG integrated level around problem in addition.The wavelength response of general A WG multiplexing demultiplexing device is the Gaussian distribution form, and spectral response range is narrower, in case operation wavelength offset peak wavelength will be introduced bigger insertion loss.Although the AWG of the logical form of flat-top band can reduce the accurate control requirement to operation wavelength, needing increases other element, so still can introduce extra insertion loss.
FSDG has utilized the grating pair input beam to carry out the principle of diffraction, and each wavelength channel carries out wavelength-division or multiplexing corresponding to the unique angle of diffraction in space to each channel wavelength.Compare with TFF and AWG, FSDG can realize more channel of communication number, owing to be that incident light is carried out disposable interference filter, each channel simultaneously can walk abreast, so do not need to insert additional devices, affected by environment little, do not produce heat in the process of processing signals yet.And the FSDG temperature influence is little, produces more accurate phase shift than AWG, can further improve the number of channel, reduces polarization loss.Free space grating (FSDG) technology adopts the parallel processing mode, once just can realize the separation of interchannel or multiplexing, does not need to add the use of other device, just can reach the very high number of channel, make cost reduce, volume reduces, stability improves, and optical property is greatly improved.
FSDG mainly can be divided into metal grating and dielectric grating.Because there is absorption loss in metal, the diffraction efficiency of metal grating can not infinitely improve.The quartz transmission grating of high-diffraction efficiency needs very high score line density (more than 600 lines per millimeters), the degree of depth of grating also needs to reach 2 microns, its diffraction efficiency just may reach more than 90%, but so the quartzy preparing grating difficulty of high-aspect-ratio is big, needs to rely on the advanced deep etching technique of microelectronics.Though can further improve diffraction efficiency after the surface relief grating of light engraving erosion plates the dielectric reflective coating, the design of reflective coating and making are quite complicated.People such as J.R.Marciante have reported a kind of back incident-type grating (TIR grating) of novel high chromatic dispersion, see technology 1:J.R.Marciante et al. formerly, Opt.Lett.29,542 (2004), the type grating utilizes inner full-reflection effect (TIR, total internal reflection), be that light is during from optically denser medium directive optically thinner medium, if incident angle satisfies total reflection condition, then will there be transmitted light in the optically thinner medium, the energy of incident light all focuses on the reflected light.So-called back incident-type is meant that light is not front (one side that the grating groove is arranged) incident from grating, but from the back surface incident of grating substrate, by optimized choice to the grating cycle and the degree of depth, 1 grade of reflection diffraction efficiency of this back incident-type grating can reach more than 99.99%, almost near reflection fully.The advantage of TIR grating is that the flute profile of diffraction efficiency and grating is irrelevant; The direct optical grating construction that (often utilize quartzy) etches basse-taille shape on dielectric substance; Absorption loss is compared very little with metal; Because diffraction efficiency is very high, so need not plate high reflecting medium film at grating surface.
The present invention adopts the computation model of rectangular configuration grating.The diffraction theory of high dencity grating can not be explained by simple scalar optical grating diffraction equation, and must adopt the Maxwell equation of vector form and in conjunction with boundary condition, accurately calculate the result by calculation of coding machine program.People such as Moharam have provided the algorithm of rigorous coupled wave theory, see technology 2:M.G.Moharam et al. formerly, J.Opt.Soc.Am.A.12, and 1077 (1995), can solve the diffraction problem of this class high dencity grating.But as far as we know, also do not have at present to provide the quartzy reflection grating of back incident-type high density at 1.55 micron wavebands of optical fiber communication.
Summary of the invention
The technical problem to be solved in the present invention is that 1.55 micron waveband dense wave division multiplexer spares at optical fiber communication provide a kind of back incident-type high density quartzy reflection grating, this grating can TM realize the first order reflection diffraction efficiency greater than 95% or the TE polarization mode under realize that the first order reflection diffraction efficiency is greater than 96%.
Technical solution of the present invention is as follows:
A kind of quartzy reflection grating of back incident-type high density that is used for the dense wave division multiplexer spare of wave band 1.55 micron optical fibers communication commonly used, the cycle that is characterized in this grating is 660～740 nanometers, and the degree of depth of grating is 680～820 nanometers, and the dutycycle of grating is 1/2.The cycle of described grating is 685 nanometers, and the degree of depth of grating is the surface relief structure of 720 nanometers.
A kind of quartzy reflection grating of back incident-type high density that is used for the dense wave division multiplexer spare of wave band 1.55 micron optical fibers communication commonly used, its characteristics are that the cycle of this grating is 720～775 nanometers, the degree of depth of grating is 480～560 nanometers, and the dutycycle of grating is 1/2.The cycle of described grating is 740 nanometers, and the degree of depth of grating is the surface relief structure of 520 nanometers.
