Non-linear absorption of focused femtosecond laser pulses at 1.3 μm inside silicon: Independence on doping concentration

► Tightly focused femtosecond laser beams at 1.3-μm wavelength are used for local energy deposition inside silicon. ► Non-linear absorption is independent on the doping concentration of the silicon substrates. ► The confinement of the interaction can be maintained for thick samples by compensating for spherical aberration. ► The demonstrated local laser energy deposition opens a way for 3D machining inside semiconductors.