The ultrafast dynamics of third order nonlinearities of polyaniline(PAn)and polyaniline doped in polymethyl mathacrylate(PAn-PMMA)films are investigated using femtosecond absorption spectroscopy.An ultrafast initial e...The ultrafast dynamics of third order nonlinearities of polyaniline(PAn)and polyaniline doped in polymethyl mathacrylate(PAn-PMMA)films are investigated using femtosecond absorption spectroscopy.An ultrafast initial exciton deformation time of about 100fs is observed in PAn film.In PAn-PMMA film,the third-order nonlinearity results in an efficient two-photon absorption at about 2eV.展开更多
Optical information storage caused by photoinduced anisotropy in poly[4'-bis(N,N-oxyethylene)imino-4-nitroazobenzene succinyl]film is studied by two-wave mixing.Using Nd:YAG second-harmonic pulses(100ps),grating o...Optical information storage caused by photoinduced anisotropy in poly[4'-bis(N,N-oxyethylene)imino-4-nitroazobenzene succinyl]film is studied by two-wave mixing.Using Nd:YAG second-harmonic pulses(100ps),grating of orientation of azobenzene molecules is formed in the film by photoinduced anisotropy.Up to third-order diffraction was observed.After turning off one of the two pump lights,the signals remained.When the weaker one of two pump lights was turned off,the intensities of diffraction beams of another pump light almost did not decrease.The information recorded in the film can be 100%maintained for a long time(monitored over 100 days without obvious decrease).展开更多
We report the results of femtosecond spectroscopy studies on YBa_(2)Cu_(3)O_(7-x )and PrBa_(2)Cu_(3)O_(7-x )(x=0.1)epitaxial thin films at room temperature.The transient reSectivity signals ΔR(t)in the samples are co...We report the results of femtosecond spectroscopy studies on YBa_(2)Cu_(3)O_(7-x )and PrBa_(2)Cu_(3)O_(7-x )(x=0.1)epitaxial thin films at room temperature.The transient reSectivity signals ΔR(t)in the samples are consistent with a band filliitg model.The relaxation times of ΔR(t)in YBa_(2)Cu_(3)O_(7-x ) increase from less th&n 100 fs to more than Ips with increasing x and with substitution of Pr for Y.These results reveal that in high Tc superconductors decrease of carrier concentration slows down the carrier-phonon coupling.展开更多
The interaction of the electrons with the phonons in GaAs/AlGaAs quantum wells,quantum well wires,and quantum well boxes has been studied by meansuring their time resolved photoluminescence(PL)spectra.In the quantum w...The interaction of the electrons with the phonons in GaAs/AlGaAs quantum wells,quantum well wires,and quantum well boxes has been studied by meansuring their time resolved photoluminescence(PL)spectra.In the quantum well(Q W)system,relaxation time of the electron energy of the narrower well is shorter than that of the wider well.It is attributed to the stronger interaction of the electrons with the interface mode phonons.In the Q W wires and Q W boxes,the shortening of the relaxation time is obvious.It is due to the stronger electron-phonon interaction caused by the reduction of screening effect.Our experiments also demonstrated the incident laser intensity dependence of the relaxation time.展开更多
文摘The ultrafast dynamics of third order nonlinearities of polyaniline(PAn)and polyaniline doped in polymethyl mathacrylate(PAn-PMMA)films are investigated using femtosecond absorption spectroscopy.An ultrafast initial exciton deformation time of about 100fs is observed in PAn film.In PAn-PMMA film,the third-order nonlinearity results in an efficient two-photon absorption at about 2eV.
文摘Optical information storage caused by photoinduced anisotropy in poly[4'-bis(N,N-oxyethylene)imino-4-nitroazobenzene succinyl]film is studied by two-wave mixing.Using Nd:YAG second-harmonic pulses(100ps),grating of orientation of azobenzene molecules is formed in the film by photoinduced anisotropy.Up to third-order diffraction was observed.After turning off one of the two pump lights,the signals remained.When the weaker one of two pump lights was turned off,the intensities of diffraction beams of another pump light almost did not decrease.The information recorded in the film can be 100%maintained for a long time(monitored over 100 days without obvious decrease).
基金Supported by the National Center for Research and Development on Superconductivity of China.
文摘We report the results of femtosecond spectroscopy studies on YBa_(2)Cu_(3)O_(7-x )and PrBa_(2)Cu_(3)O_(7-x )(x=0.1)epitaxial thin films at room temperature.The transient reSectivity signals ΔR(t)in the samples are consistent with a band filliitg model.The relaxation times of ΔR(t)in YBa_(2)Cu_(3)O_(7-x ) increase from less th&n 100 fs to more than Ips with increasing x and with substitution of Pr for Y.These results reveal that in high Tc superconductors decrease of carrier concentration slows down the carrier-phonon coupling.
文摘The interaction of the electrons with the phonons in GaAs/AlGaAs quantum wells,quantum well wires,and quantum well boxes has been studied by meansuring their time resolved photoluminescence(PL)spectra.In the quantum well(Q W)system,relaxation time of the electron energy of the narrower well is shorter than that of the wider well.It is attributed to the stronger interaction of the electrons with the interface mode phonons.In the Q W wires and Q W boxes,the shortening of the relaxation time is obvious.It is due to the stronger electron-phonon interaction caused by the reduction of screening effect.Our experiments also demonstrated the incident laser intensity dependence of the relaxation time.
