TWI239412B - Optical directional coupler and design method thereof - Google Patents
Optical directional coupler and design method thereof Download PDFInfo
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1239412 五、發明說明（1) 發明之領域 一種光學方向耦合器，包含該方向耦合器之分光器 調制器、開關、極化分離器、可調式濾波器、波長多工 解多工器以及一種設計光學方向耦合器之耦合長度之方 法0 相關技術之說明 方向辆合器之結構係兩根長直波導以一定之間隙相 隔，如圖1係顯示習知方向耦合器1 0之結構圖。從理論 上可證明，當兩根波導的製作參數相同，且間隙夠小使耦 合效應夠強烈時，則光能量可從其中一根波導1 1耦合至 另一根1 2 ，其能量轉移關係如公式（1 )所示。1239412 V. Description of the invention (1) Field of the invention An optical directional coupler including a beam splitter modulator, a switch, a polarization splitter, a tunable filter, a wavelength multiplexing demultiplexer, and a design including the directional coupler. Method of the coupling length of the optical directional coupler 0 Description of related technology The structure of the directional coupler is that two long straight waveguides are separated by a certain gap, as shown in FIG. 1 is a structural diagram showing a conventional directional coupler 10. It can be theoretically proved that when the manufacturing parameters of the two waveguides are the same, and the gap is small enough to make the coupling effect strong enough, the optical energy can be coupled from one of the waveguides 1 1 to the other 1 2. The energy transfer relationship is as follows Equation (1) is shown.
Pj (z ) = P0 cos 2 {κζ )e P2(z)= p〇 sil] -az az 1 2(^> 公式（1) 其中，P〇係從波導輸入端輸入之總能量，Pi &P2係分別表 示波導#1及波導#2内部傳導之能量，/C係方向耦合器之兩 波導之麵合係數，α係表示波導本身之衰減常數，亦即波 導材質對光的吸收常數。 由公式（1 )中可看出，波導#1及波導#2内部傳導之能Pj (z) = P0 cos 2 {κζ) e P2 (z) = p〇sil] -az az 1 2 (^ > Formula (1) where P〇 is the total energy input from the waveguide input, Pi & P2 represents the internal conduction energy of waveguide # 1 and waveguide # 2, / C is the face-to-face coefficient of the two waveguides of the directional coupler, and α represents the attenuation constant of the waveguide itself, that is, the absorption constant of light by the waveguide material. It can be seen from the formula (1) that the internal conduction energy of the waveguide # 1 and the waveguide # 2
第4頁 1239412 五、發明說明（2) 量將隨著傳播距離改變而分別正比於cos2( /cz)及sin2( /c z)之函數，而其能量總合卩〆？）+ P2(z) = P〇cos2(/cz)e_a + P〇s i η 2 ( /c z ) e_ αζ二P〇e- αζ。若假設衰減常數甚小近似於 0，或傳播距離甚短使α ζ可忽略不計，則PJz) + P2(z)= P〇為一常數。故其最基本之應用即為一種一對二之分光 器，然現今已使用其原理應用於許多其它種積體光學元件 中，除作為分光器外，常用於調制器、開關、極化分離 器、可調式濾波器、波長多工一解多工器等等。 當方向耦合器作為開關時，其原理係應用電光效應改 變局部區域的折射率，使兩波導的傳播常數產生差異。該 元件需在波導搞合作用區鍍上電極，外加電壓調變兩波導 的輸出功率比值，故除作為光開關外，亦可作為相位調變 器及分光器。 當方向耦合器作為極化分離器時，係利用TE及TM方向 模態之傳播常數的不同，設計適當的耦合作用區長度使TE 及TM方向模態分離。當作為波長多工一解多工器使用時， 其原理類似，利用不同波長的不同傳播常數，經適當設計 之耦合作用區長度則可使不同波長之光線分離。 當方向耦合器作為可調式濾波器時，則需使兩波導的 寬度不一致，使其傳播常數亦不相同。接著鍍上電極，以 利用外加電壓調變光傳播常數。藉由外加電壓之電光效Page 4 1239412 V. Description of the invention (2) The quantity will be proportional to the function of cos2 (/ cz) and sin2 (/ c z) respectively as the propagation distance changes, and the total energy of them? ) + P2 (z) = Pocos2 (/ cz) e_a + Pois i η 2 (/ c z) e_ αζ two Poe-αζ. If it is assumed that the attenuation constant is very small and approximates 0, or that the propagation distance is so short that α ζ is negligible, then PJz) + P2 (z) = P0 is a constant. Therefore, its most basic application is a one-to-two optical splitter, but its principle has been used in many other integrated optical elements. In addition to being a spectroscope, it is often used in modulators, switches, and polarization splitters. , Tunable filters, wavelength multiplexing and demultiplexing, etc. When a directional coupler is used as a switch, its principle is to use the electro-optic effect to change the refractive index of a local area, so that the propagation constants of the two waveguides differ. This component needs to be plated with electrodes in the cooperation area of the waveguide, and the