A nonlinear device for ultrafast processing is proposed. This device is based on the nonlinear propagation in a waveguide loop formed by connecting the output ports of a conventional coupler. The device is shown to have potentially useful characteristics for unequal coupling ratios and has the ability to operate on entire pulses when soliton effects are included.

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We examine the propagation of solitons in the two linearly polarized modes of a birefringent fiber. The behavior of single solitons is similar to that of continuous waves, and the nonlinear effects make the fast mode unstable when the beat length between the modes is long. Even with the instability, nondispersive pulses can still propagate. Highorder solitons break up and can transfer most of the energy into a single, highly compressed soliton.

We report on the design and fabrication of fully 2-D surface relief diffraction elements that can split a single collimated beam into many beams in an arbitrary intensity distribution. These splitters were designed by computer using simulated annealing, and made into phase gratings by electron-beam lithography followed by plasma etching into quartz glass. Both two and four phase level gratings have been fabricated, allowing a wide range of uniform and weighted spot patterns to be generated. These grating elements have a measured diffraction efficiency of over 74%, with the beam intensity ratios accurate to within 1% of their target values.

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Encapsulated wire-element stress gauges enable changes in lateral stress during shock loading to be directly monitored. However, there is substantial debate with regards to interpretation of observed changes in stress behind the shock front; a phenomenon attributed both to changes in material strength and shock-dispersion within the gauge-encapsulation. Here, a pair of novel techniques which both modify or remove the embedding medium where such stress gauges are placed within target materials have been used to try and inform this debate. The behavior of three polymeric materials of differing complexity was considered, namely polystyrene, the commercially important resin transfer moulding ͑RTM͒ 6 resin and a commercially available fat ͑lard͒. Comparison to the response of embedded gauges has suggested a possible slight decrease in the absolute magnitude of stress. However, changing the encapsulation has no detectable effect on the gradient behind the shock in such polymeric systems.