Range Of Pulse Shapes Research Articles

Reconfigurable Optical Pulse Generator Employing a Fourier-Domain Programmable Optical Processor

This paper demonstrates a reconfigurable optical pulse generator based on the creation of a high-quality flat continuum that covers the C-band, followed by the tailoring of the spectral amplitude and phase of the continuum using a commercially available reconfigurable programmable optical processor in order to provide an arbitrary picosecond pulse shape or width. The highly efficient continuum is achieved by seeding a highly nonlinear fiber with transform-limited 4 ps parabolic-shaped pulses. A 20 nm 3 dB continuum at the very high repetition rate of 40 GHz is generated. Fourier-domain pulse shaping techniques are then applied to this continuum via the programmable optical processor to generate any arbitrary pulse shape. We present two specific pulse shaping examples suitable for a variety of high-bit-rate applications. The first example shows the improvement in pulse quality using tailored compression techniques over conventional methods and the second example presents multiwavelength pulse generation, which demonstrates the flexibility and range of pulse shapes that can be achieved using this system. Experimental findings are supported with theoretical results.

Heavy-ion fusion targets with «diffuse» spherical radiation converter

Spherically symmetric targets for indirect-drive heavy-ion fusion are studied, in which the fusion capsule is enclosed in a low-density thick spherical shell, where the ion beams are stopped and their energy is converted into thermal radiation. The thermal radiation then drives the implosion of the fusion capsule, with mininum hydrodynamic coupling between the energy deposition region and the ablation layer. The conditions for effectivehydrodynamic decoupling have been derived. It is found that with the use of heavy ions with energy about or below 8 GeV, the beam-to-fuel energy coupling efficiency can be as large as in foreseen conventional hohlraums. On the other hand, these targets only allow for a low dynamic range of pulse shaping, which results in rather poor entropy shaping and modest fuel gain.Robust targets have been designed, which achieve energy gainG≈30, when driven by shaped pulses of 12.5 MJ of 8.5 GeV Bi ions. Inclusion of a high-density pusher, which increases the fuel compression leads to higher gain at lower beam energy, but two-dimensional simulations demonstrate the extremely violent instability of the fuel-pusher interface.