voltage can be used to modulate the output power ratio of the two waveguides. Therefore, it can also be used as a phase modulator and beam splitter in addition to being an optical switch. When the directional coupler is used as a polarization splitter, the TE and TM direction modes have different propagation constants, and an appropriate coupling action zone length is designed to separate the TE and TM direction modes. When used as a wavelength multiplexer and demultiplexer, the principle is similar. Using different propagation constants at different wavelengths and properly designed coupling action zone lengths can separate light at different wavelengths. When the directional coupler is used as a tunable filter, the widths of the two waveguides need to be different, so that their propagation constants are also different. Electrodes are then plated to modulate the light propagation constant with an applied voltage. Electro-optic effect by applying voltage
第5頁 1239412 五、發明說明（3) 應，可改變波導之傳播常數而形成可調式濾波器。 如上所述，方向耦合器之原理可廣泛地應用在各種積 體光學元件中，並可具有開關、調變及解調等功能，為光 通訊的重要元件。因此，值得吾人詳加研究。然而，方向 耦合器之缺點即在其耦合作用區過長，尤其應用在極化分 離器或波長多工解多工器時，其過長之耦合長度為元件積 體化之一大障礙。 發明之概要 因此，本發明之主要目的係解決上述方向耦合器之耦 合長度過長之問題。 本發明係揭示一種方向耦合器，其具有一對在橫截面 之面積相等且間隔等距離之光波導，其寬度係由輸入波導 之光波導寬度逐漸變小，再逐漸變大至輸出波導之光波導 寬度。此種方向耦合器之構造簡單，製程與習知方向耦合 器相同，但可使耦合長度縮減為習知方向耦合器的十分之 一或更小，有利於元件之積體化，提高方向耦合器之實用 性。與習知方向耦合器不同的是，不再採用兩長直波導， 而改用兩根寬度漸變之波導，其主要原理係藉由改變波導 之結構而改變波導之間之耦合係數，進一步改變所需之耦Page 5 1239412 V. Description of the invention (3) The tunable filter can be formed by changing the propagation constant of the waveguide. As mentioned above, the principle of the directional coupler can be widely used in various integrated optical components, and can have functions such as switching, modulation, and demodulation, and is an important component of optical communication. Therefore, it is worth studying in detail. However, the disadvantage of a directional coupler is that its coupling action area is too long, especially when it is applied to a polarization separator or a wavelength multiplexer / demultiplexer, and its excessively long coupling length is a major obstacle to the integration of components. SUMMARY OF THE INVENTION Therefore, the main object of the present invention is to solve the problem that the coupling length of the directional coupler is too long. The invention discloses a directional coupler, which has a pair of optical waveguides with equal cross-sectional area and equidistant spacing. The width of the optical waveguide is gradually reduced from the width of the input waveguide to the optical waveguide and then gradually increased to the output waveguide Waveguide width. The structure of this type of directional coupler is simple, and the manufacturing process is the same as the conventional directional coupler, but it can reduce the coupling length to one tenth or less of the conventional directional coupler, which is conducive to the integration of components and improves the directional coupling. Practicability. Unlike the conventional directional coupler, instead of using two long straight waveguides, two waveguides with gradually varying widths are used. The main principle is to change the coupling coefficient between the waveguides by changing the structure of the waveguides, further changing the Need coupling
