AbstractUltrafast laser pulses (≤1 ps) are qualitatively different in the nature of their interaction with materials, including biotissues, as compared to nanosecond or longer pulses. This can confer pronounced advantages in outcomes for tissue therapy or laser surgery. At the same time, there are distinct limitations of their strong-field mode of interaction. As an alternative, it is shown here that ultrafast laser pulses delivered in a pulse-train burst mode of radiant exposure can access new degrees of control of the interaction process and of the heat left behind in tissues. Using a laser system that delivers 1 ps pulses in 20 μs pulse-train bursts at 133 MHz repetition rates, a range of heat and energy-transfer effects on hard and soft tissue have been studied. The ablation of tooth dentin and enamel under various conditions, to assess the ablation rate and characterize chemical changes that occur, are reported. This is compared to ablation in agar gels, useful live-cell-culture phantom of soft tissues, and presenting different mechanical strength. Study of aspects of the optical science of laser-tissue interaction promises to make qualitative improvements to medical treatments using lasers as cutting and ablative tools.
Strong Field Multiphoton Inversion of a Three-Level System Using Shaped Ultrafast Laser Pulses
