Generation of the high efficiency high peak-power femtosecond blue optical pulse

The analysis and calculation of the compensation for the phase mismatch of the frequency-doubling using the frequency space chirp introduced from prisms are made. The result shows that suitable lens can compensate the phase mismatch in a certain extent resulting from wide femtosecond spectrum when the spectrum is space chirped. By means of this method, the experiment of second harmonic generation is carried out using a home-made femtosecond KLM Ti:sapphire laser and BBO crystal. The conversion efficiency of SHG is 63 %. The average output power of blue light is 320 mW. The central wavelength is 420 nm. The spectrum bandwidth is 5.5 nm. It can sustain the pulse width of 33.6 fs. The tuning range of blue light is 404-420 nm,when the femtosecond Ti:sapphire optical pulse is tuned using the prisms in the cavity.

Influence of polarization orientation of violet light on the diffraction efficiency of bacteriorhodopsin

When a grating is recorded in a bacteriorhodopsin film by two linear parallel polarized beams together with anauxiliary violet light, the diffraction efficiency has a dependence on the polarization orientation of the violet light as well as its intensity. A method for calculating the diffraction efficiency of gratings in bacteriorhodopsin is proposed based on the two-state photochromic model, considering the saturation effect and the polarization status of all the involved lights. It is found that the polarization orientation of the violet light produces an approximate-cosine and an approximate-sine modulation on the steady-state diffraction efficiency separately at low and high intensities, respectively. The parallel polarized violet light can improve the steady-state diffraction efficiency to a larger degree than the perpendicularly polarized violet light when both are at their optimal intensities. The optimal intensity for the parallel polarized violet light is lower than that of the perpendicular polarized one. Thus, the improvement of the steady-state diffraction efficiency is less sensitive to the intensity of perpendicular polarized violet light than to that of parallel polarized violet light. (C) 2008 Optical Society of America.

Internal quantum efficiency analysis of solar cell by genetic algorithm

To investigate factors limiting the performance of a GaAs solar cell, genetic algorithm is employed to fit the experimentally measured internal quantum efficiency (IQE) in the full spectra range. The device parameters such as diffusion lengths and surface recombination velocities are extracted. Electron beam induced current (EBIC) is performed in the base region of the cell with obtained diffusion length agreeing with the fit result. The advantage of genetic algorithm is illustrated.