Because the general multi-wavelength UV-Visible absorbance detector cannot avoid the noise and drift resulting from the intensity fluctuation of the light source,a dual beam multi-wavelength UV-Visible detector based ...Because the general multi-wavelength UV-Visible absorbance detector cannot avoid the noise and drift resulting from the intensity fluctuation of the light source,a dual beam multi-wavelength UV-Visible detector based on CCD was designed. The ray of light source is divided into a signal ray and a reference ray by the beam splitter after it passes through the chopper. The signal ray shines into the sample cell. The signal ray passing through the sample cell falls onto a concave mirror which focuses it onto a slot that is imaged on one portion of COD by a concave grating. The reference ray is imaged on the other portion of COD by the concave grating after the slot. The signal spectrum, the reference spectrum and the dark current of COD can be measured on the same CCD under the cooperation of the optical system and accessorial circuits. The real-time compensation for the signal spectrum by using the reference spectrum and the dark current of OCD can effectively depress the noise and drift of the detector. The short-term noise is 10^-5 AU and the drift is 10^-1 AU/h.展开更多
Resonance enhancement has been increasingly employed in the emergent felntosecond stimu- lated Raman spectroscopy （FSRS） to selectively monitor molecular structure and dynamics with improved spectral and temporal re...Resonance enhancement has been increasingly employed in the emergent felntosecond stimu- lated Raman spectroscopy （FSRS） to selectively monitor molecular structure and dynamics with improved spectral and temporal resolutions and signal-to-noise ratios. Such joint eflforts by the technique- and application-oriented scientists and engineers have laid the foundation for exploiting the tunable FSRS methodology to investigate a great variety of photosensitive systems and elucidate the underlying functional mechanisms on molecular time scales. Dur- ing spectral analysis, peak line shapes remain a major concern with an intricate dependence on resonance conditions. Here, we present a comprehensive study of line shapes by tuning the Rarnan pump wavelength from red to blue side of the ground-state absorption band of the fluorescent dye rhodarnine 6G in solution. Distinct line shape patterns in Stokes and anti-Stokes FSRS as well as from the low to high-frequency modes highlight the competition between multiple third-order and higher-order nonlinear pathways, governed by difl^rent res- onance conditions achieved by Raman pump and probe pulses. In particular, the resonance condition of probe wavelength is revealed to play an important role in generating circular line shape changes through oppositely phased dispersion via hot luminescence （HL） pathways. Meanwhile, on-resonance conditions of the Rarnan pump could promote excited-state vibrational modes which are broadened and red-shifted from the coincident ground-state vibrational modes, posing challenges for spectral analysis. Certain strategies in tuning the Raman pump and probe to characteristic regions across an electronic transition band are discussed to improve the FSRS usability and versatility as a powerful structural dynamics toolset to advance chemical, physical, materials, and biological sciences.展开更多
A high performance heterojunction organic ultraviolet photodetector based on NPB and Bphen has been fabricated. A trans- parent conducting polymer PEDOT：PSS coated quartz substrate instead of ITO coated glass substra...A high performance heterojunction organic ultraviolet photodetector based on NPB and Bphen has been fabricated. A trans- parent conducting polymer PEDOT：PSS coated quartz substrate instead of ITO coated glass substrate as anode is propitious to detect shorter wavelength ultraviolet light. As a result, the device shows a low dark current density, a high responsivity of 502 mA/W and a detectivity of 2.67x1012 cm Hz1/Zfw which is illuminated by a 220 nm ultraviolet light with an intensity of 1.6 mW/cm2. Moreover, the performance of the PEDOT：PSS transparent electrode device is better than the semi-transparent A1 electrode device electrode because of the higher transmittance and electrode properties.展开更多
Uncooled In As Sb photoconductors were fabricated. The photoconductors were based on In As0.05Sb0.95 and In As0.09Sb0.91 thick epilayers grown on In As substrates by melt epitaxy(ME). Ge immersion lenses were set on t...Uncooled In As Sb photoconductors were fabricated. The photoconductors were based on In As0.05Sb0.95 and In As0.09Sb0.91 thick epilayers grown on In As substrates by melt epitaxy(ME). Ge immersion lenses were set on the photoconductors. The cutoff wavelength of In As0.09Sb0.91 detectors is obviously extended to 11.5 μm, and that of In As0.05Sb0.95 detectors is 8.3 μm. At room temperature, the peak detectivity of Dλp* at wavelength of 6.8 μm and modulation frequency of 1 200 Hz is 1.08×109 cm·Hz1/2·W-1 for In As0.09Sb0.91 photoconductors, the detectivity D* at wavelength of 9 μm is 7.56×108 cm·Hz1/2·W-1, and that at 11 μm is 3.92×108 cm·Hz1/2·W-1. The detectivity of In As0.09Sb0.91 detectors at the wavelengths longer than 9 μm is about one order of magnitude higher than that of In As0.05Sb0.95 detectors, which rises from the increase of arsenic(As) composition in In As0.09Sb0.91 materials.展开更多
文摘Because the general multi-wavelength UV-Visible absorbance detector cannot avoid the noise and drift resulting from the intensity fluctuation of the light source,a dual beam multi-wavelength UV-Visible detector based on CCD was designed. The ray of light source is divided into a signal ray and a reference ray by the beam splitter after it passes through the chopper. The signal ray shines into the sample cell. The signal ray passing through the sample cell falls onto a concave mirror which focuses it onto a slot that is imaged on one portion of COD by a concave grating. The reference ray is imaged on the other portion of COD by the concave grating after the slot. The signal spectrum, the reference spectrum and the dark current of COD can be measured on the same CCD under the cooperation of the optical system and accessorial circuits. The real-time compensation for the signal spectrum by using the reference spectrum and the dark current of OCD can effectively depress the noise and drift of the detector. The short-term noise is 10^-5 AU and the drift is 10^-1 AU/h.
