Pump-Probe Detection of Diamond Ionization and Ablation Induced by Ultra-Fast Laser

Diamond, widely used in optoelectronic devices, plays a crucial role in improving performance through studies of its electronic structure and optoelectronic response. This study combines computational methods and experiments for analysis. Density functional theory calculates the diamond’s band structure and refractive index, while the Keldysh formula determines the laser intensity at the critical plasma density by evaluating laser-induced free electron density. By integrating the coupled model with a multi-physics field associative assignment, the critical plasma length in the diamond is further simulated. Experimentally, pump-probe techniques examine the diamond’s response under varying pulse widths and energies. Results show that increasing laser energy extends both plasma and damage lengths. As pulse width increases, plasma length first decreases and then increases, while graphitization length shows the opposite trend. Experiments show that laser energy enhancement significantly expands the plasma morphology by enhancing the nonlinear ionization effect. When the pulse width exceeds the electron-lattice relaxation time, the lattice energy deposition triggers localized graphitization, which enhances the subsequent laser absorption, and the final plasma distribution shows a high spatial correlation with the graphitized regions.