第6頁 1239412 五、發明說明（4) 合長度而達到縮減粞合長度的目的。 此外，本發明係揭示一種光學方向耦合器，其具有複 數個橫截面之面積相等且間隔不等距離之光波導，其寬度 係由輸入波導之光波導寬度逐漸變小，再逐漸變大至輸出 波導之光波導寬度。 此外，本發明係揭示一種光學方向耦合器之設計方 法，該方向耦合器係具有一對在橫截面之面積相等且間隔 等距離之光波導，其寬度係由輸入波導之光波導寬度逐漸 變小，再逐漸變大至輸出波導之光波導寬度。 較佳實施例之詳細說明 接下來將參考附圖而詳細說明本發明之較佳實施例。 本發明係揭示一種方向耦合器，其具有一對在橫截面 之面積相等且間隔等距離之光波導，其寬度係由輸入波導 之光波導寬度逐漸變小，再逐漸變大至輸出波導之光波導 寬度。圖2係顯示一種本發明之方向耦合器2 0之結構 圖，其波導寬度係線性變化。圖3係顯示本發明另一種方 向耦合器3 0之結構圖，其波導寬度係呈曲線變化。本發 明之方向耦合器之構造簡單，製程與習知方向耦合器相Page 6 1239412 V. Description of the invention (4) Reduce the combined length by reducing the combined length. In addition, the present invention discloses an optical directional coupler having a plurality of optical waveguides with equal cross-sectional areas and unequal intervals. The width of the optical waveguide gradually decreases from the width of the input waveguide to the output waveguide and then gradually increases to the output. Waveguide's optical waveguide width. In addition, the present invention discloses a method for designing an optical directional coupler. The directional coupler has a pair of optical waveguides of equal cross-sectional area and equidistant intervals. The width of the directional coupler is gradually reduced by the width of the optical waveguide of the input waveguide. , And then gradually increase to the optical waveguide width of the output waveguide. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The invention discloses a directional coupler, which has a pair of optical waveguides with equal cross-sectional area and equidistant spacing. The width of the optical waveguide is gradually reduced from the width of the input waveguide to the optical waveguide and then gradually increased to the output waveguide light. Waveguide width. Fig. 2 is a structural diagram showing a directional coupler 20 of the present invention, and the waveguide width thereof varies linearly. Fig. 3 is a structural diagram showing another directional coupler 30 of the present invention, and the waveguide width thereof changes in a curve. The directional coupler of the present invention has a simple structure, and the manufacturing process is similar to that of a conventional directional coupler.
Η 第7頁 1239412 五、發明說明（5) 同，但可使耦合長度縮減為習知方向辆合器的十分之一或 更小，有利於元件之積體化，提高方向耦合器之實用性。 與習知方向耦合器不同的是，不再採用兩長直波導，而改 用兩根寬度漸變之波導，其主要原理係藉由改變波導之結 構而改變波導之間之耦合係數，進一步改變所需之耦合長 度而達到縮減耦合長度的目的。下文分別以兩種光波導基 板上兩種製程的實施例驗證本發明。 實施例一 實施例一係在二氧化矽基板上以薄膜沉積之方式製造 寬5微米，間隔5微米之光波導，該基板之折射率為1 . 5， 波導之折射率為1 . 5 2，折射率差為0 . 0 2，係一種低折射率 差之光波導。圖4係顯示本發明之方向耦合器之長度對波 導寬度最小值Wmin與波導寬度W之比值Wffiin/W的結果。圖5係 顯示本發明之方向耦合器傳輸效率對波導寬度最小值Wmin 與波導寬度W之比值Wmin/W的結果。在圖4及圖5中，實線 係表示波導寬度線性漸變之方向耦合器，短虛線係波導寬 度以三次曲線漸變之方向耦合器，而長虛線係波導寬度以 正弦曲線漸變之方向耦合器。由圖4及圖5之結果顯示， 當方向耦合器腰部之波導寬度最小值與波導寬度比Wmin/W 為0. 2時，線性、三次曲線及正弦曲線三種方向耦合器的 光傳輸效率分別為9 9 · 6 %、9 9 · 9 %及9 9 . 8 %，但此時之方向7 Page 7 1239412 V. Description of the invention (5) Same, but can reduce the coupling length to one tenth or less of the conventional directional coupler, which is conducive to the integration of components and improves the practicality of the directional coupler. Sex. Unlike the conventional directional coupler, instead of using two long straight waveguides, two waveguides with gradually varying widths are used. The main principle is to change the coupling coefficient between the waveguides by changing the structure of the waveguides, further changing the coupling coefficients. The required coupling length achieves the purpose of reducing the coupling length. In the following, the embodiments of the two processes of the two optical waveguide substrates are used to verify the present invention. Embodiment 1 Embodiment 1 is to fabricate an optical waveguide with a width of 5 micrometers and an interval of 5 micrometers on a silicon dioxide substrate by thin film deposition. The refractive index of the substrate is 1.5 and the refractive index of the waveguide is 1.52. The refractive index difference is 0.02, which is an optical waveguide with a low refractive index difference. Fig. 4 shows the result of the ratio of the length of the directional coupler of the present invention to the minimum value of the waveguide width Wmin and the ratio Wffiin / W of the waveguide width W. Fig. 5 shows the results of the transmission efficiency of the directional coupler of the present