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技術領域 (請先閲讀背面之注意事項再填寫本頁) 本發明係關於光通訊，特別關於使用體繞射柵之光多 工器/解多工器中的極化靈敏器。 背景技藝 光纖光通訊開始時，典型上光纖係以單一波長載送單 頻道的資料。密集分波多工化（D W D Μ )使得給定波帶 內不同波長之多個頻道能夠於單模光纖上傳送，因而大幅 地增加每·一光纖可傳送的資料量。選取每一頻道.的波長， 以致於頻道不會彼此干擾且損耗於光纖之傳輸損耗會最小 。典型的D W D Μ允許由光纖同時傳送高達4 〇個頻道。 經濟部智慧財產局員工消費合作社印製 D W D Μ要求二觀念上對稱的裝置：多工器及解多工 器。多工器取得不同波長且來自不同光源之多個光東或光 頻道並將迨些頻道結合成單一的多頻道 或多色光束。 輸入典型上是諸如線性陣列的光纖、線性陣列的雷射二極 體或其它光源等線性陣列的波導。輸出典型上是諸如光纖 等單一波導。解多工器特別地將多色光根:據波長分離成分 別的頻道。輸入典型上是單一輸入光纖且輸出係典型上爲 諸如光纖或線性陣列光偵測器等線性陣列的波導。 爲了符合D W D Μ的需求，多工器及解多工器要求某 此闹有的特點。首先’色散裝置必須能夠提供緊密間隔頻 道局角度色散，以致於來自於多頻道或多工化的光之個別 頻道可以在相當短距離內充份地分別以便。與線性陣列的單 頻道光纖耦合。多工器及解多工器較佳地可互換，以致於 本纸張尺度適用中國國家標準（CNS ) Λ4規格（21〇χ297公着） -4- 487812 A7 B7 五、發明説明j ) (請先閲讀背面之注意事項再填寫本頁) 單…裝置能行多工化及解多工化功能（此處，「（解）多 工器」）。此外，（解）多工器必須能夠容納與光纖通訊 頻寬相當的自由頻譜範圍內之頻道。此外，裝置必須提供 高解析度以使串擾最小且必須進一步更高效率以使訊號損 失最小。理想的裝置也必須是小的、耐用的、不貴的、及 可依比例的。 經濟部智慧財產局員工消費合作社印製 相較於其它用於密集分波多工化應用而言，繞射光柵 爲基礎的多工器及解多工器具有相當低的成本、高產能、 低插入損耗及串擾、損耗均勻以及能夠同時多工化大數目 的頻道等顯著優點。代表性的繞射光柵爲基礎的（解）多 工器配置揭示於一起讓渡給申請人之2 0 0 0年7月2 9 日共同申請的美國專利申請序號09/628,774「Echelle Grating Dense Wavelength Division Multiplexer/Demultiplexer 」，其內容於此一倂作爲參考。但是，繞射光柵具有本質， 極化靈敏度而限制其（解）多工化應用之用途。亦即，經 由光纖之光訊號傳輸具有中間極化狀態，要求（解）多工 器實質地不敏感極化以使極化相關的損耗最小、取決於光 訊號的極化狀能之繞射效率的量測最少。 有很多種方法及裝置用於減少繞射光柵光纖（解）多 工器之極化靈敏度。Chowdhury之美國專利號 5， 966， 483 及 6， 0 9 7, 863(槪稱 Chowdhury )’其揭示於此一倂倂入參考，其說明具有縮減 的極化靈敏度之繞射光栅。C h 〇 w d h，u r y揭示藉由 使繞射光概反射面以閃耀角0 b定向以使波長A b的垂直 本紙張尺度適用中國國家標準（CNS ) Λ4規袼（210x297公 -5- 487812 A7 B7 五、發明説明j ) 入射光回射，以使極化靈敏度最小，波長λ b係與傳輸頻寬 Δ人的平均波長λ 不同。將閃耀角0 b選成第一與第二繞 射效率之間的差縮減在傳輸頻寬△ λ之內。此最小化繞射 效率差之解決之道由於限制閃耀角及閃耀波長的選取而具 有有限的用途，因而難以提供高解析度、最小串擾及小訊 號損耗之用於容納大數目的緊密間隔頻道的（解）多工器 之繞射光柵。TECHNICAL FIELD (Please read the notes on the back before filling out this page) The present invention relates to optical communications, and in particular to a polarization sensor in a light multiplexer / demultiplexer using a body diffraction grid. Background Art At the beginning of optical fiber optical communications, optical fibers typically carry a single channel of data at a single wavelength. Dense division multiplexing (DW DM) enables multiple channels of different wavelengths in a given band to be transmitted on a single-mode fiber, thereby greatly increasing the amount of data that can be transmitted per fiber. Select the wavelength of each channel, so that the channels will not interfere with each other and the transmission loss lost to the fiber will be minimal. A typical D W D M allows up to 40 channels to be transmitted simultaneously by fiber. Printed by the Consumer Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs, DW DM requires two conceptually symmetrical devices: a multiplexer and a demultiplexer. The multiplexer takes multiple light channels or channels from different light sources and combines them into a single multi-channel or multi-color beam. The input is typically a linear array of waveguides such as a linear array of fibers, a linear array of laser diodes, or other light sources. The output is typically a single waveguide such as a fiber. The demultiplexer specifically separates the multicolored light: separates the components into different channels according to the wavelength. The input is typically a single input fiber and the output is typically a linear array of waveguides such as a fiber or a linear array photodetector. In order to meet the requirements of DW DM, multiplexers and demultiplexers require certain features. First of all, a dispersion device must be able to provide closely spaced channel angular dispersion so that individual channels from multi-channel or multiplexed light can be sufficiently separated over a relatively short distance. Coupling with single-channel fiber of linear array. The multiplexer and demultiplexer are preferably interchangeable, so that this paper size applies the Chinese National Standard (CNS) Λ4 specification (21〇 × 297) -4- 487812 A7 B7 V. Description of the invention j) (Please Please read