We demonstrate the ultrafast imaging of a submillimeter bar chart that is either hidden behind glass diffusers or inside a solution of polystyrene spheres,using an ultrafast optical Kerr gate (OKG).The results show th...We demonstrate the ultrafast imaging of a submillimeter bar chart that is either hidden behind glass diffusers or inside a solution of polystyrene spheres,using an ultrafast optical Kerr gate (OKG).The results show that the time-resolved imaging of the target in the turbid media with an optical depth of 11.4 is achieved using the OKG with a 1.6 ps opening time.The image contrast is improved by about 70% compared with the shadowgraph imaging.展开更多
We investigate the optical Kerr effect of SrTiO3 (STO) crystal,of which the nonlinear response time was measured to be less than 200fs,while the nonlinear refractive index is estimated to be 2.16 × 10^(-15)cm^(2)...We investigate the optical Kerr effect of SrTiO3 (STO) crystal,of which the nonlinear response time was measured to be less than 200fs,while the nonlinear refractive index is estimated to be 2.16 × 10^(-15)cm^(2)/W.Using theoptical Kerr gate (OKG) technique with an STO crystal as the Kerr medium,we obtain narrow-bandwidth and symmetric gated spectra from a supercontinuum generated in distilled water by a femtosecond laser.The experimental results show superiority compared with the gated spectra obtained using OKG with CS2 as the Kerr medium,demonstrating that STO crystal is a promising OKG medium.展开更多
A simple method using an 800-nm femtosecond laser and chemical selective etching is developed for fabrication of high-aspect-ratio grooves in silicon carbide. Micro grooves with an aspect ratio of approximately 40 are...A simple method using an 800-nm femtosecond laser and chemical selective etching is developed for fabrication of high-aspect-ratio grooves in silicon carbide. Micro grooves with an aspect ratio of approximately 40 are obtained. The morphology and chemical compositions of the grooves are analyzed using a scanning electronic microscope equipped with an energy dispersive x-ray spectroscopy. The formation mechanism of SiC grooves is attributed to the chemical reactions of the laser induced structural changes with a mixed solution of hydrofluoric acid and nitric acid. In addition, the effects of laser irradiation parameters on the aspect ratio of the grooves are investigated.展开更多
The thermal effects on the processing of type-I IR fiber Bragg gratings(FBGs)using a femtosecond laser with a phase mask are investigated.Thermal effects are significantly suppressed by using interval exposure mode an...The thermal effects on the processing of type-I IR fiber Bragg gratings(FBGs)using a femtosecond laser with a phase mask are investigated.Thermal effects are significantly suppressed by using interval exposure mode and reducing the tension on the fiber.FBGs with improved photo-induced refractive index modulation are fabricated in the standard telecom fiber.The index modulation reaches 1.6×10^(-3).The reflectivity and bandwidth are measured to be-0.36 dB and 1.27 nm,respectively.展开更多
We investigate the influence of the coherent effect on femtosecond time-resolved Z-scan measurements using a degenerate pump-probe Z-scan technique.The time response of the light-induced transient grating(LITG)of Bi_(...We investigate the influence of the coherent effect on femtosecond time-resolved Z-scan measurements using a degenerate pump-probe Z-scan technique.The time response of the light-induced transient grating(LITG)of Bi_(2)O_(3)-B_(2)O_(3)-SiO_(2)(BI)glass shows a valley-peak variation,which has an obvious influence on the time-resolved Z-scan measurements.The valley-peak variation of the LITG signals with the delay time in BI glass is due to coherent transient energy transfer between positively chirped pump and probe pulses.The influence of the LITG effect on the closed-aperture time-resolved Z-scan measurements could be reduced by adjusting the position of the aperture transversely.展开更多
