Optical penetration models for practical prediction of femtosecond laser ablation of dental hard tissue.

Objectives: To develop and practically test high-precision femtosecond laser ablation models for dental hard tissue that are useful for detailed planning of automated laser dental restorative treatment.

Methods: Analytical models are proposed, derived, and demonstrated for practical calculation of ablation rates, ablation efficiency and ablated morphology of human dental enamel and dentin using femtosecond lasers. The models assume an effective optical attenuation coefficient for the irradiated material.

Investigation of laser wavelength effect on the ablation of enamel and dentin using femtosecond laser pulses.

We investigated the effect of femtosecond (fs) laser ablation of enamel and dentin for different pulse wavelengths: infrared (1030 nm), green (515 nm), and ultra-violet (343 nm) and for different pulse separations to determine the optimal irradiation conditions for the precise removal of dental hard tissues with the absence of structural and compositional damage. The ablation rates and efficiencies were established for all three laser wavelengths for both enamel and dentin at room temperature without using any irrigation or cooling system, and the surfaces were assessed with optical and scanning electron microscopy, optical profilometry, and Raman spectroscopy. We demonstrated that 515 nm fs irradiation provides the highest rate and efficiency for ablation, followed by infrared.

Femtosecond laser dentistry for precise and efficient cavity preparation in teeth.

High fluence focused femtosecond laser pulses were used to perform fast, high precision and minimally damaging cavity cutting of teeth at room temperature without using any irrigation or cooling system. The optimal ablation rates were established for both enamel and dentin, and the surfaces were assessed with optical and scanning electron microscopy, Raman spectroscopy and optical profilometry. No chemical change in the composition of enamel and dentin was observed.

Formation of nanochannels in sapphire with ultrashort Bessel pulses.

We explore, both by numerical simulations and experimentally, the flexibility in controlling Bessel beam parameters by re-imaging it into transparent material with a demagnifying collimator for the formation of high-aspect ratio nanochannels. Analysis of nanochannels produced by in-house precision-made axicon with 275 fs pulses in sapphire reveals the intensity threshold of ∼7.2 × 10 W/cm required to create the cylindrical microexplosion.

High-speed multi-jets printing using laser forward transfer: time-resolved study of the ejection dynamics.

This paper extends the current understanding of the laser-induced forward transfer (LIFT) process to the multi-jets ejection problem. LIFT has already been used to print micrometer-sized droplets from a liquid donor substrate with single pulse experiments. Here we study the dynamics of the high-speed multi-jets formation from silver nanoparticles ink films with a time-resolved imaging technique.

Pulsed-laser printing of silver nanoparticles ink: control of morphological properties.

Fine electrically-conductive patterns of silver nanoparticles ink have been laser printed using the laser-induced forward transfer (LIFT) technique. LIFT is a technique that offers the possibility of printing patterns with high spatial resolution from a wide range of materials in solid or liquid state. Influence of drying the ink film, previous to its transfer, on the printed droplet morphology is discussed.