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標題: | 表面聲波調變可見光通訊之研究 Surface Acoustic Wave Modulated Visible Light Communication |
作者: | Meng-Yu Tsai 蔡孟諭 |
指導教授: | 黃建璋(Jian-Jang Huang) |
關鍵字: | 發光二極體,可見光通訊,表面聲波,頻率響應,光學振盪, light-emitting diode,visible light communication,surface acoustic wave,frequency response,optical oscillation, |
出版年 : | 2020 |
學位: | 碩士 |
摘要: | 隨著光通訊系統的興起,如今已廣泛運用在我們的日常生活中,透過傳統照明與無線通訊的應用,使得可見光通訊的技術越來越重要,在無線電的領域裡扮演重要的角色,尤其可以大量應用在室內定位或車間通訊等。近年來無線通訊的需求大量提升,增加元件的操作速率一直都是重要的議題。如今最主要的照明來源以藍光發光二極體為主,但常常受限於較長的自發性輻射複合生命週期,使得調變頻寬不甚理想,因此在以照明功能為基礎的前提下,提升元件操作速率是本論文的主要目標。 近年來三五族的材料非常熱門,尤其是具有壓電特性的相關半導體,這吸引更多人參與表面聲波的研究,應用在軍事、無線通訊等相關領域,而以表面聲波進行聲光調製的機制同樣也被廣泛研究。本論文嘗試利用交叉指狀電極產生表面聲波,以此來提升垂直式發光二極體的特性,當二極體受到110 MHz的表面聲波影響下,聲電流透過聲波的位能傳遞,可以提升二極體約2.5%的輸出光強度。而表面聲波的共振頻率會由二極體的腔體結構所決定,透過適當的表面聲波頻率輸入至發光二極體中,會使之產生990 MHz的光學振盪。 另外,表面聲波對於二極體發光強度的影響亦是值得探討的一大重點。當聲波於壓電材料上傳遞時,其伴隨的位能會造成晶格振盪,於位能的最小值處捕獲載子並帶往主動區,但同時聲波位能亦會使得量子井的結構更加傾斜,造成波函數的空間分離。本文中利用不同頻率的表面聲波可以觀察到發光二極體的不同光輸出,這取決於上述所提到的物理機制。而隨著外加於二極體的電壓提升,電場強度的增加使得量子井的能帶更加傾斜,額外的熱能也影響表面聲波的傳輸特性,進而影響發光二極體的光學響應。了解聲波的作用機制後,不僅可以於常溫下達到超過1 GHz的光學振盪,更可以透過外加偏壓的改變實現可調式光學頻率響應裝置。 The visible light communication (VLC) system has been widely used in our daily life. For wireless communication, the potential of the VLC system has shown as a choice of radio source attribute to the ability to integrate with the lighting infrastructure. As the demand for data content has increased significantly in recent years, improving the bandwidth of components has been an important topic. The blue-light light-emitting diode luminaires have gradually replaced traditional bulbs as the main lighting source today. However, it is often limited by the long spontaneous radiation compound life cycle, which makes the frequency modulation bandwidth undesirable. Therefore, under the premise of lighting function as the basis, improving the operating speed of the components is the main goal of this thesis. In recent years, the materials of III-V semiconductors are very popular, especially related to piezoelectric characteristics. More people are attracted to participate in the research of surface acoustic waves (SAWs), which are used in military, wireless communications, and other related fields. The mechanism of acousto-optic modulation using surface acoustic waves has also been extensively studied. This thesis attempts to use an interdigital transducer (IDT) to improve the characteristics of the vertical light-emitting diode (VLED). When the diode is induced by the SAW at 110 MHz, an acoustic current will be generated, which increases the diode light output by 2.5 %. The resonance frequency of the SAW will be determined by the cavity structure of the VLED. A 990 MHz optical oscillation can be induced by inputting the appropriate frequency of SAW. Moreover, the effect of SAWs on the light output of the LEDs is also a major focus worth discussing. When the SAW propagates on the piezoelectric material, the accompanying potential will trap carriers at the potential minimum and drag them towards the active region. However, the potential of SAW will also make the structure of quantum wells tilt and cause the spatial separation of the wave function. In this thesis, SAW with different frequencies can be used to observed the different light output of LEDs, which depends on the physical mechanism mentioned above. With the increase of the bias voltage, the corresponding increase of optical output leads to the rise of junction temperature. The thermal disturbance intensifies the vibration of lattice, which causes the properties of SAW and the electro-optic frequency response of LED to change. After understanding the mechanism of SAW modulated LED light output, not only can the optical oscillation exceed 1 GHz at room temperature but also the tunable optical frequency response device can be realized by changing the applied bias voltage. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/52764 |
DOI: | 10.6342/NTU202002511 |
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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