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Carbon nanoparticle colloids were prepared by Nd:YAG laser ablation of a carbon target immersed in water. The nanoparticles were collected on substrates and analyzed with micro-Raman spectroscopy and electron microscopy. Optical limiting properties of the carbon nanoparticle colloids towards 532 nm wavelength were characterized using a nanosecond Nd:YAG laser. A strong optical limiting response was detected for the carbon nanoparticle colloids with C 60 as reference at input laser fluence above 0.6 J/cm 2 . The effects of carbon nanoparticle concentrations upon the optical limiting behavior were also investigated. A convenient method for preparing carbon nanoparticle based optical limiters is proposed in this investigation.

Irradiance dependence of excitonic nonlinear absorption in Cadmium Sulfide (CdS) nanocrystals has been studied by using Z-scan method with nanosecond laser pulses.The wavelength dependence of nonlinear absorption has also been measured near the excitonic transition of 1S(e) -1S 3/2 (h). We observe the saturable absorption, which can be described by a third-order and a fifth-order nonlinear process for both 3.0-nmsized and 2.3-nm-sized CdS nanocrystals. The experimental results show that the excitonic nonlinear absorption of CdS nanocrystals is greatly enhanced with decreasing particle size. A two-level model is utilized to explain both irradiance and wavelength dependence of the excitonic nonlinearity.

Using a canonical pump-probe experimental technique, we studied the terahertz (THz) waves generation and detection via optical rectification and mixing in Czochralski-grown periodically poled Mg:Y:LiNbO 3 (PPLN) crystals. THz waves with frequencies at 1.37THz and 0.68 THz as well as 1.8 THz were obtained for PPLN with nonlinear grating periods of 30 and 60 µm, respectively. A general theoretical model was developed by considering the dispersion and damping of low frequency phonon-polariton mode. Our results show that THz waves are generated in forward and backward directions via pumping pulse rectification. The generated THz waves depend on the spectral shape of the laser pulses, quasi-phase mismatches and dispersion characteristics of a crystal.

The paper presents the development of a computer-aided process planning (CAPP) system based on Genetic Algorithm (GA) and Simulated Annealing (SA). The system employs an optimization modeling method that generates all the feasible operation-method alternatives. It also provides flexible optimization criteria that will satisfy the various needs from different job-shops and/or job-batches. Two search algorithms based on GA and SA respectively have been developed to solve the problem effectively. Also, the system provides manufacturability analysis function, which gives designers and job shop operators helpful information about the manufacturing.