This thesis investigates the behaviour of light in waveguides with cores composed of a negative refractive index material. The ability of these structures to drastically slow and even halt light pulses is studied. The Finite-Difference Time-Domain computational simulation method is used to simulate these structures and the results produced are compared against those from analytic calculations. It is observed that pulses in waveguides with thinner cores have smaller group ve- locities. By recording the change of the pulse's magnetic field with distance the pulse's effective refractive index is extracted and is found to match that calculated analytically. Reducing the magnitude of the core's intrinsic refractive index is also found to reduce the pulse's group velocity. Due to the loss present in current negative refractive index materials, a method of supplying gain to the propagating pulse was investigated. This was achieved by placing a strip of gain material within the waveguide cladding. The gain supplied is found to increase when the separation between the strip and core is decreased, when the width of the strip is increased and when the width of the waveguide's core is reduced. Including the gain material creates a frequency region where the pulse experiences gain and the real part of its effective index is negative. Through recording the change in the pulse's magnetic field over time its complex frequency was extracted. Using the pulse's energy velocity it was possible to convert between the complex frequency and complex wavevector. The use of a prism to couple to the waveguide was also examined. This allowed exceedingly slow modes, of the order of 0.00002c to be excited. It was discovered that keeping the prism in place once the light had coupled into the waveguide caused the value of the pulse's maximum wavevector component to shift.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:555932 |
| Date | January 2011 |
| Creators | Kirby, Edmund |
| Publisher | University of Surrey |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://epubs.surrey.ac.uk/804655/ |
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