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首頁> 外文學位 >Design, fabrication, and characterization of novel microcavities for silicon-based light emitters.
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Design, fabrication, and characterization of novel microcavities for silicon-based light emitters.

機譯：硅基發(fā)光體的新型微腔的設計，制造和表征。

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The basic challenge in developing a Si-based light source is overcoming the emission inefficiency of crystalline Si due to its indirect band structure. Numerous efforts have led to an array of Si-compatible materials from which efficient light emission was attained; these materials include Si nanocrystals (Si-ncs), Er doped SiO2 (Er:SiO2), and strained Ge on Si. Based on two of the most promising Si-compatible light emitting materials, Si-nc and Er:SiO2, we designed novel microcavities with the potential to be used in laser designs. We developed fabrication processes for both Si-nc and Er:SiO2 materials and performed extensive material characterization to attain the parameters governing their behavior in the ADE-FDTD model. The cavities designed, fabricated, and characterized in this work consisted of an in-plane corner-cut square microcavity, microdisks and microtoroids, and a concentric microdisk structure designed for a two-stage, CMOS-compatible Si laser.;The waveguide-coupled corner-cut square cavity was fabricated in-plane using E-beam lithography and selective dry etching. Both the lithography and etch processes were optimized to achieve smooth and vertical cavity sidewalls. We experimentally characterized this structure using lensed tapered fibers and saw excellent agreement with the simulated predictions. We identified an optimum corner-cut length which improved the Q-factor for a square cavity by as much as 2x.;We then focused on developing light emitting devices using the Si-nc and Er:SiO2 materials. While neither of these materials on their own satisfies all the requirements for an electrically pumped, CMOS-compatible laser at telecommunication wavelength, we proposed a concentric microdisk design which leverages the advantages of both materials. In the proposed structure, EL from an inner Si-nc microdisk acts as an optical pump for an Er:SiO 2 laser in the outer microdisk. Using our modeling tools, we confirmed the proposed device behavior and optimized the geometry.;To demonstrate the feasibility of this device, we fabricated a series of preliminary light emitting structures, including Si-nc microdisks, Er:SiO 2 microdisks and --toroids, and Si-nc/Er:SiO2 concentric microdisks. We developed two experimental characterization techniques to analyze the whispering-gallery modes (WGMs), one based on free-space collection from the edge of the microdisk and the other based on evanescent coupling to a tapered pulled fiber. The tapered fiber pulling process was refined to allow for in situ monitoring of the transmission and fiber diameter, which drastically improved the reliability and repeatability of this process. We compared these characterization setups and identified the regimes of operation in which each is appropriate. Using these characterization setups, we observed spectrometer limited Q-factors as high as 2x103 for Si-nc microdisks, comparable to the highest Q-factors reported in the literature, and Q-factors