The conversion efficiency and noise figure (NF) of the silicon-on-insulator (SOI) waveguide-based wavelength converter are investigated with the coupled equations. The effects of the pump power, the nonlinear absorpti...The conversion efficiency and noise figure (NF) of the silicon-on-insulator (SOI) waveguide-based wavelength converter are investigated with the coupled equations. The effects of the pump power, the nonlinear absorption and the waveguide length on the conversion efficiency and noise figure are discussed. The conversion efficiency decreases with the increasing pump power and the noise figure is degraded due to the two-photon absorption (TPA) and the TPA-induced free-carrier absorption (FCA) at the higher pump power. With the increasing of the free carrier lifetime, the conversion efficiency will decrease and the noise figure will increase accordingly. The optimal waveguide length depends on the pump power and the free carrier lifetime. In practical applications, the high conversion efficiency and low noise figure can be achieved by choosing suitable parameters of the silicon waveguide.展开更多
The Nd^(3+) doped fluorochlorozirconate(FCZ) glass was prepared by melt-quenching method. The 3.9 μm emission from Nd^(3+) ions is attributed to the two-photon absorption process. The strong emission transition at 3...The Nd^(3+) doped fluorochlorozirconate(FCZ) glass was prepared by melt-quenching method. The 3.9 μm emission from Nd^(3+) ions is attributed to the two-photon absorption process. The strong emission transition at 3.9 μm fluorescence peak intensity, corresponding to the ~4G_(11/2)→~2K_(13/2) transition, is directly proportional to the NaCl concentration. With the increase of the Cl-ions amount, the mid-infrared(MIR) luminescent intensity is significantly enhanced. Additionally, the Judd-Ofelt(J-O) parameter ?_2 is larger than that of the fluorozirconate(FZ) glass, which indicates the covalency of the bond between RE ions and ligand is stronger as Cl-ions substitution of F-ions in chloride FZ glass. The X-ray diffraction(XRD) patterns show that the amorphous glassy state keeps the FZ glass network structure. In brief, the advantageous spectroscopic characteristics make the Nd^(3+)-doped FCZ glass be a promising candidate for application of 3.9 μm emission.展开更多
Enhancing the photoluminescence and depressing the background emission are important problems in rare earth ion-doped materials. In this letter, the two-photon absorption （TPA） probability in a Pr3＋ ion system is e...Enhancing the photoluminescence and depressing the background emission are important problems in rare earth ion-doped materials. In this letter, the two-photon absorption （TPA） probability in a Pr3＋ ion system is enhanced by a factor of 12.3 by a π-phase step scanning of ultrashort laser pulses. This level is significantly higher than that achieved by a transform-limit pulse. However, the laser intensity of shaped pulse is reduced to 37% of the initial transform-limited pulse. In this method, the TPA probability can also be reduced to 58%. Furthermore, the el＇feet of the shift of the intermediate energy level and the bandwidth of final states on TPA probability is discussed.展开更多
The fluorescence power from biological tissue excited by a femtosecond laser pulse compared with excitation power does not appear to obey a simple quadratic relationship given by the steady non-linear theory. A more r...The fluorescence power from biological tissue excited by a femtosecond laser pulse compared with excitation power does not appear to obey a simple quadratic relationship given by the steady non-linear theory. A more reliable analysis is developed based on transient two-photon absorption because the response time of two-photon absorption is longer than the width of a femtosecond pulse. Good agreement is obtained between the theoretical analysis and the experimental results of fluorescence power versus excitation power. This letter offers potential value to non-linear optics in biological tissues.展开更多
Nonlinear absorption of monolayer graphene suspension is studied in the wavelength of 800 nm using Z-scan method with 50-fs pulses. Nonlinear absorption property of graphene suspension at different excitation intensit...Nonlinear absorption of monolayer graphene suspension is studied in the wavelength of 800 nm using Z-scan method with 50-fs pulses. Nonlinear absorption property of graphene suspension at different excitation intensities is compared. Large reverse saturable absorptions are found and believed to arise from two- photon absorption.展开更多
A short review of experimental and theoretical results on the large angle cross sections ＂γγ→ twomesons＂ and the form factors γ＊γ→ P = {π, η, η＇} is given.