the notes on the back before filling this page) Single ... The device can perform multiplexing and demultiplexing functions (here, "(solution) multiplexer"). In addition, the (de) multiplexer must be capable of accommodating channels in a free spectrum range comparable to the bandwidth of fiber optic communications. In addition, the device must provide high resolution to minimize crosstalk and must be further more efficient to minimize signal loss. The ideal device must also be small, durable, inexpensive, and proportional. Printed by the Consumer Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs, compared with other applications for dense branched wave multiplexing, diffraction grating-based multiplexers and demultiplexers have relatively low cost, high productivity, and low insertion. Significant advantages such as loss and crosstalk, uniform loss, and the ability to multiplex a large number of channels simultaneously. A representative diffraction grating-based (solution) multiplexer configuration is disclosed in U.S. Patent Application Serial No. 09 / 628,774, jointly filed on July 29, 2000, to the applicant. "Echelle Grating Dense Wavelength Division Multiplexer / Demultiplexer ", the content of which is here for reference. However, diffractive gratings are inherently polarized, limiting their use in (de) multiplexed applications. That is, the optical signal transmission through the optical fiber has an intermediate polarization state, requiring (de) multiplexer to be substantially insensitive to polarization so as to minimize polarization-related losses, depending on the diffraction efficiency of the polarization-like energy of the optical signal The least amount of measurement. There are many methods and devices used to reduce the polarization sensitivity of the diffraction grating fiber (de) multiplexer. Chowdhury U.S. Patent Nos. 5,966,483 and 6,009,863 (hereinafter referred to as Chowdhury) ', which are incorporated herein by reference, describe diffraction gratings with reduced polarization sensitivity. C h 〇wdh, ury revealed that by orienting the diffractive light reflecting surface at a blazing angle 0 b, the wavelength A b is perpendicular to the paper size. This paper standard applies the Chinese National Standard (CNS) Λ4 Regulation 袼 (210x297 Public-5- 487812 A7 B7 V. Description of the invention j) The incident light is retroreflected to minimize the polarization sensitivity, and the wavelength λ b is different from the average wavelength λ of the transmission bandwidth Δ. The blaze angle 0 b is selected so that the difference between the first and second diffraction efficiencies is reduced within the transmission bandwidth Δλ. This solution to minimize the difference in diffraction efficiency has limited applications due to the limitation of the selection of the blaze angle and the blaze wavelength, so it is difficult to provide high resolution, minimum crosstalk and small signal loss for accommodating a large number of closely spaced channels (Solution) Diffraction grating of multiplexer.
Chowdhury又揭示藉由在繞射光柵之相鄰的反射步階 及上升部.之間設置凹及凸的角，以縮減繞射光柵極化靈敏 度。更特別地，Chowdhury揭示極化靈敏度可藉由改變相 鄰步階與上升部之間的凹角的半徑而縮減。雖然此揭示之 優點爲未對光柵之閃耀波長及閃耀角度作不必要的限定， 但是要準確地控制奈米級的凹部及凸部半徑是有困難且昂 貴。其也限制光柵的絕對效率。， ^Chowdhury also revealed that by setting concave and convex angles between adjacent reflection steps and rising portions of the diffraction grating, the polarization sensitivity of the diffraction grating is reduced. More specifically, Chowdhury revealed that the polarization sensitivity can be reduced by changing the radius of the concave angle between the adjacent steps and the rising portion. Although the advantage of this disclosure is that the blaze wavelength and blaze angle of the grating are not unnecessarily limited, it is difficult and expensive to accurately control the radius of the concave and convex portions of the nanometer level. It also limits the absolute efficiency of the grating. , ^
