Efficient and broadband dual-mode fiber-to-chip coupler via blazed subwavelength grating

We propose and demonstrate an efficient and broadband silicon-based dual-mode fiber-to-chip coupler implemented with a blazed subwavelength grating structure. The device enables low-loss coupling of TE₀–LP₀₁ and TE₁–LP₁₁ modes while maintaining wide operational bandwidth. Detailed design principles are discussed, with simulations predicting coupling efficiencies of −2.07 dB (LP₀₁) and −2.47 dB (LP₁₁) and 1 dB bandwidths of 55 nm and 57 nm, respectively. Experimental results confirm coupling efficiencies of −3.03 dB (LP₀₁) and −3.75 dB (LP₁₁), with a 1 dB bandwidth exceeding 52 nm over the 1520–1580 nm range. The proposed coupler combines high efficiency and broad bandwidth, offering a compact and fabrication-friendly solution for mode-division multiplexing in high-capacity optical interconnects.