Foundation of the present invention is as follows:
Fig. 1 has shown the geometry of the quartzy reflection grating of back incident-type high density.Zone 1,2 all is uniformly, is respectively refractive index n
1=1.44462 quartz and refractive index n
2=1 air.Grating vector K is positioned at plane of incidence.The TM polarized incident light corresponding to the direction of vibration of magnetic vector perpendicular to the plane of incidence, the TE polarized incident light corresponding to the direction of vibration of electric field intensity perpendicular to the plane of incidence.The light wave of one linear polarization is θ at a certain angle
i=sin
-1(λ/(2* ∧)) incident is defined as the Littrow condition, promptly constitutes the condition that diffraction light returns along former incident direction of light, and λ represents incident wavelength, and ∧ represents the grating cycle.According to optical grating diffraction equation and total reflection condition, ∧ should satisfy condition
Under optical grating construction as shown in Figure 1, the present invention adopt technology 2 formerly the rigorous coupled wave Theoretical Calculation dutycycle be 1/2 quartzy grating under near the multi-wavelength light incident commonly used 1.55 microns of optical fiber communication, 1 grade of reflection diffraction efficiency, the result is referring to Fig. 2.We obtain as drawing a conclusion:
As shown in Figure 2, the incident light of TM polarization mode is with 51.55 ° of angles (corresponding to λ=1550 nanometers) when inciding the TIR grating, the cycle of this grating is 685 nanometers, the degree of depth is 720 nanometers, 1 grade of reflection diffraction efficiency is 100% (putting aside the absorption loss of medium) at 1550 nano wave length places, and promptly remains on more than 90% in the spectrum width scope of 88 nanometers in 1520-1607 nano wave length section.If all wavelengths of considering in the C+L wave band (1520-1620 nanometer) is separately with the Littrow angle incident of correspondence, the diffraction efficiency of all wavelengths all can reach more than 90%, promptly corresponding to the spectrum width scope of 101 nanometers.
As shown in Figure 3, the incident light of TE polarization mode is with 46.47 ° of angles (corresponding to λ=1550 nanometers) when inciding the TIR grating, the cycle of this grating is 740 nanometers, the degree of depth is 520 nanometers, 1 grade of reflection diffraction efficiency is 100% (putting aside the absorption loss of medium) at 1550 nano wave length places, and promptly remains on more than 90% in the spectrum width scope of 89 nanometers in 1520-1608 nano wave length section.If all wavelengths of considering in the C+L wave band (1520-1620 nanometer) is separately with the Littrow angle incident of correspondence, the diffraction efficiency of all wavelengths also all can reach more than 90%, promptly corresponding to the spectrum width scope of 101 nanometers.
Description of drawings:
Fig. 1 is the geometry of the multi-wavelength demultiplexing of the quartzy reflection grating of back incident-type high density of the present invention.
Fig. 2 is that quartzy reflection grating (refractive index of fused quartz gets 1.44462) the grating cycle of back incident-type high density of the present invention is 685 nanometers, the grating degree of depth 720 nanometers, dutycycle is 1/2, when the C+L of optical fiber communication wave band uses the TM polarized light with 51.55 ° of angle incidents (at the TIR grating of 1550 nano wave lengths) and each wavelength with corresponding Littrow angle incident (TIR (Littrow) grating) next stage reflection diffraction efficiency (%).
Fig. 3 is that quartzy reflection grating (refractive index of fused quartz gets 1.44462) the grating cycle of back incident-type high density of the present invention is 740 nanometers, the grating degree of depth 520 nanometers, dutycycle is 1/2, when the C+L of optical fiber communication wave band uses the TE polarized light with 46.47 ° of angle incidents (at the TIR grating of 1550 nano wave lengths) and each wavelength with corresponding Littrow angle incident (TIR (Littrow) grating) next stage reflection diffraction efficiency (%).
Fig. 4 is the recording beam path of holographic grating.
Embodiment
Utilize the micro-optic technology to make the high density rectangular raster, at first adopt the holographic recording mode to write down the grating (see figure 5): utilize He-Cd laser instrument (wavelength is 0.441 μ m) to send two bundle plane waves and on substrate, form interference field with 2 θ angles.We adopt the glass sheet that is coated with MICROPOSIT series 1818 photoresists as the record substrate, and ∧ represents the space periodic of grating, i.e. the spacing of adjacent stripes, its size is ∧=λ/(2*sin θ), wherein, λ is the recording light wavelength, adopts 0.441 μ m in experiment.Angle θ is big more for record, and then ∧ is more little, so by changing the size of θ, can control the cycle (periodic quantity can be designed by above-mentioned efficiency diagram) of grating, the record high dencity grating.Then, the pattern on the photoresist is transferred on the quartz substrate by microelectronics lithographic technique (wet-chemical or reactive ion dry etching), obtained the quartzy grating of high density surface embossment structure behind the flush away photoresist.
