| 摘要: | 現今資訊時代的快速爆炸發展，資訊的傳輸量越趨龐大，並因世界網路
的發展，國與國之間的訊息交換也越趨重要，大量的光纖海底電纜陸續被建
造，而鈮酸鋰晶體憑藉其優異的晶體光學性質，且與電訊號傳輸相比，較難
被竊取與竄改且所需之驅動能源也較低，符合世界的能源降低趨勢，被大量
的被應用在其中，而隨著光通訊時代的來臨，各國無不重視光通訊的發展。
快速電光調製器，為光通訊產業中不可或缺的一項元件，其藉由鈦波導
擴散製程的優勢，具有低的傳播損耗，高的位元率、高發展應用性，以及低
驅動電壓與低訊噪比、低環境溫度影響的優勢，逐漸在美洲、歐洲、日
本……等之本島或跨國的光纖網路、海底電纜的相關設備中被採用。而我國
也透過產學合作的方式與各單位進行相關的研究與發展，以其可以開發出相
關商品，並完成國家自主研究之目標，並期望國家跟上世界各國光通訊世代
的腳步，完成各種相關的產業升級與發展。
本文製作出使用1550nm 光源之3Gbps 電光快速調製器。我們採用Z 切
(Z-Cut)鈮酸鋰晶體，藉以使用鈮酸鋰晶體極高的電光系數，並依電光效應
原理來達成，馬氏干涉儀波導的設計採用商用軟體R-Soft 來輔助完成，波
導製作以金屬鈦擴散製程為主，完成設計波導寬度為7μm、間距寬度為60
μm、S-Bend 長度為6000μm 單模傳輸之馬氏干涉儀(Mach-Zehnder)結構。
電極設計使用高頻模擬軟體(High Frequency Structure Simulator,
HFSS)，並以高頻電訊號傳輸中常使用的共平面波導(Co-Planar Waveguide)
電極結構，並以黃金為材料，當作調製器的驅動電極，得到電傳輸訊號頻寬
(S21)達40GHz 以上，電傳輸反射訊號(S11)低於-18dB。緩衝層我們使用傳統
半導體常見的二氧化矽，並以原子蒸鍍設備輔以製作，以期達成我們速度匹
配的條件，並採用1μm 的厚度來搭配調製器的設計。且為了能夠在與速度
匹配達成更佳的條件，我們必須採用厚電極的設計，所以我們也搭配電鍍系
統，並使用對環境較無害的環保型金電鍍液為材料，在環境溫度35℃下，
成功製作電極厚度高達21μm 的厚黃金電極。
最後完成全長為3.4cm，直波導在TM 模態下的傳播損耗為
0.8735dB/cm，而馬氏干涉儀於TM 模態下的傳播損耗為0.9911 dB/cm，厚
金屬電極之特性，在網路分析儀的量測下其電傳輸訊號頻寬(S21)達
21.3GHz、電傳輸反射訊號(S11)皆低於-15dB，光電轉換訊號於眼圖儀的量測
下具有3Gbps 之頻寬響應，而其驅動電壓經量測為6V。;Today the era of the information explosion are rapid development, data
transportation increasingly more large, and because the development of network
of information exchanging between countries are more important, a large
number of undersea fiber transportation system have been built, and lithium
niobate with its excellent optical properties, and compared with telecom
transmission, it’s more difficult to stolen and tampered, with the low driving
energy required it’s in line with the policy of world energy trends and applies in
many regions. With the advent of optical communication era, none of countries
not to attach this regions.
Ultra‐fast electro‐optical modulator for optical communication industry is an
essential element, which is made by the advantages of titanium in:diffused
process, with low propagation loss, high bit rate, highly application, low driving
energy, and low signal to noise ratio, low ambient temperature affect being
adopted in the relevant countries, like Americas, Europe, Japan, etc....... the
island or cross‐border fiber‐optic network in submarine cables. And Taiwan has
also carried out related research and development by way of industry‐university
cooperation, achieved its related products can be developed independently,
keeping up with the world countries, wish to complete a variety upgrading and
development of related industries.
In this thesis using the 1550nm light source to produce a ultra‐fast electrooptic
modulator with 3Gbps bandwidth. We used a Z‐cut lithium niobate crystal,
using its high electro‐optic coefficient, and in accordance with the principles of
electro‐optic effect, Mach‐Zehnder interferometer waveguide is designed by
using commercial software R‐Soft, the type of waveguide was produced with
titanium in:diffused process, to design the waveguide width of 7μm, arm gap
width of 60μm, S‐Bend length of 6000μm single‐mode transported in Mach‐
Zehnder interferometer structure. Electrode design using a commercial software
“High Frequency Structure Simulator, HFSS” and layout the coplanar waveguide
electrode structure which suit on high‐frequency electrical signal transmission,
driving electrode of modulator was made by gold achieved the bandwidth(S21)
of electrical transmission to 40GHz or more, the reflection signal (S11) of
electrical transmission and less than ‐18dB. We use silicon dioxide as
conventional buffer layer on semiconductor industry with atomic vapor
deposition equipment, in order to reach our velocity matching conditions and
thickness of buffer layer is 1μm to suit the modulator design. And we try to reach
a better velocity matching conditions, we must use thicker electrodes structure,
so we developed the electroplating systems, using eco‐friendly gold plating
solution as material, successfully fabricated thickness of electrode up to 21μm
at ambient temperature at 35 ℃
Finally we achieved the total length of 3.4cm, the propagation loss of
straight waveguide under TM mode transmission is 0.8735dB / cm, while Mach‐
Zehnder interferometer propagation loss is 0.9911 dB / cm under TM mode, we
use Network Analyzer to measure the S‐parameter which bandwidth(S21) up to
21.3GHz and reflection(S21) signal are lower than ‐15dB, and achieved the
frequency response of 3Gbps bandwidth under driving voltage is 6V with the Eye‐
Diagram. |
