Loss Compensation in Microring-Based Si Photonics Devices via Er3+ Doped Claddings

We propose and demonstrate a method to compensate insertion losses in Si photonics devices based on ring resonators fabricated in SOI foundries, with no additional chip area used. It consists in the employment of Er:Al
₂
O
₃
as the upper cladding layer on standard Si/SiO
₂
rings, requiring only one simple post-processing step. The method is modeled in detail, and simulation results for single-ring configurations and photonic molecules are discussed, where the potential for loss reduction is predicted for different design choices based on the quality factor. We experimentally verify the viability of the method, obtaining an output power increase of 1 dB when a single-ring resonator is pumped. This value is increased when the method is applied to devices based on photonic molecules, where a value of 2.6 dB has been measured. This is equivalent to a loss reduction potential higher than 3 dB for a photonic molecule designed to achieve a quality factor of 50000.