研究了由理想线偏振片和单轴双折射晶体波片组成的双折射滤光片倾斜放置时的二阶色散和三阶色散特性，包括波片厚度、光线入射角和光轴旋转角的变化对二阶和三阶色散的影响。 还给出了双折射滤光片的群延迟表达式，并就色散特性与GT干涉仪进行了详细比较。

Milli-Joule, femtosecond laser pulses have been used to propel microbeads for the first time. The microbeads of three different materials (iron, glass, and polystyrene) are used, weighting from 0.84 mg to 1.4 mg with a diameter range of 0.7-1.1 mm. Experimental parameters such as focused beam spot diameter, pulse energy, and pulse width are carefully varied to investigate their respective influences on the specific ablative laser propulsion. It is found that both the momentum coupling efficiency and the overall energy conversion efficiency from light energy to kinetic energy are greater for shorter laser pulses. A typical value of the momentum coupling efficiency of 5.0 dyne/W for iron beads is obtained. It is also evident that for metallic and non-metallic microbeads the momentum coupling efficiency has different variation tendencies versus the focused beam spot diameter.

We report experimental results of drilling micro holes in Al, Mo, Ti, Cu, Ag, Au, and brass thin metal foils in air using 60-femtosecond Ti:sapphire laser pulses. The influence of laser parameters and material properties on drilling processes at the sub-10-micron scale has been examined. Comparison of hole drilling using 60-fs pulses with that using 50-ps and 10-ns pulses at an energy fluence of 15 J=cm2 indicates that a significant amount of melting is present in both ps and ns regimes, whereas with fs pulses, fewer and much smaller droplets from the molten phase are observed.

The origin of the dominant pulse-shaping effects in a coupled-cavity mode-locked (CCM) KCl: Tl laser is described Inferences relating to pulse-profile detail have been deduced from spectral and temporal data that were recorded for a range of period-mismatch conditions for the main and control cavities of the CCM laser.

By making numerical simulations the influence of resonant absorption in Er-doped fibres on the propagation characteristics of femtosecond pulses has been examined. It is shown that when the fibre background dispersion is relatively small compared to the dispersion caused by absorption, the pulses propagating in an unpumped Er-doped fibre can be either compressed or broadened, depending on whether the spectrum of the launched pulse is on the longer or shorter wavelength side of the absorption center. The phase distortion due to absorption has a more severe impact on the temporal profile of a propagating pulse than the corresponding amplitude attenuation. A switching of the sign of the actual fibre dispersion on one side of the absorption center occurs and this can lead to a change of pulse propagation characteristics from a soliton regime to a non-solitonic regime.

The dynamic process of intense 50 fs laser ablation of aluminum is investigated by ultrafast timeresolved microscopy. A stripe pattern preceding phase explosion is clearly seen in the shadowgraph of 1 ns time delay. Intermittent material ejections are observed within the ejected plume after 2.5 and 7 ns time delay, respectively, which may be attributed to the material response to the generation of an extremely strong thermoelastic wave. Similar processes are also recorded in the ablation of silicon and glass samples, except for the glass samples, the intermittent material ejections are not found.

We investigate spectral modulation in self-mode-locked femtosecond Ti: sapphire lasers. The spectra of the laser output and of the light reflected from intracavity surfaces can exhibit a periodic modulation due to the laser rod acting as an intracavity birefringent filter. These spectral features vary greatly between the two orthogonally polarized components of the laser beam. The free spectral range and depth of the observed modulation depend on the crystal length and cavity alignment respectively. The qualitative features of the observed spectra can be explained using a simple model of the coupling between polarization states of the laser due to the birefringence of the laser rod.

We present an experimental observation on spectrum evolution of femtosecond pulses in filamentation by introducing a hollow fiber as a probe and moving it along the filament. The results show that at a particular position of the filament, the pulse spectrum from the hollow fiber expands to its maximum, which corresponds to the shortest pulse duration existing in the filament. The influence of gas pressure on the spectrum broadening is also examined.

The mutual transition dynamics between nonthermal and thermal dominant ablation processes is investigated in the hole-drilling and line-scribing experiments on aluminum samples with intense 50 fs to 24 ps laser pulses. It is found that a critical pulse width that separates the two different ablation regimes monotonically reduces with the increasing laser fluence. Theoretical analyses suggest that the complex interplay between photomechanical stress fragmentation and phase explosion could be responsible for these observations. A semiempirical transition law between the two ablation regimes is introduced, which is consistent with measured experimental data.

Laser-induced breakdown spectra (LIBS) produced in ambient air and pure gases with tightly focused, micro Joule, fhmtoseeond Ti: sapphire laser pulses have been studied experimentally. The breakdown region typically measures around 10μm in diameter and 120μm in length. Both line spectrum and blue-shifted continuum spectrum arc rccorded [br air, N2, O2, Ar, Kr, and Xe when the optical intensity reaclles 1014W/cm2, using 40 fspulses. It is also found that the profile of the continuum varies only slightly for different gases. For a given gas the continuum profile changes along different positions of the narrow micro plasma track. In parficular, the blue-shifted broad confinuum is stronger at the initial posgion of the plasma track (closer to the focal lens), whereas the line spectrum is mare dominant when light collection is made at the fnrther end of the plasma track. Unlike the results reported by others for longer pulses, higher energy and also larger plasma zone, the majority of line spectrum we obtained is found around 800nm, the central wavelength of the input Ti: sapphire pulses.