In this thesis the effects of single photon and multi-photon excitation on protoplasts from Arabidopsis thaliana are compared. Time-lapsed micro-spectroscopy at high spatial resolution is employed to study the response of chloroplasts within the protoplasts from Arabidopsis thaliana. We have found that the fluorescence spectra of chloroplasts exhibits dramatic changes and the protoplasts are rapidly damaged under multi-photon excitation as a result of pulsed laser illumination. In contrast, single photon excitation of chloroplasts with cw laser is relatively inert to the vitality of the protoplasts. In addition to, we have built an ultrafast laser excited cryogenic micro-spectroscopy setup to study the photoluminescence of PPV thin film. We found that the spectrum of PPV¡¦s photoluminescence should shift toward longer wavelength and the non-radiative transition should be suppressed as a result of longer electron coherence length at low temperature.

In this study, we have developed a high performance multi-photon microscopic system to perform second- harmonic (SH) imaging on a tooth and a KTP crystal . The high sensitivity of the system allows acquisition rate of 300 seconds/frame with resolution at 512¡Ñ512 pixels. The surface SH signal generated from the tooth and the KTP crystal is also carefully verified through micro-spectroscopy, polarization rotation and wavelength tuning. In this way, we can ensure the authenticity of the signal. KTP crystal and the enamel that encapsulates the dentine is known to possess highly ordered structures. The anisotropy of the structure is revealed in the microscopic SH images of the tooth and the KTP crystal samples.

In this study, we have successfully developed a high performance transmission mode Laser scanning for SHG imaging. This setup is capable of acquiring images of size 512¡Ñ512 pixels at a rate of 5.4 seconds/frame. The of samples can thus be imaged, which reflects the samples¡¦ structure and symmetry.