Search

Recently, ultrafast lasers have received increased attention in a variety of biomedical applications, including refractive corneal surgery. The laser-tissue interaction with ultrashort laser pulses is based on laser-induced optical breakdown (LIOB), which results in the generation of a microplasma. Due to the expansion of the hot plasma a shock wave and a cavitation bubble are generated. As a result of this process, termed photodisruption, tissue in the focal volume is destroyed. LIOB can be achieved at significantly smaller threshold energies when using femtosecond laser pulses [1]. Furthermore, shock wave and cavitation bubble effects are reduced for the shorter pulses [2], allowing for minimally invasive and well localized corneal surgical procedures.

We present experiments indicating that it is possible to ablate the sclera without damage to the overlaying conjunctiva. A femtosecond Nd:glass laser with 8.5-/spl mu/J pulse energy was used to ablate the top layers of sclera when the laser was delivered through the conjunctiva. In a separate experiment, the same laser was able to create a drainage channel through the whole thickness of the sclera from the outside inward. We created the channel by scanning the laser along spiral patterns at increasing depths into the sclera. Approximately 100 spiral scans were performed, for a total procedure time of 8 min. The diameter of the hole at the outer and inner surfaces was approximately 0.5 mm and 0.15 mm, respectively. Pictures of a side cut show little or no collateral tissue damage.

Femtosecond lasers emitting in the wavelength range around 1 /spl mu/m are attractive sources for a variety of applications. At 1.06 /spl mu/m, neodymium-doped glass offers both the relatively broad gain bandwidth, which is necessary for femtosecond pulse generation, and a strong absorption band around 800 nm, which allows for direct diode-pumping. Femtosecond pulses from diode-pumped Nd:glass lasers were previously reported, using intracavity semiconductor saturable absorber mirrors (SESAMs) to obtain mode-locking. In these lasers prism pairs were used for compensation of intracavity material dispersion and of self-phase modulation, limiting the reliability and compactness of the systems. Towards more compact and reliable femtosecond lasers we demonstrate a SESAM-mode-locked Nd:silicate laser, which uses Gires-Tournois interferometer mirrors for dispersion compensation and which is pumped by only a single laser diode.