High-speed on-chip light sources at the nanoscale

Following a similar trend in the scaling of electronic integrated circuits (ICs), the downscaling of optical sources promises revenues such as higher energy efficiency and faster operation speed in photonic ICs. With the rapid development of advanced fabrication techniques and optical cavity designs, light confinement and manipulation at the nanoscale, far below the diffraction limit of light, have been achieved. However, downscaling can lead to problems such as large threshold current and excessive self-heating for nanolasers. In addition, the modulation bandwidth of a laser is ultimately limited by the large damping at high injection current levels due to gain compression. Recently, nanoLEDs that utilize the Purcell effect were proposed as fast and efficient nanoscale light sources to address the limitations of nanolasers. In this review, we summarize recent advances and several important figures of merit of nanoLEDs. To illustrate their practicalities, we use a specific nano-emitter design example to calculate and predict the dynamic response as well as energy consumption of the device with a rate-equation analysis. This short review is intended to offer new perspectives to the design and application of nanoscale light sources in high-speed on-chip optical communication systems.