F. P. Schäfer

Simplified laser system for the generation of 60 fs pulses at 248 nm

Abstract A simplified hybrid excimer-dye laser system is described, capable of generating subpicosecond pulses at most of the excimer laser wavelengths. In this paper ≈ 60 fs pulse generation is reported at 248 nm, using the above system and additional pulse compression. The effect of the operational conditions of different parts of the system and of the compressor on the spectral and temporal characteristics of the output pulse is studied.

Hybrid dye-excimer laser system for the generation of 80 fs, 900 GW pulses at 248 nm.

Abstract We report the generation of 80 fs pulses at 248 nm using a hybrid dye-excimer laser system. These pulses are amplified in a wide-aperture amplifier to 900 GW peak power.

High-order harmonic generation in carbon vapor and low charged plasma

Abstract Propagation effects in the high-order harmonic generation of high-intensity subpicosecond KrF laser radiation (6 × 10 15 W/cm 2 ) in carbon vapor and low charged carbon plasma are studied. An anomalous behaviour of the fifth harmonic is observed. The continuous growth of its intensity with the plasma length is explained by defocusing of laser radiation and noncollinear phase-matched difference-frequency mixing.

ABSORPTION OF SUBPICOSECOND ULTRAVIOLET-LASER PULSES IN HIGH-DENSITY PLASMA

The absorption of 250 fs KrF laser pulses incident on solid targets of aluminum, copper and gold has been measured for normal incidence as a function of laser intensity in the range of 1012–1014 W cm−2 and as a function of polarization and angle of incidence for the intensity range of 1014−2.5×1015 W cm−2. As the intensity increases from 1012 W cm−2 the reflectivity at normal incidence changes from the low-intensity mirror reflectivity value to values in the range of 0.5–0.61 at 1014 W cm−2. For this intensity maximum absorption of 63–80% has been observed for p-polarized radiation at angles of incidence in the range of 54°–57°, increasing with atomic number. The results are compared with the expected Fresnel reflectivity from a sharp vacuum-plasma interface with the refractive index given by the Drude model and also to numerical calculations of reflectivity for various scale length density profiles. Qualitative agreement is found with the Fresnel/Drude model and quantitative agreement is noticed with the numerical calculations of absorption on a steep density profile with normalized collision frequencies, v/ω, in the range of 0.13–0.15 at critical density and normalized density gradient scale lengths, L/λ0, in the range of 0.018–0.053 for a laser intensity of 1014 W cm−2.At 2.5×1015 W cm−2 a small amount of preplasma is present and maximum absorption of 64–76% has been observed for p-polarized radiation at angles of incidence in the range of 45°–50°.

On some properties of axicons

The radial and axial pump power distribution in the line focus of a cone (as simplest example of an axicon) is discussed. It is also shown that four conical surfaces covered with antireflection coatings can make an efficient polarizer for radial and tangential polarization of a light beam. Glass cones can be used as efficient pump optics for laser-pumped lasers. The advantages of the novel pumping scheme are discussed in detail for the cases of dye-laser and x-ray laser pumping.

Subpicosecond, widely tunable distributed feedback dye laser

A simple, achromatic, widely tunable distributed feedback dye laser arrangement is described. It makes use of a microscope objective, which images a transmission grating into the active medium. With this arrangement subpicosecond operation and broad tunability (400–760 nm) is reported.

Simple generation of high-power, picosecond, tunable excimer laser pulses

Abstract A single excimer laser (a modified commercial oscillation-amplifier combination) is used to pump a dye laser generating a single ps pulse at twice the excimer wavelength and to amplify the frequency-doubled pulse to high peak powers. With XeCl at 308 nm an output pulse energy of 10 mJ with

New laser dyes

A list of 73 new laser dyes is given. These dyes were found in screening fluorescent dyes from a dye collection using a powerful nitrogen laser of 1 MW peak power and 2.5 nsec pulse width.

Comparative study of the gain dynamics of XeCl and KrF with subpicosecond resolution

We have studied the subpicosecond gain dynamics of XeCl and KrF with the following results for XeCl (KrF): saturation energy density 0.85 (2.0) mJ/cm2, small-signal-gain coefficient 0.12–0.15 (0.20–0.22) cm−1, gain recovery of 62% (25%) with a time constant of 52 (54) psec. A molecular reorientation time of ≈1 psec was observed in both excimers.

The phenoxazones: A new class of laser dyes

Abstract A promising new class of laser dyes for the red and near infrared with extended tuning range and high photo-chemical stability is described. Results are given for nitrogen laser pumping, long-pulse flashlamp pumping and cw- operation of one of these dyes.