A theoretical study of negative refraction in two-dimensional hexagonal and square lattice photonic crystals is presented in this paper. Using dispersion surfaces, an investigation of the two mechanisms of this unusual phenomenon is done. Photonic crystals exhibiting negative refraction can be used to realize integrated flat lenses in order to obtain imaging with sub-wavelength resolution surpassing the diffraction limit of the conventional lenses.

A non defect waveguide based on self-collimation effect in two-dimensional photonic crystals is presented in this paper. An investigation to determine self-collimation frequency range in square and hexagonal lattice photonic crystals is realized. It is demonstrated the routing of two self-collimated Gaussian beams travelling through a hexagonal photonic crystal, on the same optical layer. Using the unique advantage of allowing self-collimated beams to cross each other without coupling, one can devise structureless interconnects for photonic integrated circuits.

A non inverting differential asymmetrical CMOS comparator with intrinsic hysteresis and adjustable asymmetry is presented in this paper. A widely tunable hysteresis window was obtained. The threshold voltage of the comparator is adjustable up to +150 mV of the input differential signal in 16 steps. The input differential signal is 400 mVpp with a frequency of 1 MHz. The bias current is 50 uA and the supply voltage is 3.3 V. The design was made in basic gpdk Cadence integrated circuits front to back 0.18 um CMOS technology. The response time was minimized and also the difference between the phases of the outputs was minimized. This comparator can be used, with good performance, in signal conditioning chains.