R. Volk

The asterix III pulsed high-power iodine laser

A system description and first results of the Asterix III high-power iodine laser built at IPP Garching are given. This laser is designed to yield an output energy of 1 kJ in about 1 ns. Until now pulses with output energies up to 300 J and pulse lengths ranging from 1 to 3 ns have been obtained.

n2-measurements at 1.32 μm of some organic compounds usable as solvents in a saturable absorber for an atomic iodine laser

Abstract We have measured the nonlinear index of refraction n 2 of 12 organic compounds by means of a time integrating interferometric technique using pulses of about 0.7 ns duration from an atomic iodine laser working at 1.32 μm. The accuracy of the n 2 -values obtained is ± 20%. The results may help to facilitate the proper choice of a solvent for a dye usable as a saturable absorber for an atomic iodine laser.

60-J 1-nsec iodine laser

A systems description is given for a two−stage oscillator−amplifier iodine laser setup. Detailed technical data are reported and information is given on the pressure dependence of the oscillator pulse, the gas composition for the oscillator and amplifiers, the small−signal amplification, and the energy storage and energy extraction in the amplifier stages. These performance data demonstrate the suitability of this new laser system for high−energy short−pulse operation.

Iodine laser oscillator in gain switch mode for ns pulses

Abstract An iodine laser oscillator is described, which delivers several mJ in ns-pulses. The oscillator is mode-locked by means of an acoustooptical modulator, the pulse duration varies with the iodine pressure. Apparent self-modelocking is due to saturation effects.

Advanced iodine laser concepts

The essential features of an advanced iodine laser are outlined. These are governed primarily by the proper choice of the stored inversion density of an amplifier and also by the means to enhance the energy extraction efficiency to values in excess of 50 percent. With these measures an amplifier chain with output energies in the kJ range and overall system efficiencies of almost 0.2 percent can be designed. This value is twice as high as that now achieved. As the laser-fusion experiments require a greater pulse duration variability than hitherto obtained, an oscillator pumped by an excimer laser is developed, allowing chain output pulse durations in the range from some 100 ps to several ns. The frequency conversion of iodine laser light by nonlinear interaction in crystals is also investigated.

Stimulated Brillouin back-scattering losses in weakly inhomogeneous laser-produced plasmas

Studies of the reflection from a plane solid target plasma produced with a 1 TW iodine laser ( lambda =1.3 mu m) at pulse durations of 300 ps are presented. The specularly reflected and the back-scattered light were observed separately for a wide range of intensities and with spot sizes of 60 mu m. Stimulated Brillouin scattering was identified as the main mechanism for back-scattering with saturation at 20-30% reflection.

100‐ps pulse generation and amplification in the iodine laser

We have generated 100–200‐ps iodine 1.315‐μ laser pulses by means of the free induction decay (FID) technique. A 2.5‐ns switched‐out pulse from a mode‐locked oscillator is truncated by generating its own gas breakdown in the focal spot between two lenses and then passed through a hot I2 absorber operated in the small‐signal regime to generate a short FID pulse. Streak camera studies of such pulses showed that the breakdown time was about 40 ps and the FID pulses had a full width at half‐maximum of about 100–200 ps. Subsequent amplification of a pulse showed that the 4‐GHz bandwidth of the atmospheric pressure iodine amplifier was insufficient to cover the pulse spectrum. A calculation of the pulse width based on the reduction of the small‐signal gain due to such spectral considerations also gave pulse widths in the 100–200‐ps range.

A tunable iodine laser

The tuning of an atomic iodine photodissociation laser over 11 wavenumbers is reported. The Zeeman effect is used to tune the laser, which is operated in a longitudinal magnetic field of up to 75 kG.

The pulsed high power iodine laser Asterix III

Three-dB couplers or power dividers are expected to be important components in optical waveguide amplitude modulators or switches which operate by interferring two phase-shifted guided waves.’ The conventional 3-dB coupler operates by maintaining a degree of velocity synchronism between two coupled waveguides over a coupling length L. Fabrication tolerances posea difficult problem in construction of such a coupler, since the necessary length L for 50-50 power division between the coupled guides depends on the coupling constant. Also the degree of synchronism must be maintained over the coupling length L. We propose a novel device which allows 50-50 power division between two coupled waveguides with reduced fabrication tolerances. It requires a degree of mode synchronism only at a single point, and the exact length of the coupler is not

Status of the Asterix IV iodine laser

After a description of the design and layout of the 2 kJ/5 TW single beam Asterix IV iodine laser the steps necessary for obtaining a laser beam intensity profile as homogeneous as possible are reported. These steps are: providing a homogeneous inversion density profile in the amplifiers by an appropriate flashlamp-reflector geometry and by compensating the edge enhancement caused by the image relaying system by suitable soft apertures. The paper concludes with a description of the results obtained by the laser system with the end-amplifier not in operation. The full system will become operational at the end of 1990.