Laser-Matter Interaction Confined Inside the Bulk of a Transparent Solid

In this chapter we discuss the laser-matter interaction physics that occurs when an intense laser beam is tightly focused inside a transparent dielectric such that the interaction zone where high energy density is deposited is confined inside a cold and dense solid. Material modifications produced in this manner can form detectable nanoscale structures as the basis for a memory bit. We describe the single-pulse-laser-solid interaction in two limiting cases. In the low-intensity case the deposited energy density is well below the damage threshold but it is sufficient to trigger a particular phase transition that in some conditions may become irreversible. At high energy density, the material is ionized early in the pulse, all bonds are broken, the material is converted into hot and dense plasma, and the pressure in the interaction zone may be much greater than the strength of the surrounding solid. The restricted material expansion after the end of the pulse, shock wave propagation, the compression of the cold solid, and the formation of a void inside the target, are all described. The theoretical approach is extended to the case where multiple pulses irradiate the same volume in the solid. We discuss the properties of the laser-affected material and the possibility of detecting it using a probe beam. We compare the results with experiments and draw conclusions.