Dynamics of fs laser modification in glass
We have designed a unique pump-probe experiment (Fig. 1) to study the short timescale dynamics of fs-laser modification by monitoring the plasma that is generated inside the glass during and immediately following the absorption of the incident fs-laser pulse. The interaction of light with a plasma is governed by the properties of the plasma. By comparing the theoretical transmission characteristics of a plasma (Fig. 2) to the experimentally measured transmission of a broadband probe (Fig. 3) it is possible to gain information about the density of the plasma created. In addition, the temporal evolution of this plasma can be studied by measuring the transmission of the probe pulse at different times after the absorption of the modifying fs pump pulse.
Fig. 1. Schematic diagram of fs pump-probe setup
Fig. 2. Calculated spectral transmission of a plasma with a uniform density of 2.5×1020 cm-3 (red), 1.0×1021 cm-3 (blue), and 4.0×1021cm-3 (green).
Fig. 3. Measured transmission spectrum of a broadband probe passing through a plasma created in fused silica using a 6.0 μJ, 180 fs laser pump pulse.