“…In addition, several sophisticated and unique structures have also been proposed, such as an EAM with a strained asymmetric quantum well absorption layer for small-chirp operation, 14) a Mach-Zehnder interferometer-type EAM for very-low-voltage operation, 15) and a lateral p-i-n structure EAM for high-speed modulation. 16) On the other hand, multimode interference (MMI) devices 17,18) are widely applied to photonic integrated circuits as passive couplers, [19][20][21][22][23][24][25][26][27] LDs, 28) photonic switches, [29][30][31][32][33][34] tunable couplers, 35,36) signal processing, 37,38) and polarization beam splitters. 39,40) Novel optical modulators based on MMIs have also been proposed.…”