光子晶體面射型雷射特性之研究

Abstract

本論文主旨在研究高輸出功率的單一模態光子晶體面射型雷射。因面射型雷射具有圓形輸出光束、低製作成本、單一縱模操作、以及整合二維陣列的潛在特性，因此在光纖通信及中、短距離數據通信上，成為極具潛力的發光源，另外亦可應用在光儲存、光感測、顯示系統上等等。而高功率單模輸出面射型雷射的應用包含了高速雷射列印、光儲存和長波長通訊上的應用。但是要得到單一模態,氧化孔徑必須要小於3um，造成大電阻而侷限了調變頻寬和高速特性，因此製造大面積單一模態的高亮度面射型雷射為此論文的重點。近年來光子晶體已被證明的確具導引與侷限光場的效果，利用晶體這個結構，我們已經成功的應用在長波長的面射型雷射原件上了，包含了850nm、980nm和1300nm等波長面射型雷射。 在850nm的氫離子佈值光子晶體面射型雷射的結構中，光子晶體提供元件光場侷限（即index-guiding），而質子佈植提供電流侷限（即gain-guiding）。此元件的單橫模輸出特性非常優異，其側模壓抑率（side-mode suppression ratio）大於40 dB，且在質子佈植孔徑為10 □m下，其臨界電流只有1.25 mA，而遠場發散角約為6.5o。 在980nm的铟鉮化鎵量子點光子晶體面射型雷射的結構中，造成單一模態輸出。當操作電流為28mA下其最大輸出功率為3.8 mW，而其側模壓抑率（side-mode suppression ratio）大於35 dB而其遠場發散角約為6.8o。 在1300nm的铟化鎵量子點光子晶體面射型雷射的部分，在光纖光學應用上還是首度被研究,我們已經成功的製作出單一模態輸出的面射型雷射，其輸出最大功率為0.2 mW，臨界電流4.75 mA，而其側模壓抑率（side-mode suppression ratio）大於40 dB在所有操作電流下，在未來研究上，此法也可以應用在其他波長上原件的製作。

In this thesis, we have fabricated a high power singlemode photonic crystal vertical-cavity surface-emitting laser (PhC-VCSEL). VCSELs possess circular-output beam, single longitudinal-mode operation, and possible integration of two-dimensional array. Hence, VCSELs are potentially suitable for light sources in fiber communication systems, medium and short distance data transmission systems. Other applications include optical storage, optical sensing, and display systems etc. High-power, singlemode operation is desired for a number of applications, including high-speed laser printing, optical storage and long-wavelength telecommunications. For oxide-confined VCSELs, the current-confined aperture must be less than 3 um in diameter to ensure stable singlemode operation. However, the large resistance inherited from the small aperture limits the modulation bandwidth and degrades the high speed performance. Therefore, it is very important to investigate the larger output aperture of singlemode VCSEL. Recently, a two-dimensional photonic crystal (2D PhC) structure formed on a VCSEL surface as been investigated as a control method of lateral mode. Using the photonic crystal structure, we have successfully applied on the long-wavelength VCSELs, including of 850nm, 980nm and 1300nm VCSEL. In 850nm of the proton-implanted VCSELs with photonic crystal structures, this approach showed single-output transverse mode with high SMSR over 40 dB and ultra-low far-field angle about 6.5o. Moreover, this device also had a ultra-low threshold current about 1.25 mA with proton-implanted aperture of 10 um. In 980nm of InGaAs sub-monolayer (SML) quantum dot VCSELs with photonic crystal structures, single fundamental mode CW output power of 3.8 mW at 28 mA has been achieved, with a threshold current of 0.9mA. Side-mode suppression ratio (SMSR) larger than 35 dB has been demonstrated over entire current operation range and ultra-low divergent angle about 6.8o. In 1300nm of the InAs quantum dot PhC-VCSEL, single fundamental mode CW output power of 0.2 mW has been achieved with a threshold current of 4.75 mA. Side-mode suppression ratio larger than 40 dB has been observed over the entire thermally limited operation range. In the future, this way can be applied on the other wavelength device.