Morphology Engineering Enabled Mid‐Infrared Ultra‐Dense Waveguide Array with Low Crosstalk

Abstract

The mid‐infrared (MIR) band holds significant promise in various fields, including thermal imaging, spectroscopy sensing, infrared countermeasures, and free‐space communication, due to its distinctive characteristics. Despite substantial efforts that have been dedicated to building on‐chip photonic integrated circuits for MIR, enabling system miniaturization and broadening application scopes, the challenge of crosstalk among closely packed waveguides persists, hampering improvements in integration density and device performance. Here, a morphology engineering approach is proposed to tailor coupling and suppress crosstalk within a densely arranged waveguide array. These results demonstrate that by introducing a periodic Bezier curve to adorn the waveguide trajectory, coherent coupling can be disrupted, isolating each waveguide and minimizing crosstalk in the array. An experimentally demonstrated eight‐channel waveguide array with a half‐wavelength pitch operating at 3.55 µm exhibits crosstalk suppression exceeding −29 dB, representing an 8 dB improvement compared to a sinusoidal trajectory. This methodology, offering precise control of on‐chip light guiding, coupling, and routing, provides a promising perspective for high‐density design in photonic integrated circuits at MIR.