This thesis describes a number of optical spectroscopic measurements in novel oneudand two dimensional photonic crystals patterned in a slab waveguide.udTwo dimensional photonic crystals have also been embedded in a ridge waveguideudto confine light to the plane containing the photonic crystal. Linear characterizationudof these structures revealed a photonic band gap. Non linear measurements revealedudpulse· compression, negative differential transmission and showed that the ridgeudwaveguide nonlinear response dwarfs that of the photonic crystal.udPump-probe spectroscopy is used to study the nonlinear response ofudAlGaAsllnAlGaAs MQW one dimensional photonic crystals. The modulation of theudreflectivity spectra due to the refractive index change produced by two and three photonudinduced free-carriers was measured. Pump-induced blue-shifts in theudwavelength of photonic resonances were measured. These were followed by rapiduddecay - 25 ps. The blue-shifts in the photonic resonances were as large as 15 nm.udThe lifetime of free-carrier nonlinearities in one dimensional photonic crystals wasudfound to depend on the photonic crystal parameters, i.e. period, air fill factor andudetch depth. It was found that the free-carrier nonlinearities lifetime varied from 8 toud33.5 ps.udUltrafast tuning of the photonic resonances was obtained via the optical Kerr effectudand the optical (AC) Stark effect. Decay-less tuning was observed. The responseudtime was measured to be at FWHM - 300-400 fs.
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