Ultrafast spectroscopy of semiconductor saturable absorber mirror （SESAM） is measured using a femtosec- ond pump-probe experiment. This allows dynamic responses of SESAM in the cavity to be concluded by ultrafast sp...Ultrafast spectroscopy of semiconductor saturable absorber mirror （SESAM） is measured using a femtosec- ond pump-probe experiment. This allows dynamic responses of SESAM in the cavity to be concluded by ultrafast spectroscopy. Change in reflection is measured as a function of pump-probe delay for different pump excitation fluences. Change of nonlinear reflection of SESAM is measured as a function of incident light energy density. When the excitation fluence increases, nonlinear change in ultrafast spectroscopy of SESAM becomes increasingly significant. When SESAM is pumped by an ultrahigh excitation fluence, the energy density of which is approximately 1400 μJ/cm2, two-photon absorption can be observed visibly in its ultrafast spectroscopy.展开更多
Repetition rate-dependent absorbance measurements of synthetic fused silica at 193-nm irradiation are performed in tile range of 50-1000 Hz with an ArF laser calorimeter. The ＂apparent＂ single- and two- photon absor...Repetition rate-dependent absorbance measurements of synthetic fused silica at 193-nm irradiation are performed in tile range of 50-1000 Hz with an ArF laser calorimeter. The ＂apparent＂ single- and two- photon absorption coefficients are determined by measuring the laser fiuence-dependent absorbance of fused silica samples with different thicknesses to separate the surface absorption and bulk absorption. The measurement results indicate a reversible nonlinear increase of both apparent single- and two-photon absorption coefficients with increasing repetition rate for the synthetic fused silica, whereas the surface absorption shows no dependence on the repetition rate.展开更多
基金supported by the Major State Basic Research Development Program of China (No.2010CB328304)the National Natural Science Foundation of China (No.60807022)the Discipline Co-construction Project of Beijing Munnicipal Commission of Education (No.YB20081001301)
文摘The conversion efficiency and noise figure (NF) of the silicon-on-insulator (SOI) waveguide-based wavelength converter are investigated with the coupled equations. The effects of the pump power, the nonlinear absorption and the waveguide length on the conversion efficiency and noise figure are discussed. The conversion efficiency decreases with the increasing pump power and the noise figure is degraded due to the two-photon absorption (TPA) and the TPA-induced free-carrier absorption (FCA) at the higher pump power. With the increasing of the free carrier lifetime, the conversion efficiency will decrease and the noise figure will increase accordingly. The optimal waveguide length depends on the pump power and the free carrier lifetime. In practical applications, the high conversion efficiency and low noise figure can be achieved by choosing suitable parameters of the silicon waveguide.
基金supported by the National High Technology Research and Development Program of China(No.2013AA014201)the Natural Science Foundation of Tianjin(Nos.11JCYBJC00300,14JCZDJC31200,15JCYBJC16700 and 15JCYBJC16800)+1 种基金the National Key Foundation for Exploring Scientific Instrument of China(No.2014YQ120351)International Cooperation Program from Science and Technology of Tianjin(No.14RCGHGX00872)
文摘The Nd^(3+) doped fluorochlorozirconate(FCZ) glass was prepared by melt-quenching method. The 3.9 μm emission from Nd^(3+) ions is attributed to the two-photon absorption process. The strong emission transition at 3.9 μm fluorescence peak intensity, corresponding to the ~4G_(11/2)→~2K_(13/2) transition, is directly proportional to the NaCl concentration. With the increase of the Cl-ions amount, the mid-infrared(MIR) luminescent intensity is significantly enhanced. Additionally, the Judd-Ofelt(J-O) parameter ?_2 is larger than that of the fluorozirconate(FZ) glass, which indicates the covalency of the bond between RE ions and ligand is stronger as Cl-ions substitution of F-ions in chloride FZ glass. The X-ray diffraction(XRD) patterns show that the amorphous glassy state keeps the FZ glass network structure. In brief, the advantageous spectroscopic characteristics make the Nd^(3+)-doped FCZ glass be a promising candidate for application of 3.9 μm emission.
