Highly Compact and Efficient Four-Mode Multiplexer Based on Pixelated Waveguides

An ultra-compact mode multiplexer for TE0, TE1, TE2and TE3modes is proposed and demonstrated experimentally. The device is realized via pixelated waveguides with a footprint of only 5.4 × 6μ m2. The measured insertion loss of the multiplexer is less than 1.5 dB. The inter-mode crosstalk is ~ -20 dB at 1550 nm and below -14.6 dB from 1510 nm - 1570 nm. The fabrication and temperature tolerance of the device are investigated. The device can well tolerate the nanohole diameter variation of ±10 nm and the temperature variation of 100 K. The compactness of the proposed mode multiplexer enables potential applications in densely integrated multimode photonic circuits.