Multi-mode optical fiber

Physics

Multiplexing

Power dividers and directional couplers

Cladding (metalworking)

Insertion loss

Optics

Metallurgy

Materials science

Optical fiber

Waveguide

Computer science

Coupled mode theory

Refractive index

Optoelectronics

Telecommunications

Photonics Research

We propose and experimentally demonstrate a novel ultracompact dual-mode waveguide crossing based on subwavelength multimode-interference couplers for a densely integrated on-chip mode-division multiplexing system. By engineering the lateral-cladding material index and manipulating phase profiles of light at the nanoscale using an improved inverse design method, a subwavelength structure could theoretically realize the identical beat length for both TE0 and TE1, which can reduce the scale of the device greatly. The fabricated device occupied a footprint of only 4.8  μm×4.8  μm. The measured insertion losses and crosstalks were less than 0.6 dB and −24  dB from 1530 nm to 1590 nm for both TE0 and TE1 modes, respectively. Furthermore, our scheme could also be expanded to design waveguide crossings that support more modes.

Ultracompact dual-mode waveguide crossing based on subwavelength multimode-interference couplers