Transmission properties of ultra-short pulses propagating through 1-D photonic crystals (PCs) with multiple cavities were experimentally investigated. Coupling between cavities is responsible for a wide resonance, inside the PC gap, suitable to distortion free propagation of 70 fs pulses at 800 nm. Geometry induced anomalous dispersion across the resonance allows chirp compensation of 70 fs pulses. We use an autocorrelator set-up in order to investigate chirp compensation effect by measuring the time duration of input and output pulses. Measurements are performed for different incidence angle. Results show that complete chirp compensation of 10 fs chirping occurs for an incidence angle of 20 deg.
Soliton formation in photorefractive crystals with strong optical activity is analyzed. We shall demonstrate that self-confinement of the laser beam is not enough to define such a beam "a soliton": in fact this state is completely define by both intensity and polarization soliton dynamics. We report here the characterization of the soliton state for CW and pulsed beams.
We have designed a one-dimensional photonic bandgap crystal to obtain perfect phase-matching conditions for noncollinear type II quadratic processes. The realized sample was 15 periods of Al(0.3)Ga(0.7)As/Al2O3, for a total length of 3.5um. Noncollinear type II phase-matching was obtained at 1510nm. We have experimentally verified the band structure characteristic as well as its perfect phase-matching for the noncollinear type II parametric process. Indeed, noncollinear type II second harmonic generation was obtained for the first time in a PBG crystal1. The experiment demonstrated that the breaking of symmetry, which is artificially induced in such a structure, and the field resonance effect give rise to a relatively efficient second harmonic generation even using a naturally isotropic material (AlGaAs). In fact, we report a nonlinear effective coefficient of the sample equal to (52±12) pm/V.
A comparison of laser tissue cutting on bovine muscle samples, by a CO2-CW laser and by a short-pulse (1 ps) amplified Ti-ZAFFIRE laser, has been performed. The CO2 laser application shows a large area of burned tissue, whose extension can be as large as 300-400 μm. The Ti-ZAFFIRE laser application shows a sharp cutting line, without burned tissue around. Numerical simulations of the temperature increasing using repetitive (1 kHz) short pulses reveal that after 1/10 sec of application of 0.5 W of average power, the local temperature has reached the evaporation value of about 300-350°C.
We discuss the possible implementation of a complete set of all-optical logical gates using second harmonic generation and parametric down-conversion. We also experimentally tested an all-optical single-bit half-adder made of a XOR and an AND gate, operating on binary stripes encoded as amplitude modulation of the transverse pattern of laser beam.
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