as high as 3x106 for Er:SiO2 microtoroids, which are high enough to achieve lasing given an optimized Er concentration. We then developed a fabrication process for the Si-nc/Er:SiO2 concentric microdisks in accordance with our two-stage laser design. Characterization of these concentric microdisks confirmed many of our predictions, including the existence of Si-nc based pump modes and Er:SiO2 based signal modes, the mitigation of free carrier absorption (FCA) loss from the signal modes, and indirect excitation of the Er-based film via Si-nc luminescence. The existence of active and passive modes at both Si-nc based (pump: ∼800 nm) and Er:SiO2 based (signal: ∼1530 nm) wavelengths were in good agreement with the simulated predictions. The FCA loss, which is the dominant loss mechanism in Er doped Si-nc compositions, is almost entirely mitigated in the concentric microdisk structure by spatially separating the pump and signal modes. Having the pump and signal modes spatially separated allowed us to use the Si-nc luminescence as a optical pump for the Er:SiO 2 film. This indirect excitation mechanism was the first demonstration of an integrated two-stage pumping scheme applied to these materials. Finally, we developed a semi-analytical model to predict lasing thresholds in this concentric microdisk structure. Based on this analysis, we identify the material and device optimizations required to achieve lasing in the concentric microdisk structure. (Abstract shortened by UMI.)
機譯：開發(fā)基于硅的光源的基本挑戰(zhàn)是克服結晶硅由于其間接能帶結構而導致的發(fā)射效率低下的問題。大量的努力導致了一系列的硅兼容材料，從中可以獲得有效的發(fā)光。這些材料包括Si納米晶體（Si-ncs），Er摻雜的SiO2（Er：SiO2）和Si上的應變Ge?；趦煞N最有前途的與Si兼容的發(fā)光材料Si-nc和Er：SiO2，我們設計了具有在激光設計中使用潛力的新型微腔。我們開發(fā)了用于Si-nc和Er：SiO2材料的制造工藝，并對材料進行了廣泛的表征，以獲得在ADE-FDTD模型中控制其行為的參數(shù)。在這項工作中設計，制造和表征的腔體包括一個平面內(nèi)切角方形微腔體，微盤和微環(huán)面以及設計用于兩階段，兼容CMOS的Si激光器的同心微盤結構。使用電子束光刻和選擇性干法刻蝕在平面內(nèi)制造角切方腔。光刻和蝕刻工藝均經(jīng)過優(yōu)化，以實現(xiàn)平滑和垂直的腔體側壁。我們使用帶透鏡的漸縮纖維對這種結構進行了實驗表征，并與模擬預測非常吻合。我們確定了最佳的切角長度，將方形腔的Q因子提高了2倍。然后，我們專注于開發(fā)使用Si-nc和Er：SiO2材料的發(fā)光器件。盡管這些材料都不能單獨滿足電信波長電泵CMOS兼容激光器的所有要求，但我們提出了一種同心微盤設計，該設計利用了這兩種材料的優(yōu)勢。在提出的結構中，來自內(nèi)部Si-nc微型磁盤的EL用作外部微型磁盤中Er：SiO 2激光器的光泵。使用我們的建模工具，我們確認了擬議的器件性能并優(yōu)化了幾何形狀。為了證明該器件的可行性，我們制造了一系列初步的發(fā)光結構，包括Si-nc微盤，Er：SiO 2微盤和-環(huán)形和Si-nc / Er：SiO2同心微型磁盤。我們開發(fā)了兩種實驗表征技術來分析耳語畫廊模式（WGM），一種基于微盤邊緣的自由空間收集，另一種基于漸逝耦合至錐形拉制光纖。錐形光纖拉制工藝經(jīng)過改進，可以對傳輸和光纖直徑進行現(xiàn)場監(jiān)控，從而大大提高了該工藝的可靠性和可重復性。我們比較了這些特性設置，并確定了每種合適的工作方式。使用這些表征設置，我們觀察到對于Si-nc微型磁盤，光譜儀限制的Q因子高達2x103，可與文獻中報道的最高Q因子相媲美；對于Er：SiO2環(huán)形微透鏡，其Q因子高達3x106。在優(yōu)化的Er濃度下足夠高以實現(xiàn)激光發(fā)射。然后，根據(jù)我們的兩階段激光設計，我們開發(fā)了Si-nc / Er：SiO2同心微型磁盤的制造工藝。這些同心微盤的表征證實了我們的許多預測，包括基于Si-nc的泵浦模式和基于Er：SiO2的信號模式的存在，減輕信號模式中的自由載流子吸收（FCA）損失以及間接激發(fā)Er Si-nc發(fā)光的鋁基薄膜?；赟i-nc（泵：?800 nm）和基于Er：SiO2（信號：?1530 nm）波長的主動模式和被動模式都與模擬預測非常吻合。 FCA損耗是摻Er的Si-nc成分中的主要損耗機理，通過在空間上分離泵浦和信號模式，在同心微盤結構中幾乎可以完全消除FCA損耗。使泵浦模式和信號模式在空間上分開，使我們能夠?qū)i-nc發(fā)光用作Er：SiO 2膜的光學泵浦。這種間接激勵機制是應用于這些材料的集成兩級泵送方案的首次展示。最后，我們開發(fā)了一個半分析模型來預測這種同心微盤結構中的激光閾值。基于此分析，我們確定在同心微盤結構中實現(xiàn)激光發(fā)射所需的材料和設備優(yōu)化。 （摘要由UMI縮短。）

著錄項

  • 作者

    Marchena, Elton L.;

  • 作者單位

    University of Delaware.;

  • 授予單位 University of Delaware.;
  • 學科 Engineering Electronics and Electrical.;Engineering Materials Science.
  • 學位 Ph.D.
  • 年度 2010
  • 頁碼 215 p.
  • 總頁數(shù) 215
  • 原文格式 PDF
  • 正文語種 eng
  • 中圖分類
  • 關鍵詞

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