Width-modulated Half-Wavelength Pitch Silicon Waveguide Array for Dense Integration

In this work, we propose and demonstrate a compact low-crosstalk silicon waveguide array for dense integration of passive photonic devices. In this device, the waveguide pitch of the array is set to half of the working wavelength. To achieve low crosstalk, the widths of the waveguides in the array are modulated, and the modulation phase difference between adjacent waveguides is set to π. Based on Floquet theory, quasi-energy collapse would occur and a zerocrosstalk transmission can then be achieved. Simulation results show that, for a 104.5-μm-length array, the insertion loss is as low as 0.09 dB and the crosstalk is below −23 dB in 1500 nm - 1580 nm. In the experiments, an insertion loss of 0.6 dB and crosstalk lower than −23 dB are obtained at a wavelength range from 1530 nm to 1570 nm. Our device exhibits the ability to suppress transmission crosstalk while maintaining low propagation loss, revealing its potential in enhancing the integration density of CMOS-compatible passive optical components.