Finite-Difference Time-Domain Integration of Ultrafast Dynamics in Optical Resonators
AIR FORCE RESEARCH LAB BOLLING AFB DC
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This thesis discusses optical pulse discrimination in nonlinear resonators. The goal is to design a system which interacts strongly with an optical pulse of a specific temporal shape but rejects all others. The resonator is a Fabry-Perot cavity that has a nonlinear absorbing material in the center. When an optical field of the resonant frequency is incident upon the cavity, the field intensity increases inside the cavity. As this happens, the refractive index of the nonlinear material is modified by the intensity of the field. This causes the cavity to shift off resonance, since the change in index changes the relative wavelength of the optical field inside the cavity. This, in turn, causes the intensity in the middle section to decrease, since the frequency of the field is no longer matched to the resonance frequency of the cavity. However, if the incident fields frequency is dynamically changed to track the shifting resonance of the cavity, the intensity of the interior field can be built up higher than is possible with just monochromatic light. By looking at the total absorption in the cavity, it will be possible to determine whether or not a pulse of the correct temporal shape has passed through the system. The absorption is strongly dependent on the shape of the incoming pulse, since only a pulse that tracks the nonlinear change in index will build up to a high enough intensity to be measured.