基金supported by the National Natural Science Foundation of China(Nos.5113200 and 411027403)the National Special Science Research Program of China(Nos.2010CB923203 and 2011CB808105)the Shanghai Municipal Science and Technology Commission(Nos.11JC1403500 and 10PJ1403400)
文摘Enhancing the photoluminescence and depressing the background emission are important problems in rare earth ion-doped materials. In this letter, the two-photon absorption （TPA） probability in a Pr3＋ ion system is enhanced by a factor of 12.3 by a π-phase step scanning of ultrashort laser pulses. This level is significantly higher than that achieved by a transform-limit pulse. However, the laser intensity of shaped pulse is reduced to 37% of the initial transform-limited pulse. In this method, the TPA probability can also be reduced to 58%. Furthermore, the el＇feet of the shift of the intermediate energy level and the bandwidth of final states on TPA probability is discussed.
基金supported by the Natural Science Foundation of Fujian Province of China under Grant No.2009J01277
文摘The fluorescence power from biological tissue excited by a femtosecond laser pulse compared with excitation power does not appear to obey a simple quadratic relationship given by the steady non-linear theory. A more reliable analysis is developed based on transient two-photon absorption because the response time of two-photon absorption is longer than the width of a femtosecond pulse. Good agreement is obtained between the theoretical analysis and the experimental results of fluorescence power versus excitation power. This letter offers potential value to non-linear optics in biological tissues.
基金supported by the Natural Science Foundation of the Naval University of Engineering under Grant No.201200000039
文摘Nonlinear absorption of monolayer graphene suspension is studied in the wavelength of 800 nm using Z-scan method with 50-fs pulses. Nonlinear absorption property of graphene suspension at different excitation intensities is compared. Large reverse saturable absorptions are found and believed to arise from two- photon absorption.
基金supported in part by the RFBR grant 07-02-00361-a
文摘A short review of experimental and theoretical results on the large angle cross sections ＂γγ→ twomesons＂ and the form factors γ＊γ→ P = {π, η, η＇} is given.
基金supported by the Ministry of Science,Research,and the Arts of Baden-Wrttemberg State of Germany and the Chinese Scholarship Council
文摘Ultrafast spectroscopy of semiconductor saturable absorber mirror （SESAM） is measured using a femtosec- ond pump-probe experiment. This allows dynamic responses of SESAM in the cavity to be concluded by ultrafast spectroscopy. Change in reflection is measured as a function of pump-probe delay for different pump excitation fluences. Change of nonlinear reflection of SESAM is measured as a function of incident light energy density. When the excitation fluence increases, nonlinear change in ultrafast spectroscopy of SESAM becomes increasingly significant. When SESAM is pumped by an ultrahigh excitation fluence, the energy density of which is approximately 1400 μJ/cm2, two-photon absorption can be observed visibly in its ultrafast spectroscopy.
文摘Repetition rate-dependent absorbance measurements of synthetic fused silica at 193-nm irradiation are performed in tile range of 50-1000 Hz with an ArF laser calorimeter. The ＂apparent＂ single- and two- photon absorption coefficients are determined by measuring the laser fiuence-dependent absorbance of fused silica samples with different thicknesses to separate the surface absorption and bulk absorption. The measurement results indicate a reversible nonlinear increase of both apparent single- and two-photon absorption coefficients with increasing repetition rate for the synthetic fused silica, whereas the surface absorption shows no dependence on the repetition rate.
