The effect of two-photon absorption on the dynamic range of integrated microwave photonics links

Abstract

Recently, Integrated Microwave Photonics (IMWP) on Silicon-on-Insulator (SOI) platform has attracted much attention. SOI as a platform for passive devices has been studied for operation at a wavelength of 1.55 μm. It has been acknowledged that Si suffers from Two-Photon Absorption (TPA) at this wavelength, which potentially limits the dynamic range of microwave photonic links. The TPA effect diminishes at longer wavelengths, and completely vanishes at a wavelength of 2.2 μm. So far, the detailed effects of TPA on the performance of the SOI platform in the context of IMWP have not been well-explored. In this work, a systemic simulation has been performed in order to investigate the effects of nonlinear TPA on the performance of SOI microwave photonic links at 1.55 μm, particularly the dynamic range of the system was studied in-depth. Furthermore, system performance at wavelengths from 1.55 to 2.2 μm was investigated by scaling the device design, where the parasitic effects of TPA are avoided. Based on theoretical analysis, the result showing microwave photonic links at 2.2 μm outperform that at 1.55 μm was obtained as expected. Strip and rib waveguides at 1.55 μm show P1dB points of 3.75 mW and 69.54 mW, respectively, and at 2.2 μm, these waveguides performed linearly throughout the simulated range (up to 1 W of input power) which is due to the dramatically reduced TPA effect. It is noted that the wavelengths at which SOI avoids parasitic TPA match well with the working wavelengths of emerging GeSn lasers and photodetectors.