Chowdhury也揭示間距（或溝槽間隔）最大化有助於 使極化靈敏度最小化。但是，根據Chowdhury之揭示，操 縱閃耀角及閃耀波長以使極化靈敏度最小1，則此揭示會 限制光柵間距而使諸如D W D Μ訊號的適當頻道分離等繞 射光柵的其它重要目的劣化。Chowdhury also revealed that maximizing pitch (or trench spacing) helps minimize polarization sensitivity. However, according to Chowdhury's disclosure, manipulating the blaze angle and blaze wavelength to minimize the polarization sensitivity1, this disclosure will limit the grating pitch and degrade other important purposes of the diffraction grating, such as proper channel separation of the DW DM signal.
McMahon之美國專利號4，7 3 6， 3 6 0揭示體光 柵之極化靈敏器可藉由確保反射表面的寬度相較於光柵的 操作波長爲足夠大而最小化。這在效能上類似於C h 〇 w d h u r y 揭示的間距最大化。雖然此解決之道具有.有限的應用，但 是，其也對光柵設計選擇設下不必要的限制，因此，限制 本紙張尺度適用中國國家標準（CNS ) Λ4規格（210X297公釐） — -t : (請先閲讀背面之注意事項再填寫本頁)McMahon U.S. Patent No. 4,7 3,36 0 discloses that the polarization sensitivity of the bulk grating can be minimized by ensuring that the width of the reflective surface is sufficiently large compared to the operating wavelength of the grating. This is similar in efficiency to the maximization of the pitch revealed by C h 0 w d h u r y. Although this solution has limited applications, it also places unnecessary restrictions on the design of gratings. Therefore, this paper size is limited to the Chinese National Standard (CNS) Λ4 specification (210X297 mm) — -t: (Please read the notes on the back before filling this page)
、1T 經濟部智慧財產局員工消費合作社印製 -6 - 487812 A7 B7 五、發明説明‘) 了光柵對於具有緊密頻道間隔之訊號執行分波（解）多工 化之功能。 (請先閲讀背面之注意事項再填寫本頁) H e之美國專利號5，9 3 7， 1 1 3揭示另一方式 ，以使光波導繞射光柵之極化相關損耗最小。H e揭示繞 射光柵裝置，其具有設有多個預定光接收位置之輸出區。 第一平板波導區具有第一雙折射，第一平板波導區會與裝 置的輸入及輸出區光耦合。與第一平板波導區相鄰之第二 平板波導區具有預定的形狀及預定的形狀及預定尺寸，提 供不同於第一平板波導區之第二雙折射以提供極·化補償給 裝置。此解決之道要求提供第一及第二平板波導，因此無 法輕易地應用至體光裝置。在任何一情形中，提供至少二 平板波導會增加產品複雜度及成本。 經濟部智慧財1局員工消費合作社印製 另一縮減極化靈敏度之習知方法係提供極化分離器， 在極化分器之後係置於準直光件及光柵之間被分離的光束， 之一上的半波板。極化分離器會將入射光分離成第一及第 二光束，每一光束會延著不同的正交方向線性地極化。位 於一光束上的半波板會造成二光束均具有袖同的正交極化 。雖然此方法具有未限定繞射光柵的設計進而限制其執行 D W D Μ的用途之優點，但是，極化分光器及半波板傾向 於劣化（解）多工器的整個效率並增加構件及裝置的複雜 度。用於最小化極化靈敏度的極化分光器之用途係揭示於 Nlcla之美國專利號4，7 4 1, 5 8 8 ; Martin美國專利 號6，0 8 4，6 9 5 ; Doen·之美國專利號 5,8 0 9， 1 8 4 ;及 Boord 之 W〇 9 9 / 4 1 8 5 8 本紙張尺度適用中國國家梂準（CNS ) Λ4規格（210X297公釐） 487812 A7 B7 五、發明説明4 ) 本發明係爲克服上述問題 發明槪述 本發明的第一觀點係用於光通訊系統中多工化及解多 工化光訊號之繞射光柵。繞射光柵具有形成於基板中的多 個溝槽，每一溝槽均具有包含反射步階表面之溝槽表面。 溝槽表面又包含位在相鄰溝槽的反射步階表面之間的橫向 上升部。.反射塗層可爲導體金屬塗層，較佳地由.黃金組成 。或者，塗層可爲介電質，舉例而言，多層介電塗層。 本發明的另一觀點係製造光通訊系統中用於繞射光訊 號之反射繞射光柵。此方法包含在基板中形成多個平行溝 槽’平行溝槽包括步階及橫向上升部。於步階上但非上升 部上，設置反射塗層。以離子束濺射或反射塗著，將反射 塗層施加至溝槽而非上升部，或者，將反射塗層施加至步 階及上升部，然後，從上升部蝕刻反射塗層。反射塗層可 爲導體的金屬塗層，較佳地爲黃金。或者'塗層可爲介電 質’舉例而言，多層電塗層。 根據本發明之用於縮減繞射光柵的極化靈敏度之裝置 及方法允許閃耀角及光柵的溝槽間隔被選成最佳化諸如角 色散、整體效率及相當寬的頻寬上密集的頻道間隔（ 0 · 4 n m或更少）之解析度。然後在繞射光柵的反射步 階上而非上升部上設置反射導體塗層，以:;提供極化靈敏度 。或者’將介電塗層施加至步階及上升部二者上或僅施加 本纸張尺度適财關家料（CNS ) Λ4規格（210X297公釐） I -- 乙 ： (請先閲讀背面之注意事項再填寫本頁) 、11 經濟部智慧財產局員工消費合作社印製 -8- 487812 A7 ____B7 五、發明説明g ) 至步階。本發明允許極化靈敏度縮減而未增加利用繞射光 柵的多工器/解多工器之元件或複雜度且在材料上未限制 光柵設計選擇。實施本發明所需的繞射光柵之修改係次要 的且不昂貴的，基本上對光柵本身的成本或複雜度沒有影 響。 圖式簡述 圖1係習知繞射光柵的溝槽圖案輪廓； 圖2.係代表圖1的光柵步階的反射表面折射·之s極化 及P極化光的場強度爲離上升部的距離之函數； 圖3係根據本發明之具有導體反射塗層的步階之圖1 的繞射光柵之溝槽圖案的輪廓； 圖4係在光柵的整個表面上具有反射塗層之舉例說明 的繞射光柵之溝槽圖案的輪廓； 圖5係根據本發明之在上升部上未具有反射塗層的圖 4之繞射光柵的溝槽圖案之輪廓； 圖6係隨著圖4的光柵之折射的光訊a號的T Μ及T E 分量之選取頻寬內的波長函數而變之繞射效率的圖形；及 圖7係類似於圖6之圖形，顯示圖5之上升部上未具 有反射塗層的效果。 主要元件對照 1 〇 光柵 ： 1 2 基板 -9- (請先閱讀背面之注意事項再填寫本頁) 、1Τ 經濟部智慧財產局員工消費合作社印製 本紙張尺度適用中國國家梂準（CNS ) Λ4規格（210Χ297公釐） 487812 A7B7 經濟部智慧財產局員工消費合作社印製 五 、發明説明< ) 1 4 溝槽 1 6 平面步階 1 8 上升部 2 〇 頂點 2 2 金屬反射塗層 丄 〇， 光柵 1 6， 反射步階 1 8， 上升部 2 2， .反射塗層 2 8 繞射光柵 3 〇 溝槽 3 2 基板 3 4 橫向步階 3 6 上升部 3 8 平坦部 4 〇 反射塗層 2 8， 繞射光柵 3 4， 反射部 3 6， 上升部 3 8， 平坦部 4 0， 反射塗層 較佳實施例詳述 ： 圖1係習知的繞射光柵1 0之溝槽圖案的輪廓。光柵 本紙張尺度適用中國國家標準（CNS ) Λ4規格（210 X 297公釐〉 I -- -·“ 1(請先閲讀背面之注意事項再填寫本頁) -10- 487812 A7 B7 五、發明説明ί ) (請先閲讀背面之注意事項再填寫本頁) 1 0係由基板1 2組成，基板1 2具有形成於其中之多個 槽1 4。溝槽係由相鄰的橫向、平面步階1 6及上升部 1 8組成。平面步階1 6係反射表面，它們會反射入射光 。光柵用以接收如圖1的正弦波2 4.所示之入射光時，平 面上升部1 8係非反射表面，它們不反射入射光，。相鄰 的步階及上升部具有背離基板之頂點2 0，頂點在相鄰的 步階與上升部1 6、 1 8之間具有選取角度（α )。如圖 1所示，步階及上升部均具塗著導體反射塗層，典型上爲 諸如黃金等金屬反射塗層2 2。 