The influence of the coherent artifact in a semiconductor Ga-doped ZnO film on femtosecond pump-probe measurement is studied.The coherent artifact mixed into the pump-probe signal can be directly inspected by detectin...The influence of the coherent artifact in a semiconductor Ga-doped ZnO film on femtosecond pump-probe measurement is studied.The coherent artifact mixed into the pump-probe signal can be directly inspected by detecting the background-free first-order diffraction signal induced by the interference between the pump and probe pulses.Experimental results show that by varying the polarization angle or adjusting the relative intensity between the pump and probe pulses,the coherent artifact can be eliminated from the pump-probe measurement.展开更多
A series of squarylium cyanine dyes with different substituents were synthesized and the third-order optical nonlinearities of their ground and excited states were investigated by backward degenerate four-wave-mixing....A series of squarylium cyanine dyes with different substituents were synthesized and the third-order optical nonlinearities of their ground and excited states were investigated by backward degenerate four-wave-mixing.For the ground state,the molecular hyperpolarizabilityγg increases with the red-shift of the absorption peakλabmax,of the squaraine with different substituents,whereas for the excited-state molecular hyperpolarizabilityγe,the nonlinear enhancementγe/γg decreases,which may indicate that in the excited state the electron accepting-donating ability of different substituents changes in the reverse order compared with the order in the ground state.展开更多
The ground-and the excited-state nonlinearities of two new copolymers are investigated in nanosecond scale at 1064 nm.It is found that the excited-state susceptibility is dramatically larger than the corresponding gro...The ground-and the excited-state nonlinearities of two new copolymers are investigated in nanosecond scale at 1064 nm.It is found that the excited-state susceptibility is dramatically larger than the corresponding ground-state susceptibility for each sample.The experimental results also give evidence that superlattice structure of the copolymers can enhance,especially for the excited state,the molecular hyperpolarizabilities significantly.This enhancement may be attributed to the confinement effect of the pump-induced carriers.展开更多
We report the measured results of non-resonant nonlinearity by degenerate four-wave mixing for Cu2O nanopartides having central diameter of 9 nm.The value of x^(3) obtained in a 10ns pulse experiment is 8.48×1O^(...We report the measured results of non-resonant nonlinearity by degenerate four-wave mixing for Cu2O nanopartides having central diameter of 9 nm.The value of x^(3) obtained in a 10ns pulse experiment is 8.48×1O^(-10) esu,and the nonlinear response time of the sample is estimated to be in the order of nanosecond.展开更多
基金Supported by National Basic Research Program of China under Grant No 2012CB921804the National Natural Science Foundation of China under Grant Nos 91123028 and 11074197.
文摘We demonstrate the ultrafast imaging of a submillimeter bar chart that is either hidden behind glass diffusers or inside a solution of polystyrene spheres,using an ultrafast optical Kerr gate (OKG).The results show that the time-resolved imaging of the target in the turbid media with an optical depth of 11.4 is achieved using the OKG with a 1.6 ps opening time.The image contrast is improved by about 70% compared with the shadowgraph imaging.
基金Supported by the National Natural Science Foundation of China under Grant Nos 91123028 and 11074197the National Basic Research Program of China under Grant No 2012CB921804the Eyas Project of the Academy of Opto-Electronics,Chinese Academy of Sciences。
文摘We investigate the optical Kerr effect of SrTiO3 (STO) crystal,of which the nonlinear response time was measured to be less than 200fs,while the nonlinear refractive index is estimated to be 2.16 × 10^(-15)cm^(2)/W.Using theoptical Kerr gate (OKG) technique with an STO crystal as the Kerr medium,we obtain narrow-bandwidth and symmetric gated spectra from a supercontinuum generated in distilled water by a femtosecond laser.The experimental results show superiority compared with the gated spectra obtained using OKG with CS2 as the Kerr medium,demonstrating that STO crystal is a promising OKG medium.
基金Supported by the National Natural Science Foundation of China under Grant Nos 91123028 and 61235003, and the National Basic Research Program of China under Grant No 2012CB921804.
