Local Tuning of the Epsilon‐Near‐Zero Condition in Hybrid Silicon Waveguides Using Reactive Laser Annealing

The ability for locally tuning devices in photonic integrated circuits could be an essential function for a wide range of applications requiring reconfigurable photonics. This work demonstrates the application of postgrowth reactive laser annealing to selectively tune the optical properties of tin‐doped indium oxide (ITO) patches integrated in silicon waveguides. ITO stands out due to its distinctive ability to operate in the epsilon‐near‐zero (ENZ) regime at near‐infrared wavelengths. The precise local tuning of the ENZ wavelength in ITO/Si hybrid waveguides by controlling the laser annealing fluence is demonstrated. This technique uniquely allows for the customization of optical constants at critical telecom wavelengths. The findings present a powerful and adaptable method to exploit the exceptional qualities of ITO and, by extension, other transparent conducting oxides, paving the way for the functional diversification of hybrid photonic devices on a singular‐silicon chip.