經濟部智慧財產局員工消費合作社印製 在圖1中繪出正弦波2 4以代表極化的Τ Μ (橫向磁 )方向上（s )極化光的振盪電場。入射光會被反射離開 平面步階1 6的反射表面。此電場會在垂直於光柵溝槽及 垂直於上升部1 8的平面中振盪。（ρ )極化光的正交振 盪反射場或極化的Τ Ε (橫向電）方向會平行於光柵溝槽， 振盪。已知繞射光的Τ Ε及Τ Μ分量之繞射效率在繞射光 柵中是不同的。無意以此處所述的理論說明，限制本文獻 或申請專利範圍的範圍，但是至少部份說1極化光的正交 分量之不同繞射效率係因上升部表面上的導體塗層與電場 干擾。此現像在圖2中以圖形說明。圖2係Υ軸上的場強 度相對於離X軸上的上升部之距離。在上升部的場強度E s 爲零。相對地，與光柵的刻劃平行且垂直於（s )極化光 的平面之（P )極化光的電場向量不會取樣接近光柵上升 部的區域。因此，光栅上升部限定最少的:邊界條件且在上 升部Ε ρ # 〇。其係邊界條件的改變，相信此改變係增加光 本紙Γ張尺度適用中國國家標準（CNS ) Λ4規格（210X297公楚) ~ ~ 487812 Α7 Β7 五、發明説明4 ) 柵的極化相依性之一因素。 (請先閲讀背面之注意事項再填寫本頁) 圖3係說明圖1的光柵1 0之修改，用於最小化光柵 的極化相依損耗。光柵1 0 ’僅在反射步階1 6 ’上具有反射 塗層2 2 ’，且在上升部1 8 ’無反射塗層，上升部1 8 ’係 形成不反射入射光之非反射表面。這將不用由圖2中所示 的光柵上升部上的導體塗層設定邊界條件，因此，相信可 減少極化相依損失。 藉由不施加導體塗層至上升部而由消除上升部（或非 反射表面.）設定的邊界條件之另一方法係使用多層介電塗 層以取代圖1所示的習知實施例中的導體反射塗層2 2。 經濟部智慧財產局員工消費合作社印製 多層介電塗層可由此技藝中習知的一些高度反射多層介電 塗層中任一者製成，包含疊層的二氧化欽（T i〇2 )及二 氧化矽（S 1〇2 );疊層的五氧化鉅（T a 3〇5 )及二 氧化矽（S 1〇2 );及疊層的二氧化給（H f〇2 )及二， 氧化矽（S i〇2 )。多層介電塗層具有比簡單的金屬塗層 更高度反射之優點，可能超高9 9 . 9 %效率。由於這些 介電塗層需要爲非導體，所以，它們會確彳呆電場的T E及 T Μ分量取樣類似的邊界條件。因此，介電塗層的施加會 提供較高效率及減少的極化相關損失之潛能。如同圖3中 所示的導體反射塗層2 2 ’般，介電塗層也可僅施加至反射 表面。同樣地，可在採用諸如圖4及5中所示的反射導體 塗層之任何其它實施例或全息光柵（未顯示）中使用介電 塗層。 , 此處揭示的光柵可由數種習知的方法形成。舉例而言 本紙張尺度適用中國國家標準（CNS ) Α4規格(210Χ297公釐） 7Γ~ 一 487812 A7 B7 五、發明説明) (請先閲讀背面之注意事項再填寫本頁) ，其可由沈積於玻璃基板上的環氧樹脂層形成，在玻璃基 板中有界定溝槽之母模壓入於其中。溝槽也可以由以干涉 計的方式控制之分度機，直接於玻璃或矽基板中精確地力口 工。又一選擇係使用M c M a h ο η美國專利號 4,7 3 6, 3 6 0中所述的微縮影技術，其內容於此一 倂作爲參考。 以採用反射塗著材料之高度方向性光束（亦即，離子 束濺射）之塗著技術、或是以習知技術將整個光柵表面塗 著反射塗層並以離子蝕刻上升部（或非反射表面）之塗層 ，僅對步階（反射表面）完成塗著。雖然如同上述之介電 塗層可以是較佳的，但是，反射塗層可爲任何適當的反射 材料，且典型上爲諸如黃金等金屬導體反射塗層。 雖然下述實施例係說明在光柵的反射步階上設置反射 塗層但不在上升部上設置反射塗層可以有效減少極化相關， 損失，但是，並非要限定揭示之範圍。 經濟部智慧財產局員工消费合作社印紫 圖4係繞射光柵2 8的溝槽圖案之輪廓。光柵係由形 成於基板3 2中的多個溝槽3 0組成。每一溝槽係由橫向 步階3 4及上升部3 6所界定，橫向步階3 4及上升部 3 6係於溝槽中以平坦部3 8接合。在本實施例中，包含 反射步階3 4、平坦部3 8及上升部3 6之溝槽的整個表 面會由黃金的導體反射塗層4 0覆蓋。溝槽密度係每毫米 1 7 1 · 4溝槽、閃耀角0 b係3 1 ° 、溝槽深度約 2 5 0 ◦ · 〇 n m ’ 平坦部 3 8 約 7 1 3 ; · 0 n m，且頂 點角度α ,,是8 0 ° 。 本紙張尺度適用中國國家標準（CNS ) A4規格（210X297公釐） -13- 487812 Α7 Β7 五、發明説明L ) 圖5係繞射光柵2 8 ’的溝槽圖案之輪廓，其除了上升 部3 6 ’不具有導體反射塗層4 0 ’之外，在各方面均與繞射 光柵2 8相同。因此，僅有反射部階及平坦部3 8 ’係經過 塗著的光柵表面之部份。 圖6係效率相對於被折射之光訊號的T E及T Μ分量 的波長之圖形，光訊號係波長之函數。效率係個別的Τ Ε 及Τ Μ分量之繞射光的能量與入射於光柵上的光之能量的 比例。對於目前用於光通訊之C頻帶波長（λ = 1 5 2 8 . —1 5 6. 5 )而言，以TE與TM成份之間的效率差量測 之極化相關損失係在約1 0 - 1 6 %之間變化。 圖7係顯示圖5中所示的光柵2 8 ’之極化相關損失， 其中僅有反射步階3 4 ’被塗著。此處，極化相關損失明顯 減少，在約2 · 5 — 5 %之間變化。 ’ 根據本發明，不在光柵的上升部上設置反射塗層， ♦ 會減少體繞射光柵固有的極化相關損失。其並未要求可能 不利於光柵能力之光柵輪廓改變，以提供需要的頻道分離 、解析度及效率。使用介電反射塗層可以:造成類似的優點 。此外，以最少的代價及花費，可將這些優點提供給包含 但不限於此處所述的實施例等習知的光柵輪廓及全息光栅 本紙張尺度適用中國國家榡準（CNS ) Α4規格（210X29*7公釐） I ^裂-- -* * - (請先閱讀背面之注意事項再填寫本頁) ，1Τ 經濟.部智慧財產局員工消費合作社印製 -14-Printed by the Consumer Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs of the Ministry of Economic Affairs of the People's Republic of China. -6-487812 A7 B7 V. Description of the invention ‘) The grating performs the function of demultiplexing (de) multiplexing the signals with tight channel spacing. (Please read the notes on the back before filling out this page) US Patent No. 5,9 3 7, 1 1 3 of He discloses another way to minimize the polarization-dependent loss of the optical waveguide diffraction grating. He discloses a diffraction grating device having an output region provided with a plurality of predetermined light receiving positions. The first slab waveguide region has a first birefringence, and the first slab waveguide region is optically coupled to the input and output regions of the device. A second slab waveguide region adjacent to the first slab waveguide region has a predetermined shape and a predetermined shape and a predetermined size, and provides a second birefringence different from the first slab waveguide region to provide polarization compensation to the device. This solution requires the provision of first and second slab waveguides, so it cannot be easily applied to bulk light devices. In any case, providing at least two slab waveguides will increase product complexity and cost. The Consumer Cooperative of the Bureau of Intellectual Property, No. 1 Bureau of the Ministry