文摘A simple method using an 800-nm femtosecond laser and chemical selective etching is developed for fabrication of high-aspect-ratio grooves in silicon carbide. Micro grooves with an aspect ratio of approximately 40 are obtained. The morphology and chemical compositions of the grooves are analyzed using a scanning electronic microscope equipped with an energy dispersive x-ray spectroscopy. The formation mechanism of SiC grooves is attributed to the chemical reactions of the laser induced structural changes with a mixed solution of hydrofluoric acid and nitric acid. In addition, the effects of laser irradiation parameters on the aspect ratio of the grooves are investigated.
基金Supported by the National Basic Research Program of China under Grant No 2012CB921804the National Natural Science Foundation of China under Grant Nos 11204236 and 91123028.
文摘The thermal effects on the processing of type-I IR fiber Bragg gratings(FBGs)using a femtosecond laser with a phase mask are investigated.Thermal effects are significantly suppressed by using interval exposure mode and reducing the tension on the fiber.FBGs with improved photo-induced refractive index modulation are fabricated in the standard telecom fiber.The index modulation reaches 1.6×10^(-3).The reflectivity and bandwidth are measured to be-0.36 dB and 1.27 nm,respectively.
基金Supported by the National Natural Science Foundation of China under Grant Nos 61235003,11204236,61205129the Fundamental Research Funds for the Central Universities.
文摘We investigate the influence of the coherent effect on femtosecond time-resolved Z-scan measurements using a degenerate pump-probe Z-scan technique.The time response of the light-induced transient grating(LITG)of Bi_(2)O_(3)-B_(2)O_(3)-SiO_(2)(BI)glass shows a valley-peak variation,which has an obvious influence on the time-resolved Z-scan measurements.The valley-peak variation of the LITG signals with the delay time in BI glass is due to coherent transient energy transfer between positively chirped pump and probe pulses.The influence of the LITG effect on the closed-aperture time-resolved Z-scan measurements could be reduced by adjusting the position of the aperture transversely.
基金by the National Natural Science Foundation of China under Grant No 11074197the Specialized Research Fund for the Doctoral Program of Higher Education of China under the Grant No 200806980022。
文摘The influence of the coherent artifact in a semiconductor Ga-doped ZnO film on femtosecond pump-probe measurement is studied.The coherent artifact mixed into the pump-probe signal can be directly inspected by detecting the background-free first-order diffraction signal induced by the interference between the pump and probe pulses.Experimental results show that by varying the polarization angle or adjusting the relative intensity between the pump and probe pulses,the coherent artifact can be eliminated from the pump-probe measurement.
基金the National Natural Science Foundation of China under Grant Nos.19734040,and 69778014.
文摘A series of squarylium cyanine dyes with different substituents were synthesized and the third-order optical nonlinearities of their ground and excited states were investigated by backward degenerate four-wave-mixing.For the ground state,the molecular hyperpolarizabilityγg increases with the red-shift of the absorption peakλabmax,of the squaraine with different substituents,whereas for the excited-state molecular hyperpolarizabilityγe,the nonlinear enhancementγe/γg decreases,which may indicate that in the excited state the electron accepting-donating ability of different substituents changes in the reverse order compared with the order in the ground state.
基金Supported by the National Natural Science Foundation of China under Grant No.19734004。
文摘The ground-and the excited-state nonlinearities of two new copolymers are investigated in nanosecond scale at 1064 nm.It is found that the excited-state susceptibility is dramatically larger than the corresponding ground-state susceptibility for each sample.The experimental results also give evidence that superlattice structure of the copolymers can enhance,especially for the excited state,the molecular hyperpolarizabilities significantly.This enhancement may be attributed to the confinement effect of the pump-induced carriers.
文摘We report the measured results of non-resonant nonlinearity by degenerate four-wave mixing for Cu2O nanopartides having central diameter of 9 nm.The value of x^(3) obtained in a 10ns pulse experiment is 8.48×1O^(-10) esu,and the nonlinear response time of the sample is estimated to be in the order of nanosecond.
