Nanomolar levels of the hypoxanthine in NaOH electrolyte cantaining copper(Ⅱ) can be determined by anodic stripping voltammetry at a glassy carbon electrode. In the present article hypoxanthine Cu + is shown to be ...Nanomolar levels of the hypoxanthine in NaOH electrolyte cantaining copper(Ⅱ) can be determined by anodic stripping voltammetry at a glassy carbon electrode. In the present article hypoxanthine Cu + is shown to be adsorbed on the electrode surface in the presence of an excess of copper(Ⅱ). After accumulation period, hypoxanthine Cu + was stripped from the electrode surface and the anodic current coming near to the oxidation of Cu(Ⅰ) to Cu(Ⅱ) was measured. A linear calibration curve in the range of 5 nmol/L 1.5 mmol/L hypoxanthine, with a detection limit of 0.5 nmol/L hypoxanthine were obtained.展开更多
Theoretical calculations of the quantum confined Stark shift for the first heavy hole exciton(hhl-el)in step quantum well are given.A significant change in Stark shift is achieved in specially stepped potential shape,...Theoretical calculations of the quantum confined Stark shift for the first heavy hole exciton(hhl-el)in step quantum well are given.A significant change in Stark shift is achieved in specially stepped potential shape,which is more than two times larger than the conventional rectangular quantum well.The structure has the advantage of a large change in absorption,which is one of the best candidates for the optical modulators utilizing the quantum confined Stark effect(QCSE)in GaAs/AlGaAs.Relations between QCSE and stepped structure are discussed in the optimization for large Stark shift.展开更多
In this letter,we present the observation of phase conjugation at 9.27μm in a GaAs/AlGaAs multiple step quantum well structure.The response is caused by the nearly resonant intersubband transition.The magnitude of X^...In this letter,we present the observation of phase conjugation at 9.27μm in a GaAs/AlGaAs multiple step quantum well structure.The response is caused by the nearly resonant intersubband transition.The magnitude of X^((3))determined by this phase conjugation method is about 8×10^(-5)esu and the phase conjugate reflectivityηis about 6×10^(-3)uncorrected for Fresnel reflections.展开更多
We have observed transverse electric(TE)and transverse magnetic(TM)intersubband infrared absorption peaks in GaAs/AlGaAs step multiquantum wells(SMQW).The energy splitting between TE and TM is 13meV.The high conversio...We have observed transverse electric(TE)and transverse magnetic(TM)intersubband infrared absorption peaks in GaAs/AlGaAs step multiquantum wells(SMQW).The energy splitting between TE and TM is 13meV.The high conversion efficiency of second harmonic signal due to intersubband transition in the GaAs/AlGaAs SMQW with a waveguiding surface-emitting structure have been obtained.The second harmonic generation(SffG)obeys wave vector conservation and propagates perpendicular to the waveguide surface which shows that the nonlinear polarization field for SHG may be TE as well as TM active.The existence of strong surface-emitting second harmonic signal also offers solid evidence of TE polarization active intersubband transition in GaAs/AlGaAs SMQW structure.展开更多
We report the fabrication of high temperature superconducting YBa_(2)Cu_(3)O_(7-x) thin films on CaNdA1O_(4)(100) substrate by pulsed laser deposition.Films have excellent features.X-ray diffraction patterns show that...We report the fabrication of high temperature superconducting YBa_(2)Cu_(3)O_(7-x) thin films on CaNdA1O_(4)(100) substrate by pulsed laser deposition.Films have excellent features.X-ray diffraction patterns show that thin films are epitaxial with c-axis orientation normal to the surface of su bstrate.The four-terminal measurements indicate the zero resistance temperature of 92.1 K,and transition width of 0.7K,the critical current density of 3×10^(6)A/cm^(2)at 77K and under zero magnetic field.展开更多
The properties of intersubband transition of GaAs/A1_(x)Ga_(1-x)As multiple quantum wells with various well widths and doped-well concentrations have been studied.Both theoretical and experimental results are in good ...The properties of intersubband transition of GaAs/A1_(x)Ga_(1-x)As multiple quantum wells with various well widths and doped-well concentrations have been studied.Both theoretical and experimental results are in good agreement.For the appropriate well width and higher doping concentration,we directly observed two intersubband absorption peaks from E_(1)→E_(2) and E_(2)→E_(3) transitions in well.The experimental results and theoretical analysis are given.展开更多