of Economic Affairs, printed another conventional method for reducing polarization sensitivity. A polarization splitter is provided, and the polarized beam splitter is placed between the collimated light and the light beam separated by the grating. Half wave board on one. The polarization splitter splits the incident light into first and second beams, and each beam is linearly polarized in different orthogonal directions. A half-wave plate on one beam will cause the two beams to have the same orthogonal polarization. Although this method has the advantage of not limiting the design of the diffraction grating and thus limiting its use for performing DWD Μ, polarization beam splitters and half-wave plates tend to degrade (solve) the overall efficiency of the multiplexer and increase the component and device the complexity. The use of a polarization beam splitter for minimizing polarization sensitivity is disclosed in U.S. Patent No. 4,7 4 1,5 8 8 to Nlcla; U.S. Patent No. 6,0 8 4,6 9 5 to Martin; U.S. Doen Patent No. 5,8 0 9, 1 8 4; and Boord's W09 9/4 1 8 5 8 This paper size is applicable to China National Standard (CNS) Λ4 specification (210X297 mm) 487812 A7 B7 V. Description of the invention 4) The present invention is to overcome the above problems. The first aspect of the present invention is a diffraction grating used for multiplexing and demultiplexing optical signals in an optical communication system. The diffraction grating has a plurality of grooves formed in the substrate, and each groove has a groove surface including a reflective step surface. The trench surface in turn includes lateral rises between the reflective step surfaces of adjacent trenches. The reflective coating may be a conductive metal coating, preferably composed of gold. Alternatively, the coating may be a dielectric, for example, a multilayer dielectric coating. Another aspect of the present invention is to manufacture a reflection diffraction grating for diffracted light signals in an optical communication system. This method includes forming a plurality of parallel trenches in the substrate. The parallel trenches include steps and lateral rises. On the step but not the rising part, a reflective coating is provided. By ion beam sputtering or reflective coating, a reflective coating is applied to the grooves instead of the rising portions, or a reflective coating is applied to the steps and the rising portions, and then the reflective coating is etched from the rising portions. The reflective coating may be a metallic coating of the conductor, preferably gold. Or the 'coating may be a dielectric', for example, a multilayer electrical coating. The device and method for reducing the polarization sensitivity of a diffraction grating according to the present invention allows the blaze angle and the groove spacing of the grating to be selected to optimize such as dense channel spacing, overall efficiency and dense channel spacing over a fairly wide bandwidth (0 · 4 nm or less) resolution. Then, a reflective conductor coating is provided on the reflection step of the diffraction grating instead of on the rising portion to :; provide polarization sensitivity. Or 'Apply a dielectric coating to both the step and the rising part or only the paper size CNS Λ4 specification (210X297 mm) I-B: (Please read the back Please fill in this page again for attention) 11 Printed by the Consumer Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs -8-487812 A7 ____B7 V. Description of the invention g) To the step. The invention allows the polarization sensitivity to be reduced without increasing the components or complexity of the multiplexer / demultiplexer using a diffractive grating and without restricting the choice of grating design in material. Modifications to the diffraction grating required to implement the present invention are minor and inexpensive, and have essentially no effect on the cost or