我們設計一個高效率－頻寬乘積(EBP)的PIN鍺光偵測器，並將光纖耦合進環形共振腔的“臨界耦合”現象，運用在元件上，使所有入射光能量被鎖進共振腔中，大幅提高鍺的吸收效率，使得只需數百奈米厚度的鍺，就可以達到90%的量子效率，傳統上PIN鍺光偵測器，則需要數微米，並且因為厚度很薄，載子傳輸時間短，頻寬可以高達50GHz，但缺點是線寬只有 ，為了改善線寬太窄，容易受波長漂移影響而降低量子效率，我們運用了反色散關係鏡子，利用其特殊的反射相位趨勢，補償了因雷射不穩，導致波長偏離造成的相位損失，進一步達到平頂陡邊的高量子效率頻譜。

We design a High efficiency-bandwidth product(EBP) PIN Germanium photodector and use critical coupling theory to analysis our structure . It can lock all incident light in this photodector so significantly enhance Quantum efficiency result in only several hundreds of nanometer thickness but Quantum efficiency can exceed 90%.Because of a very thin depletion region, carrier spend a few transit time , and bandwidth can exceed 50GHz . Some disadvantage like linewidth is too narrow so if light source wavelength shift let Quantum efficiency drop significantly , To overcome this problem , we use anomalous dispersion mirror to compensate cavity total phase and realize flat-top Quantum efficiency.

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