invention on the ratio Wmin / W of the minimum waveguide width Wmin and the waveguide width W. In Figs. 4 and 5, the solid line indicates a directional coupler in which the waveguide width linearly changes, the short dotted line indicates a directional coupler in which the waveguide width changes in a cubic curve, and the long dotted line indicates a directional coupler in which the waveguide width changes in a sine curve. The results shown in Figures 4 and 5 show that when the minimum waveguide width at the waist of the directional coupler and the ratio Wmin / W of the waveguide width are 0.2, the light transmission efficiency of the linear, cubic, and sinusoidal directional couplers is 9 9 · 6%, 9 9 · 9% and 9 9 8%, but the direction at this time
第8頁 1239412 五、發明說明（6) 耦合器之長度僅分別為習知方向耦合器的1 5. 0 % 9. 0 %，對元件積體化之改進甚大。 實施例 實施例二係在鈮酸鋰 米，間隔2微米之光波導· 折射率為2.32，折射率差 波導。圖6係顯示本發明 最小值Wfflin與波導寬度W之 發明之方向耦合器傳輸效 寬度W之比值Wmin/W的結果 波導寬度線性漸變之方向 次曲線漸變之方向耦合器 線漸變之方向耦合器。由 耦合器腰部之波導寬度最 時，線性、三次曲線及正 效率分別為9 9 . 5 %、9 9 · 9 % 之長度僅分別為習知方向 元件積體化之改進甚大。 基板上以質子交換法製造寬3微 ，該基板之折射率為2 . 2，波導之 為0.12，係一種高折射率差之光 之方向耦合器之長度對波導寬度 比值Wmin/W的結果。圖7係顯示本 率對波導寬度最小值Wmin與波導 。在圖6及圖7中，實線係表示 耦合器，短虛線係波導寬度以三 ，而長虛線係波導寬度以正弦曲 圖6及圖7之結果顯示，當方向 小值與波導寬度比Wmin/W為0. 1 弦曲線三種方向輛合器的光傳輸 及99.6%，但此時之方向耦合器 耦合器的3 · 4 %、2 · 1 %及1 · 4 %，對 接著，將揭示一種設計短耦合長度方向耦合器之方 法，該方法包含：決定輸入及輸出光波導之寬度、深度及Page 8 1239412 V. Description of the invention (6) The length of the coupler is only 15.0% 9.0% of the conventional directional coupler, which greatly improves the integration of components. EXAMPLES Example 2 is an optical waveguide based on lithium niobate at an interval of 2 microns. The refractive index is 2.32, and the refractive index difference is a waveguide. Fig. 6 shows the result of the invention's invention of the directional coupler with the minimum Wfflin and the waveguide width W. The result of the ratio Wmin / W of the width W. The directional coupler of the linear gradient of the waveguide width and the directional coupler of the linear curve. When the waveguide width of the coupler's waist is the maximum, the linear, cubic, and positive efficiencies are respectively 99.5% and 99. 9%. The lengths are only a significant improvement in the integration of conventional directional components. The substrate is manufactured by a proton exchange method with a width of 3 micrometers, the refractive index of the substrate is 2.2, and the waveguide is 0.12, which is a result of the ratio of the length of the directional coupler with a high refractive index difference to the waveguide width ratio Wmin / W. Figure 7 shows the minimum value of the ratio of waveguide to waveguide width, Wmin, and waveguide. In Figures 6 and 7, the solid line indicates the coupler, the short dashed line indicates the width of the waveguide by three, and the long dashed line indicates the width of the waveguide. The results are shown in Figures 6 and 7, when the direction value is smaller than the waveguide width ratio Wmin / W is the light transmission of 99.6% of the three directions of the chord coupler with a chord curve, but at this time, 3.4%, 2.1%, and 1.4% of the directional coupler couplers will be revealed. A method for designing a short coupling length direction coupler, the method includes: determining the width, depth and
