The hybridly mode-locked dye laser pulses with pulse energies of several nanojoules at 585 nm were amplified up to several millijoules per pulse at 20 Hz repetition rate. The output pulses of 1.5 mJ/pulse with a gain of $3\times 10^6$ were obtained from a synchronously pumping dye amplifier composed of three quasi-longitudinally pumped dye cells. The pulse width of amplified pulses was 0.57 ps which was about twice as short as that of input pulses. On the other hand, we have demonstrated the amplification method of femtosecond dye laser pulses suppressing the pulse broadening effect. In the amplification of 185 fs dye laser pulses with negative group velocity dispersion, the pulse broadening effect was insignificant because the group velocity dispersion was compensated by the positive group velocity dispersion in the amplifier system. The amplified pulses had a pulse width of 215 fs with 4.2 nm fwhm at 585 nm.
Based upon the high-power ultrashort pulse lasers, we have investigated the time-resolved differential transmittance spectra (DTS) of nanostructure semiconductors in order to understand the photoinduced absorption processes. The photoinduced absorption of $CdS_{0.4}Se_{0.6}$ nanostructure semiconductors below the band gap is believed to be contributed by the carriers trapped at the semiconductor-glass interfaces within less than 1 ps after photoexcitation and its decay dynamics depends strongly on the excitation intensity. At low excitation intensity, the excited carriers are trapped at point defects distributed over the nanocrystal interfaces. Such carriers give rise to the long-lived photoinduced absorption with a lifetime of 3.2 ns. On the other hand, at high excitation intensity the transient absorption profile with a fast (about 50 ps) and a slow decay components (3.2 ns) was simultaneously observed. The carriers shallowly trapped at the semiconductor-glass interfaces induce the short-lived photoindued absorption with time constants of about 3.5 and 80 ps which vary significantly with a change in the excitation intensity. Such ultrafast decay phenomena of photoinduced absorption are attributed to the nongeminate electron-hole recombination processes.
In this dissertation, we have confirmed, for the first time to our knowledge, the semiconductor-glass interface states including deep trap, shallow trap, and quasi-continuum states of $CdS_0.4Se_0.6$nanostructure semiconductors doped in glasses. We reported the experimental results such as ultrafast trapping of excited carriers, saturation of long-lived photoinduced absorption, and strong dependence of its decay dynamics on the excitation intensity. Based on our results, a new model for photoinduced absorption of nanostructure semiconductors doped in glasses was suggested. Our results suggest that the electronic energy states at the semiconductor-glass interfaces of nanostructure semiconductors doped in glasses have a strong influence on the nonlinear absorption even near and above the band gap.
