Wafer-Scale Fabrication of a Titanium-Sapphire Laser Substrate by Thermal Diffusion

Titanium-doped sapphire (Ti:Sa) finds extensive applications in laser sciences and technologies due to its wide emission bandwidth and relatively large gain cross-section. These characteristics have played a crucial role in the development of lasers with wide tunability, ultrafast femtosecond pulses, and octave-spanning frequency combs. However, the deployment of Ti:Sa lasers in practical applications faces challenges due to their large size, high cost, and the need for significant optical pump power, making miniaturizing these lasers to chip-scale dimensions a paramount goal. In this context, we present a novel wafer-scale Ti:Sa diffusion integration process that serves as an ideal foundation for developing integrated Ti:Sa lasers. We demonstrate uniform broadband emission across the entire wafer. The diffusion depths reach 30 μm, alongside a surface Ti concentration of 0.14 atomic percent. This technique heralds a new era for utilizing diffused Ti:Sa wafers in the development of integrated visible- and near-infrared laser sources.