Nonlinear optical properties of one- and two-dimensional photonic crystal waveguides.
Contributors: Van Driel, Henry (supervisor)
Published: 2005
Language: eng
Number of pages: 162
Subjects: Physics Theses.
Description: The nonlinear optical properties of two photonic crystal waveguides are investigated. The first sample is a one-dimensional Bragg grating with a defect microstructured into an AlGaAs waveguide. The transmitted spectrum from the defect mode is tuned to longer or shorter wavelengths by varying (1) the spectral position of the incident pulse spectrum with respect to the defect mode, and (2) the pump intensity. The tuning is explained by self-phase modulation of the incident 250 fs pulses in the waveguide, and by the filtering properties of the defect mode.The second material is a two-dimensional GaAs/AlGaAs planar photonic crystal waveguide patterned with a square lattice of air holes. Several nonlinear optical properties are investigated in a reflection geometry for 150-fs s-polarized pulses, tuned from 1900 to 2000 nm. Strongly enhanced second-harmonic (SH) generation is observed when the fundamental beam, the SH beam, or both beams resonantly couple to leaky eigenmodes of the patterned waveguide. Compared with off-resonant conditions, SH enhancements >1200x are observed when both beams resonantly couple to leaky modes. The angular and spectral positions of the peaks are in good agreement with simulations. The enhanced SH generation is also a good diagnostic tool to monitor ultrafast tuning of leaky eigenmodes via free carrier injection. Pump and probe spectroscopy is used to measure blueshifts as large as 16 +/- 2 nm and 3.8 +/- 0.2 nm when either the incoming (1900 nm) fundamental or outgoing (950 nm) SH beams resonantly couple to leaky modes of the patterned waveguide for a pump fluence of 100 muJ/cm 2. Simulations incorporating carrier induced changes in the refractive index well-describe the differences in the shifts. Faster (pulse-width limited) tuning effects are observed via the optical Kerr effect for a 1900 nm pump and 1360 nm probe on resonance with modes of the patterned waveguide. A factor of 6 enhancement in the Kerr effect is related to the quality factor of the leaky mode. The results of this thesis may be used to develop the next generation of integrated photonic devices by providing a mechanism for all-optical switching and enhanced frequency conversion.
Notes: Thesis (Ph.D.)--University of Toronto, 2005.

Electronic version licensed for access by U. of T. users.

Source: Dissertation Abstracts International, Volume: 66-06, Section: B, page: 3207.