Mesoscopic Studies On Light-Matter Interaction And Laser Field Characterization

The light-matter interaction and laser field characterization in the mesoscopic regime has thrived for the merging of photonics and nano technologies. We investigated this cutting-edge area in three different scopes including atom molecule in ultrafast lasers, femtosecond laser pulse in complex nanostructures and beads with radius around several microns in a laser trap.We first studied the photoionization of dihydrogen ion in ultrashort laser pulse by using numerical algorithm which evolves the time-dependenct Schrodinger equation (TDSE). We found that the charge-resonance-enhanced ionization (CREI) is absent when the dihydrogen ion is exposed in a subfemto- or attosecond laser pulse. And an exact time of the wavepacket returning to its parent molecule has been retrieved from the simulation. A novel method for deciding the internuclear distance from the 2D ionized wavepacket was also proposed. For the hydrogen cluster in an ultrashort pulse, on the other hand, we utilized classical model in our simulation since a quantum mechanics treatment needs nearly infinite resource for calculation. The maximum kinetic energy, kinetic energy spectrum and the number of ionized atoms relative to different intensity of the incident beam have been studied, and an empirical formula was derived to determine the intensity threshold of Coulomb Explosion.We introduced and demonstrated the Second HARmonic nano-Probe (SHARP) for characterizing the femtosecond laser pulse in a complex nano structure. The SHARP played the role of a localized signal source in the femtosecond pulse field and was capable of nonperturbingly characterizing the whole field by scanning in 3D with a resolution of about 100nm. A collinear-FROG configuration was used for both amplitude and phase information characterization. As the demonstration, we present in situ pulse characterization directly in the air core of a photonic crystal fiber and near the focal point of an objective.We proposed a novel technique for supercontinuum trap stiffness measurement using a confocal approach, in which the nonlinear photonic crystal fiber used for supercontinuum generation is also utilized as an effective confocal pinhole to track the motion of a trapped bead and as a scan head to realize rapid scanning of the optical trap. The confocal configuration gives a remarkable supression of the back reflection noise such that the Signal-Noise-Ratio has been improved.