We show first deep UV ablation results achieved with our new all solid state laser system. The system parameters allow high repetition rate ablation with a small spot diameter of about 0.250mm and a fluence of 350 mJ/cm<sup>2</sup> at a wavelength of 210 nm using sequential frequency conversion of a diode pumped laser source. The single shot and multishot ablation rates as well as the ablation profiles have been defined using MicroProf (Fries Research and Technology GmbH, Germany). By means of computer controlled scanning we produce smooth ablation profiles corresponding to a correction of myopia, hyperopia or astigmatism. Due to the small spot size and high repetition rate of the laser we are able to generate in short time intervals complicated ablation profiles described by higher order polynomial functions which are required for the needs of customized corneal ablation.
We report what is to our knowledge the first generation of femtosecond VUV radiation tunable in the spectral range from 102 - 124 nm generated by two photon-photon resonant and near resonant four-wave difference-frequency mixing ((omega) <SUB>DF</SUB> equals 2(omega) <SUB>P</SUB> - (omega) <SUB>1</SUB>) in krypton and argon. The FWDFM process was pumped by intense 250 fs, 193 nm pulses ((omega) <SUB>P</SUB>) derived from the 80 fs output pulses of a 0.1 TW Ti:sapphire laser system by cascaded fourth harmonic generation in three BBO crystals and subsequent amplification in an ArF gain module. The synchronized injection pulses ((omega) <SUB>1</SUB>) were generated in an travelling wave optical parametric system driven by the second harmonic of the Ti:sapphire output. Frequency up-conversion of the pulses at (omega) <SUB>1</SUB> allows the extension of the tuning range also to lower frequencies at (omega) <SUB>D</SUB>.
We report what is to our knowledge the first generation of femtosecond light pulses in the wavelength range from 172.7 to 187 nm in an all- solid-state system operating at kilohertz repetition rate. Phase-matched sum frequency mixing in lithium triborate (LBO) between the fourth harmonic of a femtosecond Ti:sapphire regenerative amplifier and the idler pulses from a traveling wave optical parametric generator pumped by the same amplifier is used to approach these unprecedented short UV wavelengths. Estimations of the achieved pulse duration yield values below 200 fs in the whole vacuum UV tuning range. At 180 nm we measure single pulse energies as high as 50 nJ.
Compact all-solid state laser sources are developed for femtosecond pulse generation tunable around 193 nm utilizing high peak power Ti:sapphire oscillator/amplifier systems and phase matched sequential sum frequency conversion in three (beta) -barium-borate (BBO) crystals arranged in different schemes. Using thin crystals and a delay line for optimization of the temporal overlap of the interacting pulses in the last conversion stage 190 fs optical pulses with pulse energies of more than 2 (mu) J at 193 nm at 20 Hz repetition rate and 170 fs pulses with pulse energies of up to 4 (mu) J at 200 nm (0.8 (mu) J at 193 nm) for 1 kHz repetition rate are produced with excellent spectral, temporal, and spatial stability.