complexity of the grating itself. Brief Description of the Drawings Figure 1 shows the outline of the groove pattern of a conventional diffraction grating; Figure 2. The field intensity of the s-polarized and P-polarized light representing the reflective surface refraction of the grating steps of FIG. 1 is away from the rising part As a function of the distance; Figure 3 is the outline of the groove pattern of the diffraction grating of Figure 1 according to the steps of a conductive reflective coating according to the invention; Figure 4 is an illustration of a reflective coating on the entire surface of the grating The outline of the groove pattern of the diffraction grating of FIG. 4; FIG. 5 is the outline of the groove pattern of the diffraction grating of FIG. 4 without the reflective coating on the rising part according to the present invention; A graph of the diffraction efficiency of the refracted optical signal a of the T M and TE components as a function of the wavelength in the selected bandwidth; and FIG. 7 is a graph similar to that in FIG. 6, showing that the rising part of FIG. 5 does not have Effect of reflective coating. Comparison of main components 1 〇 Grating: 1 2 Substrate-9- (Please read the precautions on the back before filling out this page), 1T Printed by the Intellectual Property Bureau Staff Consumer Cooperatives of the Ministry of Economic Affairs This paper is applicable to China National Standards (CNS) Λ4 Specifications (210 × 297 mm) 487812 A7B7 Printed by the Consumer Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs 5. Description of the invention <) 1 4 Groove 1 6 Plane step 1 8 Rising part 2 〇 Vertex 2 2 Metal reflective coating 丄 〇, Grating 16, reflection step 1 8, rising part 2 2, reflective coating 2 8 diffraction grating 3 〇groove 3 2 substrate 3 4 lateral step 3 6 rising part 3 8 flat part 4 〇 reflective coating 2 8. Diffraction grating 3 4, reflective part 36, rising part 3 8, flat part 40, reflective coating. A detailed description of a preferred embodiment of the coating: FIG. 1 shows the outline of a groove pattern of a conventional diffraction grating 10 . The scale of this paper is applicable to the Chinese National Standard (CNS) Λ4 specification (210 X 297 mm> I--· "1 (Please read the precautions on the back before filling this page) -10- 487812 A7 B7 V. Description of the invention ί) (Please read the precautions on the back before filling out this page) 1 0 is composed of a substrate 1 2 which has a plurality of grooves 1 4 formed therein. The grooves are formed by adjacent lateral and planar steps 16 and the rising part 18. The plane step 16 is a reflective surface, which reflects the incident light. The grating is used to receive the incident light shown in Figure 4 of the sine wave 2 4. The plane rising part 18 series Non-reflective surfaces, they do not reflect incident light. Adjacent steps and rising parts have vertices 20 that are away from the substrate, and the vertices have a selection angle (α) between the adjacent steps and the rising parts 16 and 18. As shown in Figure 1, the step and rising sections are coated with a conductive reflective coating, typically a metallic reflective coating such as gold 2 2. Printed in Figure 1 by the Consumer Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs The sine wave 2 4 oscillates the polarization of the polarized light (s) in the TM (transverse magnetic) direction. The incident light will be reflected off the reflecting surface of plane step 16. This electric field will oscillate in a plane perpendicular to the grating groove and perpendicular to the rising portion 18. (ρ) The orthogonal oscillating reflection field of polarized light or The polarized T E (transverse electrical) direction will oscillate parallel to the grating groove. It is known that the diffraction efficiency of the T E and T M components of the diffracted light is different in the diffraction