Unlocking the power: how crystal size transforms diamond lasers

High-power lasers with high beam quality are widely used across applications such as advanced manufacturing, space exploration, high-energy physics, and defense. Lasers using crystalline gain media have advanced through large-sized crystals, which enable high power outputs by providing large gain volumes and flexible thermal management. However, population-inversion-based lasers remain constrained by energy storage, and the thermal properties of the gain material. Therefore, increasing the size of the gain medium does not fully address severe thermal effects or heat accumulation. As a result, continuous high-power lasing from such lasers with high-beam quality operation is challenging. Nonlinear optical conversion methods have gained attention as a solution, enabling high-power laser emission at wavelengths not directly accessible from gain media. Unlike inversion lasers, lasers based on nonlinear optical conversion avoids energy storage in the medium thus avoiding significant heating. Diamond, with its exceptional optical and thermal properties, including ultra-high Raman and Brillouin gains, large Raman frequency shift, and the highest thermal conductivity among crystalline materials, is a promising nonlinear gain medium. Millimeter-scale diamond crystals have been employed as nonlinear gain media to achieve laser output with peak power reaching megawatt level and continuous-wave power reaching kilowatt level, all while maintaining near-diffraction-limited beam quality. As diamond growth technologies mature, large high-quality diamonds for lasing are increasingly available. This perspective summarizes recent research progress on high-power diamond lasers and analyzes factors such as diamond size and quality that have limited their power scaling. It is anticipated that diamond-based lasers will open new frontiers in high-power laser technologies. In the near future, peak power at gigawatt level and continuous-wave power in the hundreds of kilowatts range are achievable utilizing only centimeter-scale diamond crystals.