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標題: | 垂直共振腔面射型雷射之模態與速度特性研究 The Mode and Speed Characteristics of Vertical-Cavity Surface-Emitting Laser |
作者: | Ting-Yu Huang 黃亭瑜 |
指導教授: | 吳肇欣(Chao-Hsin Wu) |
關鍵字: | 光通訊,半導體雷射,垂直共振腔面射型雷射,單模,高頻特性, optical communication,semiconductor laser,VCSEL,mode,RF characteristic, |
出版年 : | 2020 |
學位: | 碩士 |
摘要: | 本論文以氧化孔徑侷限垂直共振腔面射型雷射的高速特性為主題,將高速大訊號傳輸作為目標,針對其直流、動態、雜訊做分析。
第一章介紹目前資料中心對短距離的850 nm VCSEL與單模傳輸的高速特性需求背景和研究動機。 第二章討論了VCSEL的下方DBR部分不參雜以降低吸收的磊晶設計,並以水氧化孔徑的製程結構做出光孔徑大小分別為2.3、4.3、6.3、8.3 μm的VCSEL元件;在直流特性上,最小2.3 μm孔徑的元件為單模且臨界電流較大,Iro較小,熱效應影響嚴重;而另外三個為多模元件,隨著孔徑變大,臨界電流、Iro變大,而熱效應變小;小訊號特性上則是2.3 μm和8.3 μm VCSEL的頻寬大小受外部寄生效應影響較大,隨著孔徑越小,f_R速度增加越快,但小孔徑受限於Iro較小,因此最小2.3 μm孔徑的元件f_R速度無法超過4.3 μm孔徑的元件;儘管孔徑越大,阻尼影響越小,但也因為電流密度較小與多模態同時消耗載子,使f_R速度無法快速增加,無法達到最大頻寬,因此最後選出了4.3 μm孔徑的元件作大訊號傳輸,達到最高速為54 Gb/s。 第三章以單模VCSEL為主題,由於孔徑較小且單模特性,散射損耗和較大的熱效應造成的吸收使臨界電流大於多模小孔徑VCSEL臨界電流。在直流特性上因其熱效應與單一模態的影響,空間燒孔現象嚴重,在大約6 mA隨即roll-over,出光光強受到限制;在動態特性方面,頻率響應在元件外加電流為3.6 mA時即達到飽和,RIN方面則顯示出單模雷射沒有多模雷射的模態競爭效應,因此雜訊較小,對遠距離傳輸有幫助;在遠距離傳輸的部分,此元件可以達到最遠為500 m時傳輸速度為40 Gb/s。 第四章利用Al2O3鈍化改善單模VCSEL特性,解決小元件漏流的問題。在直流特性上降低臨界電流,在頻譜上可達到6 mA並出現了在高電流下允許的第二個模態;在小訊號參數上提升了RP並減小CP,證明此結構可以避免漏流同時提升外部寄生頻寬;在大訊號特性上則提升了4 Gb/s,因此可以說Al2O3鈍化確實改善了小孔徑單模元件的特性。 The main theme of this thesis is high speed characteristic of oxide-confined vertical cavity surface emitting laser. In this thesis, we analysed the DC, dynamic and noise characteristic and tried to make the device achieve high speed eye diagram transmission. In first chapter, we mentioned research background and motivation to the demand of high speed 850 nm VCSEL and single mode transmission. In second chapter, we discussed the epitaxy undoped part of bottom DBR to reduce optical absorption, and made oxide-confined VCSELs with optical aperture size 2.3, 4.3, 6.3, 8.3 μm. The DC characteristics show the 2.3-μm device is single mode with larger Ith and smaller Iro, and the others are multimode device with larger Ith and Iro as aperture size increasing. The small signal characteristics show bandwidth of the 2.3 and 8.3-μm devices are affected by parasitic. As the aperture size decreases, f_R increases rapidly. However, due to the smaller Iro of 2.3-μm device, the fastest f_R of 2.3-μm device doesn’t exceed 4.3-μm device. Although the larger aperture size with smaller damping effect, the smaller current density and modes scrambling for carrier slow the f_R increasing rate, which result in limited bandwidth. So, we selected the 4.3 μm aperture size device and achieve the eye diagram transmission up to 54 Gb/s. In third chapter, we focus on single-mode VCSEL. Because of the smaller aperture size and single-mode characteristic, optical scattering loss and the thermal effect result in the lager Ith. The DC characteristic shows the severe spatial hole burning and thermal effect causing the roll-over at 6 mA, which limited the optical power. The dynamic characteristics show the frequency response saturates at 3.6 mA and the lower RIN comparing multimode devices. The longest transmission distance is 500 m, and the speed up to 40 Gb/s. The fourth chapter is about using Al2O3 passivation to improve the high speed characteristic. This method decreases the Ith ,increases RP and further decreases CP, which obviously fix the leakage problem. It increases 4 Gb/s of the eye diagram transmission and achieve 48 Gb/s. Key words: optical communication, semiconductor laser, VCSEL, mode, RF characteristic |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/62238 |
DOI: | 10.6342/NTU202000944 |
全文授權: | 有償授權 |
顯示於系所單位: | 光電工程學研究所 |
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