grating. It is not intended to use what is described here Theoretical explanations limit the scope of this document or patent application, but at least partly speaking, the different diffraction efficiency of orthogonal components of polarized light is caused by the interference of the conductive coating on the surface of the rising part and the electric field. This phenomenon is shown in Figure 2 Figure 2 illustrates the field strength. Figure 2 shows the field strength on the Y axis relative to the distance from the rising part on the X axis. The field strength E s at the rising part is zero. On the other hand, it is parallel to and perpendicular to the scale of the grating s) The plane of the polarized light (P) The electric field vector of the polarized light will not sample the area close to the rising part of the grating. Therefore, the rising part of the grating defines the least: boundary conditions and is at the rising part E ρ # 〇. It is the boundary Changes in conditions, I believe this change will increase the light The size of this paper is applicable to the Chinese National Standard (CNS) Λ4 specification (210X297 Gongchu) ~ ~ 487812 Α7 Β7 V. Description of the invention 4) One factor of the polarization dependence of the grid. (Please read the precautions on the back before filling in this (Page) Figure 3 illustrates the modification of the grating 10 of Figure 1 to minimize the polarization-dependent loss of the grating. The grating 1 0 'has a reflective coating 2 2' only at the reflection step 1 6 'and is rising The part 1 8 'has a non-reflective coating, and the rising part 18' forms a non-reflective surface that does not reflect incident light. This will not require the boundary conditions to be set by the conductive coating on the rising part of the grating shown in Figure 2. Therefore, it is believed Can reduce polarization dependence loss. Another method of removing the boundary conditions set by the rising portion (or non-reflective surface.) By not applying a conductive coating to the rising portion is to use a multilayer dielectric coating instead of the conventional embodiment shown in FIG. Conductor reflective coating 2 2. Multilayer dielectric coatings printed by employees ’cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs can be made from any of the highly reflective multilayer dielectric coatings known in the art, including laminated dioxin (Tio2) And silicon dioxide (S 102); stacked pentoxide (T a 3 05) and silicon dioxide (S 1 02); and stacked silicon dioxide (H f0 2) and two , Silicon oxide (Si02). Multi-layer dielectric coatings have the advantage of being more highly reflective than simple metal coatings, and may be 99.9% more efficient. Since these dielectric coatings need to be non-conducting, they will determine similar boundary conditions for sampling the T E and T M components of the electric field. Therefore, the application of a dielectric coating provides the potential for higher efficiency and reduced polarization-related losses. Like the conductive reflective coating 2 2 'shown in Fig. 3, the dielectric coating can also be applied only to the reflective surface. Likewise, a dielectric coating can be used in any other embodiment or holographic grating (not shown) employing a reflective conductor coating such as that shown in Figures 4 and 5. The gratings disclosed herein can be formed by several conventional methods. For example, this paper size applies Chinese National Standard (CNS) A4 specification (210 × 297 mm) 7Γ ~ 487812 A7 B7 V. Description of invention) (Please read the precautions on the back before filling this page), which can be deposited on glass An epoxy resin layer is formed on the substrate, and a female mold with a defined groove in the glass substrate is pressed into it. The grooves can also be indexed by an interferometer, and precisely machined directly in the glass or silicon substrate. Yet another