以光子晶體製作之發光二極體吸光調變器應用

Abstract

近年來，光子晶體在光通訊中占有重要地位，因為其針對在光通訊網路中之訊號路由、訊號開關、訊號濾波…等等課題提供有效的解決方案。再者，因為光子晶體具有控制光流以及對特定波長群速度的抑制能力，故其可提升元件表現，使得在主動元件中使用光子晶體特別具有吸引力。這些行為使得光訊號和主動材料之間的互動更加有效率。藉由將光子晶體與現有元件整合，可以達到更加有效的波長選擇。 在本篇論文中，我們藉由模擬軟體的輔助設計元件。為符合可見光通訊的應用與整合，我們將此元件的中心工作波長設定為450 nm，其與現有的LED晶圓之發光頻譜相符。接著，為驗證模擬結果，我們仔細地選擇元件的晶格常數、缺陷長度、以及缺陷寬度。根據初始元件的量測結果，我們進一步減少元件的可變參數並以此設計可施加電場於其上之具有電極的主動元件。為達成更佳的波長選擇效果，我們將-5V的逆向偏壓於元件上。 在接下來的第二部分實驗中，我們改變不同的入射光源以觀察較長所展現的波長選擇。更進一步，藉由施加順向偏壓於元件上，我們嘗試增加信道(channel)高峰（局部極大）的強度並且抑制相鄰低谷（局部極小）的強度，以獲得更佳的元件表現。除了藍光LED光源以外，我們嘗試了綠光、以及紅光LED，並得到藍光LED具有最佳電致吸收表現之結論。

In recent years, photonic crystals (PhCs) play a key role in optical communication since they offer an efficient solution to the problems of signal routing, switching, filtering, etc. within optical networks. Moreover, the use of PhCs in active components is particularly attractive because it enhances the device performance owing to the capability of manipulating the flow of light and to the possibility of reducing the group velocity at certain wavelengths. This behavior allows a more efficient interaction between the optical signal and the active material. By integrating PhC with current devices, more effective wavelength selection can be realized. In this work, we designed our device with the aid of simulation software. For application and integration in visible light communication, we set the central operating wavelength of the device to be 450 nm, corresponding to the emission spectrum of the LED wafer we have. Then, we carefully chose the lattice constant, defect length and defect width of the device in order to confirm the simulation results. According to the measurement results of the primitive devices, we reduced the device parameters and redesigned the active devices with electrodes to apply electric fields on them. For the purpose of realizing better wavelength selection, we applied reversed bias up to -5V on the devices. Next, in the second part of this article, we change different incident light sources to observe wavelength selection in longer wavelengths. Moreover, we attempt to increase the maximum intensity at the peak of channels and reduce the adjacent minimums by applying forward bias on the devices in order to acquire better performance. Besides blue LED light source, we tried green and red LEDs, and come to the conclusion that blue LED has the best electro-absorption performance.