Controlled formation of femtosecond laser-induced filaments in water

Controlled formation of femtosecond laser-induced filaments in water was introduced and demonstrated experimentally, based on the transverse spatial phase change in the initial femtosecond laser pulse. Single or multi-filament formations were controlled and organized by switching on and off through a computer-controlled transverse spatial phase mask on a liquid crystal Spatial Light Modulator (SLM). We introduced a pi phase step on SLM, which distributed laser intensity non-uniformly and in certain locations peak intensity exceeded the critical threshold, and filaments were formed in the peaks of the intensity. The setup with controllable phase shift on SLM may have great flexibility and convenience in controls of filament formation.