option is to use the micrographic technique described in McMah, US Patent No. 4,7 3,3,60, the contents of which are hereby incorporated by reference. Coating technology using highly directional light beams (ie, ion beam sputtering) using reflective coating materials, or conventionally coating the entire grating surface with a reflective coating and ion-etching the rising portion (or non-reflective Surface), only the step (reflective surface) is completed. Although a dielectric coating as described above may be preferred, the reflective coating may be any suitable reflective material and is typically a metallic conductor reflective coating such as gold. Although the following embodiments are described to provide a reflective coating on the reflection step of the grating, but not to provide a reflective coating on the rising portion can effectively reduce polarization-related losses, but it is not intended to limit the scope of disclosure. Printed by the Consumer Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs. Figure 4 shows the outline of the groove pattern of the diffraction grating 28. The grating system is composed of a plurality of grooves 30 formed in the substrate 32. Each groove is defined by a lateral step 34 and a rising portion 36, and the lateral step 34 and the rising portion 36 are joined in the groove by a flat portion 38. In this embodiment, the entire surface of the trench including the reflection step 34, the flat portion 38, and the rising portion 36 is covered with a gold conductive reflective coating 40. The groove density is 17 1 · 4 grooves per millimeter, blazing angle 0 b is 3 1 °, the groove depth is about 2 5 0 ◦ · 〇nm 'flat portion 3 8 is about 7 1 3; 0 nm, and the apex The angle α, is 80 °. This paper size applies the Chinese National Standard (CNS) A4 specification (210X297 mm) -13- 487812 Α7 Β7 V. Description of the invention L) Figure 5 shows the outline of the groove pattern of the diffraction grating 2 8 ', except for the rising part 3 Except for 6 'without conductor reflective coating 40', it is the same as the diffraction grating 28 in every respect. Therefore, only the reflection step and the flat portion 3 8 ′ pass through the coated grating surface. Figure 6 is a graph of efficiency versus wavelength of the T E and T M components of the refracted light signal, and the light signal is a function of wavelength. Efficiency is the ratio of the energy of the diffracted light of the individual TE and TM components to the energy of the light incident on the grating. For the C-band wavelength (λ = 15 2 8. — 1 5 6. 5) currently used for optical communications, the polarization-dependent loss measured by the efficiency difference between the TE and TM components is about 10 -Change between 16%. Fig. 7 shows the polarization-dependent loss of the grating 2 8 'shown in Fig. 5, in which only the reflection step 3 4' is coated. Here, polarization-dependent losses are significantly reduced, varying between approximately 2.5-5%. ’According to the present invention, no reflective coating is provided on the rising portion of the grating, which will reduce the polarization-dependent losses inherent to the volume diffraction grating. It does not require grating profile changes that may be detrimental to the ability of the grating to provide the required channel separation, resolution, and efficiency. Using a dielectric reflective coating can: cause similar advantages. In addition, these advantages can be provided to the conventional grating contours and holographic gratings including but not limited to the embodiments described herein at the least cost and expense. The paper dimensions are applicable to China National Standards (CNS) A4 specifications (210X29 * 7mm) I ^--* *-(Please read the precautions on the back before filling out this page), printed by 1T Economy. Ministry of Intellectual Property Bureau Staff Consumer Cooperatives -14-