Optical studies of A1GaAs photonic crystal waveguides.

This thesis describes a number of optical spectroscopic measurements in novel one
and two dimensional photonic crystals patterned in a slab waveguide.
Two dimensional photonic crystals have also been embedded in a ridge waveguide
to confine light to the plane containing the photonic crystal. Linear characterization
of these structures revealed a photonic band gap. Non linear measurements revealed
pulse· compression, negative differential transmission and showed that the ridge
waveguide nonlinear response dwarfs that of the photonic crystal.
Pump-probe spectroscopy is used to study the nonlinear response of
AlGaAsllnAlGaAs MQW one dimensional photonic crystals. The modulation of the
reflectivity spectra due to the refractive index change produced by two and three photon
induced free-carriers was measured. Pump-induced blue-shifts in the
wavelength of photonic resonances were measured. These were followed by rapid
decay - 25 ps. The blue-shifts in the photonic resonances were as large as 15 nm.
The lifetime of free-carrier nonlinearities in one dimensional photonic crystals was
found to depend on the photonic crystal parameters, i.e. period, air fill factor and
etch depth. It was found that the free-carrier nonlinearities lifetime varied from 8 to
33.5 ps.
Ultrafast tuning of the photonic resonances was obtained via the optical Kerr effect
and the optical (AC) Stark effect. Decay-less tuning was observed. The response
time was measured to be at FWHM - 300-400 fs.