Study Of Ultrafast Dynamics And Application On Framing Camera Of The Light-induced-carriers Of GaAs

It is nearly impossible to improve the time resolution of the traditional framingcameras any more for the limitation of electronic devices. In order to make ultrafastdiagnostic devices with picosecond time resolution, and build the ultrafast diagnosticsystem based on the refraction index change produced by the light-induced-carrier,this dissertation theoretically studies the refractive index change of the semiconductorGallium Arsenide (GaAs), or the sensitivity of the ultrafast detecting system, with thechange of the wavelength of the incidence probe light when the concentration ofelectrons is given. Apart from the work I have done, this part contains manyconclusions and results of the known research. As I know, some equations I derivedhave not been seen from related articles or books. Parts of the conclusions aresimulated by computer after theoretical derivation. And the final data show that theamount of refractive index change increases as the wave length decreases and as thedensity of the carriers, which is within the set range, increases while the photonenergy of the probe light is smaller than the band gap energy. Otherwise, if the photonenergy of the probe light is larger than band gap energy, along with the rising of thecarrier density, the photon energy of the probe light which have larger amount ofrefractive index change increases.Pump-probe technology is used to experimentally investigate the carrierdynamics property of GaAs, or the time resolution of the ultrafast detecting systembased on the carrier dynamics. The results show that the intensity of the pump lightcould be expressed by the ultrafast carrier dynamics property of the semiconductor. Itmeans that the time resolution of the kind of devices which is based on this ultrafastdynamics phenomenon will be very high. Based on previous research and data, as awhole, the duration of the carrier density change could be controlled on picosecondlevel on condition that the material is good enough. Considering the noise from thepump light in the experiment, the weak part of the refractive index change was bleached by the noise and can not be observed directly. According to the experimentresults of this dissertation, the duration of the fierce refractive index change is about800femtosecond, based on the femtosecond pulse laser source used in thisdissertation.