Applications of LED Electro-absorption Modulators with the Photonic Crystal Structure

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.