32-Gbps single silicon microring resonator-loaded Mach-Zehnder modulator

Design and high-speed modulation of a compact and low-voltage silicon microring resonator-loaded Mach-Zehnder modulator (Si MRR-MZM) with a lateral P-N junction are discussed. The driving voltage or the size of a Si MZM is expected to be significantly reduced owing to an enhanced phase shift in an MRR. Modulation characteristics of the MRR-MZM are analyzed on the basis of different device parameters, such as the coupling efficiency K and round-trip length of an MRR. Si MRR-MZMs with different device parameters are fabricated using a complementary metal-oxide-semiconductor (CMOS)-compatible process and their high-speed modulation characteristics are compared. A half-wave voltage of 3.4 V is demonstrated in an MRR-MZM with K = 0.12 and a round-trip length of 128 mu m, and the product of the half-wave voltage and the length of a phase shifter (V pi L)was decreased to 0.036 V cm. The 3 dB bandwidth of an MRR-MZM with K = 0.21 and a round-trip length of 180 mu m is measured to be approximately 16 GHz, and nonretum-to-zero (NRZ) modulation up to 32 Gbps is successfully demonstrated for an operation voltage of 4.0 V. (C) 2018 The Japan Society of Applied Physics