第9頁 1239412 五、發明說明（7) 折射率；決定光耦合比例；決定該方向耦合器之漸變波導 形狀；積分該方向耦合器之耦合係數為第一耦合係數；計 算無漸變波導之方向耦合器之第二耦合係數；由該光耦合 比例及該無漸變波導之方向耦合器之第二耦合係數計算所 需之耦合長度為第二耦合長度；則該短長度方向耦合器所 需之第一耦合長度等於第二耦合長度乘以第二耦合係數除 以第一耦合係數；其中，該方向辆合器係具有一對在橫截 面之面積相等且間隔等距離之光波導，該光波導之寬度係 不固定的。 在本發明中，短耦合長度方向耦合器係一種波導寬度 漸變之方向耦合器，故其耦合係數將隨著波導寬度而改 變。因此，可將方向耦合器之耦合係數表示成公式（2)， ：(w) 2h2pe~ps β\Ψ+2,Page 9 1239412 V. Description of the invention (7) Refractive index; determine the optical coupling ratio; determine the shape of the gradual waveguide of the directional coupler; integrate the coupling coefficient of the directional coupler as the first coupling coefficient; calculate the directional coupling without the gradual waveguide The second coupling coefficient calculated from the optical coupling ratio and the second coupling coefficient of the directional coupler without the gradual waveguide is the second coupling length; then the first required by the short-length directional coupler The coupling length is equal to the second coupling length multiplied by the second coupling coefficient divided by the first coupling coefficient. Among them, the coupler in this direction has a pair of optical waveguides with equal cross-sectional area and equidistant intervals. Department is not fixed. In the present invention, the short-coupling-length-coupler is a directional coupler with a gradually changing waveguide width, so its coupling coefficient will change with the waveguide width. Therefore, the coupling coefficient of the directional coupler can be expressed as formula (2): (w) 2h2pe ~ ps β \ Ψ + 2,
2+Α2 7 公式（2) 其中，h及ρ係分別由下述之公式（3 )及公式（4 )所決定，而 W係波導寬度，s係方向耦合器兩分支波導之間距。 公式（3 ) 公式（4) 公式（5 )2 + Α2 7 Formula (2) where h and ρ are determined by the following formulas (3) and (4), respectively, and W is the width of the waveguide and s is the distance between the two branched waveguides of the directional coupler. Formula (3) Formula (4) Formula (5)
第10頁 1239412 五、發明說明（8) 2π其中，ns係基板之折射率，nf係波導之折射率， 之等效折射率，而AQ係傳播之光線在真空中之波長 公式（6 ) ff係波導 ，之 知需 得所 可得 中求 1_ 11 式式 公公 之用 上可 從即 後 例 比 光 分 之 欲 所 定 決 長 合 耦 短 之 明 發 本 工之 其需 然所 ，其 同， 不後 器例 合比 耦光 向分 方之 知欲 習所 與定 雖決 上在 構故 結是 在， 器致 合一 耦則 向理 方原 度作 L2 k{w0\lx = jh：(w)dz 〇 公式（7 ) 其中，WQ係表示習知方向耦合器之波導寬度，/c ( W。）係表 示波導寬度不變之習知方向耦合器之第一耦合係數/^，h 係在習知方向耦合器已知光耦合比例後所需之第一耦合長 度，而/c(W)係本發明之短耦合長度方向耦合器之耦合係 數，其表示耦合係數隨波導寬度漸變而變，L2則是本發明 之短耦合長度方向耦合器之第二耦合長度。因習知方向耦 合器之波導條件從輸入端至輸出端皆為一致，故可令第一 耦合係數q及第一耦合長度1^兩項直接相乘即可求得光耦 合比例，然本發明之短麵合長度方向搞合器之波導係漸變 的，故需以積分式表示之，然而其積分結果需與習知方向Page 10 1239412 V. Explanation of the invention (8) 2π where ns is the refractive index of the substrate, nf is the refractive index of the waveguide, the equivalent refractive index, and AQ is the wavelength of the light propagating in the vacuum formula (6) ff Department of waveguide, the knowledge needs to obtain what is available 1_ 11 The use of the formula can be used immediately from the light of the desire to determine the length and coupling of the short-cut Mingfa the work of the need, the same, However, the coupling between the coupling and coupling of the light to the knowledge and desire of the split party is determined by the reason. The coupling of the coupling to the coupling is L2 k {w0 \ lx = jh :( w) dz 〇 Formula (7), where WQ is the waveguide width of the conventional directional coupler, / c (W.) is the first coupling coefficient of the conventional directional coupler with constant waveguide width / ^, h is The first coupling length required after the known directional coupler knows the optical coupling ratio, and / c (W) is the coupling coefficient of the short coupling length directional coupler of the present invention, which indicates that the coupling coefficient changes with the gradual change of the waveguide width , L2 is the second coupling length of the short coupling length direction coupler of the present invention. Since the waveguide conditions of the conventional directional coupler are consistent from the input end to the output end, the first coupling coefficient q and the first coupling length 1 ^ can be directly multiplied to obtain the optical coupling ratio. The waveguide system of the short-face and length-direction coupler is gradual, so it needs to be expressed by the integral formula, but its integration result must be in accordance with the conventional direction.
