Singlet oxygen (1O2) is commonly recognized to be a major phototoxic component for inducing the biological damage during photodynamic therapy (PDT). In this study, a novel configuration of a thermoelectrically-cooled near-infrared sensitive InGaAs camera was developed for imaging of photodynamically-generated 1O2 luminescence. The validation of 1O2 luminescence images for solution samples was performed with the model photosensitizer Rose Bengal (RB). Images of 1O2 luminescence generated in blood vessels in vivo in a well-controlled dorsal skinfold window chamber model were also recorded during PDT. This study demonstrated the capacity of the newly-developed imaging system for imaging of 1O2 luminescence, and the first reported images of 1O2 luminescence in blood vessels in vivo. This system has potential for elucidating the mechanisms of vascular targeted PDT.
A route of delivering ultra-short laser pulses through a polarization-maintaining single-mode fiber has been investigated experimentally. The group velocity dispersion was well compensated, and the self-phase modulation was depressed in fiber. Finally, a 40-fs laser pulse with the energy of 70 pJ was obtained at the output of the transmitted fiber with the length up to 4 m in our fiber-delivery system. The route exhibits distinguishing features of compactness and flexibility, and this 40-fs laser pulse can be used not only to generate broadband terahertz (THz) radiation but also to detect broadband THz radiation, which is much better than the 150-fs laser pulse used previously.
The numerical simulation of terahertz generation and detection in the interaction between femtosecond laser pulse and
photoconductive material has been reported in this paper. The simulation model based on the Drude-Lorentz theory is
used, and takes into account the phenomena that photo-generated electrons and holes are separated by the external bias
field, which is screened by the space-charge field simultaneously. According to the numerical calculation, the terahertz
time-domain waveforms and their Fourier-transformed spectra are presented under different conditions. The simulation
results indicate that terahertz generation and detection properties of photoconductive antennas are largely influenced by
three major factors, including photo-carriers' lifetime, laser pulse width and pump laser power. Finally, a simple model
has been applied to simulate the detected terahertz pulses by photoconductive antennas with various photo-carriers'
lifetimes, and the results show that the detected terahertz spectra are very different from the spectra radiated from the
emitter.
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