Optical soliton controlled inverters in quadratic media and inhomogeneous waveguides.

摘要

This thesis studies nonlinear interaction between soliton-like optical pulses for building an all optical ultrafast NOT gate. The study begins by identifying cascaded quadratic nonlinearity as a physical mechanism that allows generation of multi-dimensional optical solitons, which are used as candidates for the demonstration of the ultrafast logic gate. First, 2 + 1D spatial solitons were generated and a controlled NOT gate was built with pico-second long chirped pulses. The experiments showed a gain of 2.5 and phase-insensitivity. Second, a walk-off compensating interaction was considered that satisfies gain, restoration and phase-insensitivity requirements for building a higher repetition rate logic device. The principle behind the operation of the second logic gate was experimentally demonstrated with 5muJ spatio-temporal soliton-like beams. Finally; the thesis concludes with theoretical studies on anti-guiding structures that allow shorter gate length, lower energy and lower threshold all optical logic gates.; Spatial soliton dragging gates are based on spatial shift of a pump beam in the presence of a weak signal beam. For building these logic gates, beams that maintain their shape by overcoming dispersion and diffraction, solitons, are necessary. Spatio-temporal solitons were first demonstrated with the help of tilted pulse in a chi(2) material [1]. A part of this thesis studies generation, linear propagation, nonlinear propagation, and measurement of the tilted-pulses in detail. Next we studied quadratic solitons. We performed numerical simulations to understand quadratic soliton interactions which lead to the experiments on the quadratic soliton inverter and walk-off compensation.; In order to build low energy logic gates numerical studies were carried out. The studies were focused on short gate length devices that require the use of spatial solitons. An anti-guide was found to efficiently assist the dragging interaction between a signal and a pump beam. A small signal beam was shown to switch the pump beam and achieve an order of magnitude improvement in the inverter switching energy. An extensive mathematical treatment based on multiscales was performed to derive the equations used in the numerical study.; The experimental work in this thesis also required the development of an ultrafast optical facility involving several diagnostics for time and space-time pulse shapes, materials, and interactions.