第11頁 1239412 五、發明說明（9) 耦合器之相乘結果一致。 在公式（7)中，透過正規化代數變換，可令第二耦合 係數/c 2 1= \^)dzL 0 公式（8) 則公式（7 )可轉換成公式（9 ) 公式（9) 因此，可由L2 = Li * /Ci /c 2計算出L 2 最後，雖然已參考較佳實施例顯示並說明本發明，但 熟知此技術者將瞭解到，可在不違背由附加申請專利範圍 所定義本發明之實際精神及範疇下，進行各種形式及細節 之改變。例如，本發明之方向耦合器可使用在玻璃、塑 膠、矽或砷化鎵等基板上製成之光波導，或複數個光波導 之方向耦合器。Page 11 1239412 V. Description of the invention (9) The multiplication result of the coupler is the same. In formula (7), through the normalized algebraic transformation, the second coupling coefficient / c 2 1 = \ ^) dzL 0 Formula (8) Then formula (7) can be converted into formula (9) Formula (9) Therefore L 2 can be calculated from L 2 = Li * / Ci / c 2 Finally, although the present invention has been shown and described with reference to the preferred embodiments, those skilled in the art will understand that it can be defined without departing from the scope of the additional patent application In the actual spirit and scope of the present invention, various forms and details are changed. For example, the directional coupler of the present invention may use an optical waveguide made of a substrate such as glass, plastic, silicon, or gallium arsenide, or a directional coupler of a plurality of optical waveguides.
第12頁 1239412 圖式簡單說明 圖式簡單說明 圖1係顯示習知方向耦合器之結構圖。 圖2係顯示本發明一種方向耦合器之結構圖。 圖3係顯示本發明另一種方向耦合器之結構圖。 圖4係顯示本發明第一種實施例之方向耦合器之長度 對波導寬度最小值與波導寬度比的結果。 圖5係顯示本發明第一種實施例之方向耦合器傳輸效 率對波導寬度最小值與波導寬度比的結果。 圖6係顯示本發明第二種實施例之方向耦合器之長度 對波導寬度最小值與波導寬度比的結果。 圖7係顯示本發明第二種實施例之方向耦合器傳輸效 率對波導寬度最小值與波導寬度比的結果。 元件符號說明 0 方向耦合器Page 12 1239412 Brief description of the drawings Brief description of the drawings Figure 1 shows the structure of a conventional directional coupler. FIG. 2 is a structural diagram of a directional coupler according to the present invention. FIG. 3 is a structural diagram showing another directional coupler according to the present invention. Fig. 4 shows the results of the length of the directional coupler versus the minimum value of the waveguide width and the ratio of the waveguide width according to the first embodiment of the present invention. Fig. 5 is a graph showing the results of the transmission efficiency of the directional coupler with respect to the minimum value of the waveguide width and the ratio of the waveguide width according to the first embodiment of the present invention. Fig. 6 shows the result of the length of the directional coupler versus the minimum value of the waveguide width and the ratio of the waveguide width in the second embodiment of the present invention. Fig. 7 shows the results of the directional coupler transmission efficiency on the minimum value of the waveguide width and the ratio of the waveguide width in the second embodiment of the present invention. Component Symbol Description 0 Directional Coupler
II
I i 第13頁 1239412 圖式簡單說明 波導I i Page 13 1239412 Simple illustration of the waveguide
波導 輸入光 輸出光 方向輛合器 波導 波導 輸入光 輸出光 方向耗合器 波導 波導 輸入光 輸出光Waveguide input light output light directional coupler waveguide waveguide input light output light directional coupler waveguide waveguide input light output light
Hi 第14頁Hi Page 14
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| WO2019205918A1 (en) * | 2018-04-26 | 2019-10-31 | Huawei Technologies Co., Ltd. | Optical splitter including a trident structure |
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| WO2019205918A1 (en) * | 2018-04-26 | 2019-10-31 | Huawei Technologies Co., Ltd. | Optical splitter including a trident structure |
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