PN junction and RF electrode design for silicon photonics traveling wave mach-zehnder modulator

Abstract

Silicon photonics is a technology platform that can mass-produce optical integrated circuits on silicon wafers. This technology utilizes the existing CMOS-VLSI foundry process infrastructure to simultaneously mass produce at low cost with electronic integrated circuits. Recently, traffic between data centers is expected to explode due to 5G, Big Data, and other connection services. As a solution to this problem, optical transceiver technology having a low power and a wide bandwidth has been attracting attention. The optical modulator is an essential element of an optical transceiver and is being actively developed. In this thesis, we tried to implement a high performance Mach-Zehnder based optical modulator (MZM) was implemented thorough silicon photonics technology and we developed core technology in cooperation with National Nano Fab Center (NNFC).

Through the design of various PN junctions and microwave transmission line, a modulator with wide bandwidth was fabricated and characterized. A PAM-4 modulated silicon photonic Mach-Zehnder optical modulator has the advantage of increased bandwidth, but has a high penalty for signal-to-noise ratio, so it is sensitive to the linearity of the components and thus requires a high extinction ratio. Therefore, a high efficiency multi electrode MZM is realized by PN junctions with vertical depletion and interleaved PN juction operating at 1550 nm. Through three times fabrication of optical integrated circuit, passive and active devices were characterized. A 6 dB extinction ratio and a 45 Ghz 3-dB electro optic bandwidth was measured at 4 V reverse biased. Optical modulators that can be driven under low voltage conditions are advantageous for packaging. A 56 Gbps PAM-4 modulated Silicon MZM at a single wavelength will be an integral part of the 200 Gbps optical interconnect.