Ultrashort laser pulses are extremely powerful tools for laser-matter interaction, especially suited when applied to transparent dielectrics. They have shown their potential for applications ranging from ultrafast laser-induced optical switches to high-precision laser micro-fabrication. However, efficient use and accurate control of interaction require a deep knowledge of complex phenomena occurring during laser pulse absorption. In this talk, I will present our recent works on ultrashort-pulse energy deposition in fused silica for ablation purposes. Experimental results investigating the efficiency and the dynamics of femtosecond laser pulse absorption shed light on the link between the very first step of interaction (absorption) and the final outcome of material ablation.