Table 1 has provided a series of embodiment of the present invention, and in making the process of grating, suitably the selective light grid cycle and the grating degree of depth just can obtain under the TM polarization mode back incident-type high density quartz reflection grating to the high-diffraction efficiency of 1550 nano wave lengths.
For example, be 685 nanometers when the cycle of TIR grating, when the degree of depth was 720 nanometers, the dutycycle of grating was 1/2, the first order reflection diffraction efficiency of grating is up to 100% (putting aside the absorption loss of medium).
Table 2 has provided a series of embodiment of the present invention, and in making the process of grating, suitably the selective light grid cycle and the grating degree of depth just can obtain under the TE polarization mode back incident-type high density quartz reflection grating to the high-diffraction efficiency of 1550 nano wave lengths.
For example, be 740 nanometers when the cycle of TIR grating, when the degree of depth was 520 nanometers, the dutycycle of grating was 1/2, the first order reflection diffraction efficiency of grating is up to 100% (putting aside the absorption loss of medium).
Among three kinds of wavelength division multiplex device technology TFF, AWG and the FSDG, free space diffraction grating (FSDG) has its unique advantage.One, FSDG and AWG all adopt parallel processing mechanism that light is carried out disposable filtering.Its two, FSDG has the highest channel capacity, be particluarly suitable for using among the DWDM, and the channel price is than minimum, and TFF is fit to work under the low number of channel, its number of channel can not infinitely increase.Its three, FSDG itself is no thermal device, and the temperature stability of AWG is poor, needs to use well heater make it be operated in constant temperature.Its four, FSDG has low insertion loss and polarization loss, and insertion loss and the polarization loss of AWG are higher.They are five years old, the element of FSDG is less, yield rate is high, component integration has potential development power (as photoswitch, scalable optical attenuator etc.), and TFF needs to be used with interleaver that performance descends when improving channel capacity, yield rate is low and is integrated undesirable, though the AWG element is few, temperature stability is a big problem.In a word, the free space diffraction grating is low with its polarization loss, to temperature-insensitive, parallel flat rubber belting filtering mode, can be used as a kind of desirable wavelength division multiplex device, and important application prospects is arranged in DWDM.
The quartzy reflection grating of back incident-type high density particularly of the present invention is during as wavelength division multiplex device, has very high reflection efficiency, do not need to consider the structure of grating flute profile, also needn't metal-coated membrane or deielectric-coating, can utilize holographic grating recording technique, microelectronics photoetching technique, can be in enormous quantities, produce at low cost, the grating stable performance after the etching, reliable is a kind of important realization technology of wavelength division multiplex device.
The following 1 grade of Prague transmission diffraction efficiency eta of table 1 TM polarization mode (%) [d is the grating degree of depth (nanometer), and ∧ is grating cycle (nanometer)]
The following 1 grade of Prague transmission diffraction efficiency eta of table 2 TE polarization mode (%) [d is the grating degree of depth (nanometer), and ∧ is grating cycle (nanometer)]
Claims (4)
1, a kind of quartzy reflection grating of back incident-type high density that is used for the dense wave division multiplexer spare of wave band 1.55 micron optical fibers communication commonly used, the cycle that it is characterized in that this grating is 660～740 nanometers, the degree of depth of grating is 680～820 nanometers, and the dutycycle of grating is 1/2.
2, the quartzy reflection grating of back incident-type high density according to claim 1, the cycle that it is characterized in that described grating is 685 nanometers, the degree of depth of grating is 720 nanometers.
3, a kind of quartzy reflection grating of back incident-type high density that is used for the dense wave division multiplexer spare of wave band 1.55 micron optical fibers communication commonly used, the cycle that it is characterized in that this grating is 720～775 nanometers, the degree of depth of grating is 480～560 nanometers, and the dutycycle of grating is 1/2.
4, the quartzy reflection grating of back incident-type high density according to claim 3, the cycle that it is characterized in that described grating is 740 nanometers, the degree of depth of grating is 520 nanometers.
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| CN 200410052910 CN1256600C (en) | 2004-07-16 | 2004-07-16 | Back incidence type high density quartz reflection grating |
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| CN100375912C (en) * | 2005-04-28 | 2008-03-19 | 北京印刷学院 | Method for making long-period optical fiber by employing electron beams |
| CN100359344C (en) * | 2006-01-18 | 2008-01-02 | 中国科学院上海光学精密机械研究所 | Quartz reflection polarization beam splitting grating with 1550 nanometer wavelength |
| CN105445835B (en) * | 2006-10-31 | 2021-07-27 | 莫迪里斯控股有限责任公司 | Lighting device and lighting system |
| CN108008478B (en) * | 2017-12-01 | 2022-09-09 | 暨南大学 | Polarization selection reflection type grating based on metal multilayer dielectric film |
| CN115217470B (en) * | 2022-07-19 | 2024-06-14 | 中国石油大学(华东) | Method for dividing and identifying driving factors of centimeter-micrometer scale gyros in shale |
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