High Power Laser : R & D Activity

The Nd:Glass (Phosphate) High Power Laser design is based on the Master Oscillator Power Amplifier (MOPA) architecture. The laser has two master oscillators. One of them is a Q switched Nd: YLF oscillator giving a pulse of 15 ns (FWHM). The pulse from this oscillator is sliced by a electro-optic pulse slicer to a pulse duration of 3-5 ns. The other oscillator (EXPLA SL 321) is a Stimulated - Brillouin Scattering (SBS) pulse compressed oscillator working with variable pulse duration of 650 ps to 2.5 ns. The pulse from any one of these oscillators is then amplified in three preamplifiers and nine amplifiers varying in diameter from 10 mm to 80 mm.

The schematic of the laser shows all the components. It has 3 preamplifiers followed by six main amplifiers in a single beam line chain. The last amplifier of this chain is a rod amplifier with diameter of 65 mm. The laser out-put of this chain is then split into two arms using beam splitting optics. Each arm has 3-rod amplifiers. The diameter of the last rod amplifier is 80 mm. The laser is a sequentially relayed and spatially filtered to control the beam degradation due to diffraction and self-focusing effects. There are four Faraday isolators in the chain which do not allow the SBS back reflected coherent radiation from the plasma to propagate in the backward direction in the laser chain. The laser chain can be operated to a maximum energy of 100 J in 1 ns pulse duration.

The laser system has been recently upgraded by adding a disk amplifier for amplifying the beam in one arm and a SHG cell to convert the other arm to its second harmonic.

The laser system is being used for studies of thermal x-ray generation in hohlraum cavities and equation of state studies of materials.