基金supported by the U.S.National Science Foundation CAREER grant(CHE-1455353)the Oregon State University(OSU) Research Equipment Reserve Fund(Spring 2014)to C.Fang(USTC9603)the Wei Family Private Foundation in supporting C.Chen(USTC 0903) during his graduate studies at OSU Chemistry
文摘Resonance enhancement has been increasingly employed in the emergent felntosecond stimu- lated Raman spectroscopy （FSRS） to selectively monitor molecular structure and dynamics with improved spectral and temporal resolutions and signal-to-noise ratios. Such joint eflforts by the technique- and application-oriented scientists and engineers have laid the foundation for exploiting the tunable FSRS methodology to investigate a great variety of photosensitive systems and elucidate the underlying functional mechanisms on molecular time scales. Dur- ing spectral analysis, peak line shapes remain a major concern with an intricate dependence on resonance conditions. Here, we present a comprehensive study of line shapes by tuning the Rarnan pump wavelength from red to blue side of the ground-state absorption band of the fluorescent dye rhodarnine 6G in solution. Distinct line shape patterns in Stokes and anti-Stokes FSRS as well as from the low to high-frequency modes highlight the competition between multiple third-order and higher-order nonlinear pathways, governed by difl^rent res- onance conditions achieved by Raman pump and probe pulses. In particular, the resonance condition of probe wavelength is revealed to play an important role in generating circular line shape changes through oppositely phased dispersion via hot luminescence （HL） pathways. Meanwhile, on-resonance conditions of the Rarnan pump could promote excited-state vibrational modes which are broadened and red-shifted from the coincident ground-state vibrational modes, posing challenges for spectral analysis. Certain strategies in tuning the Raman pump and probe to characteristic regions across an electronic transition band are discussed to improve the FSRS usability and versatility as a powerful structural dynamics toolset to advance chemical, physical, materials, and biological sciences.
基金supported by the National Natural Science Foundation of China (Grant No. 50972007)the Beijing Municipal Natural Science Foundation (Grant No. 4092035)+3 种基金the National Basic Research Program of China (973 Program) of the Ministry of Science and Technology of China(Grant No. 2011CB932703)the National Science Fund for Distinguished Young Scholars (Grant No. 60825407)the Special Items Fund of the Beijing Municipal Commission of Educationthe Opened Fund of the State Key Laboratory of Integrated Optoelectronics
文摘A high performance heterojunction organic ultraviolet photodetector based on NPB and Bphen has been fabricated. A trans- parent conducting polymer PEDOT：PSS coated quartz substrate instead of ITO coated glass substrate as anode is propitious to detect shorter wavelength ultraviolet light. As a result, the device shows a low dark current density, a high responsivity of 502 mA/W and a detectivity of 2.67x1012 cm Hz1/Zfw which is illuminated by a 220 nm ultraviolet light with an intensity of 1.6 mW/cm2. Moreover, the performance of the PEDOT：PSS transparent electrode device is better than the semi-transparent A1 electrode device electrode because of the higher transmittance and electrode properties.
基金supported by the Fundamental Research Funds for the Central Universities in China
文摘Uncooled In As Sb photoconductors were fabricated. The photoconductors were based on In As0.05Sb0.95 and In As0.09Sb0.91 thick epilayers grown on In As substrates by melt epitaxy(ME). Ge immersion lenses were set on the photoconductors. The cutoff wavelength of In As0.09Sb0.91 detectors is obviously extended to 11.5 μm, and that of In As0.05Sb0.95 detectors is 8.3 μm. At room temperature, the peak detectivity of Dλp* at wavelength of 6.8 μm and modulation frequency of 1 200 Hz is 1.08×109 cm·Hz1/2·W-1 for In As0.09Sb0.91 photoconductors, the detectivity D* at wavelength of 9 μm is 7.56×108 cm·Hz1/2·W-1, and that at 11 μm is 3.92×108 cm·Hz1/2·W-1. The detectivity of In As0.09Sb0.91 detectors at the wavelengths longer than 9 μm is about one order of magnitude higher than that of In As0.05Sb0.95 detectors, which rises from the increase of arsenic(As) composition in In As0.09Sb0.91 materials.