According to the theory of DBR, with the P-type DBR as an example, the electrical characteristics and optical reflection of the DBR are analyzed by studying the energy band structure with various graded region widths ...According to the theory of DBR, with the P-type DBR as an example, the electrical characteristics and optical reflection of the DBR are analyzed by studying the energy band structure with various graded region widths and doping densities. The width and doping density of graded region are decided through a comparative study. The P-type DBR of 980 nm VCSELs is designed with Al0.9Ga0.1As and Al0.1Ga0.9As selected as the high and low refractive index material for the DBR. The 980 nm bottom VCSELs, which consists of 30 pairs P-type DBR and 28 pairs N-type DBR, are then fabricated. In P-type DBR, the width of graded region is 0.02 μm and the uniformity doping concentration is 2.5×10^18cm^-3. Its reflectivity is 99.9%. In N-type DBR, the width of graded region is also 0.02 μm and the uniformity doping concen- tration is 2×10^18cm^-3. Its reflectivity is 99.3%. The I-V curve shows that the series resistance of the device is about 0.05Ω. According to the theory of DBR, with the P-type DBR as an example, the electrical characteristics and optical reflection of the DBR are analyzed by studying the energy band structure with various graded region widths and doping densities. The width and doping density of graded region are decided through a comparative study. The P-type DBR of 980 nm VCSELs is designed, with Al0.9Ga0.1As and Al0.1Ga0.9As selected as the high and low refractive index material for the DBR. The 980 nm bottom VCSELs, which consist of 30 pairs P-type DBR and 28 pairs N-type DBR, are then fabricated. In P-type DBR, the width of graded region is 0.02μm and the uniformity doping concentration is 2.5×10^18cm^-3. Its reflectivity is 99.9%. In N-type DBR, the width of graded region is also 0.02 μm and the uniformity doping concentration is 2×10^18cm^-3. Its refiectivity is 99.3%. The I-V curve shows that the series resistance of the device is about 0.05Ω.展开更多
We report high-energy tunable 6.5-12 μm ps mid-infrared radiation generation based on OPA pumped using 1064 nm laser in LISe crystal.We simulated the relationship between the idler energy and crystal length.An optimu...We report high-energy tunable 6.5-12 μm ps mid-infrared radiation generation based on OPA pumped using 1064 nm laser in LISe crystal.We simulated the relationship between the idler energy and crystal length.An optimum LISe length of 4 mm was used to enhance the idler energy experimentally.At a pump energy of ~9.4 mJ, energy levels of ~146 and of ~27 μJ are generated at 6.5 μm and 12 μm, respectively.The highest energy of ~205 μJ is achieved at 8.1 μm at a pump energy of ~19 mJ.Finally, the angular and spectral width acceptance are measured.展开更多
文摘Nanomolar levels of the hypoxanthine in NaOH electrolyte cantaining copper(Ⅱ) can be determined by anodic stripping voltammetry at a glassy carbon electrode. In the present article hypoxanthine Cu + is shown to be adsorbed on the electrode surface in the presence of an excess of copper(Ⅱ). After accumulation period, hypoxanthine Cu + was stripped from the electrode surface and the anodic current coming near to the oxidation of Cu(Ⅰ) to Cu(Ⅱ) was measured. A linear calibration curve in the range of 5 nmol/L 1.5 mmol/L hypoxanthine, with a detection limit of 0.5 nmol/L hypoxanthine were obtained.
文摘Theoretical calculations of the quantum confined Stark shift for the first heavy hole exciton(hhl-el)in step quantum well are given.A significant change in Stark shift is achieved in specially stepped potential shape,which is more than two times larger than the conventional rectangular quantum well.The structure has the advantage of a large change in absorption,which is one of the best candidates for the optical modulators utilizing the quantum confined Stark effect(QCSE)in GaAs/AlGaAs.Relations between QCSE and stepped structure are discussed in the optimization for large Stark shift.
文摘In this letter,we present the observation of phase conjugation at 9.27μm in a GaAs/AlGaAs multiple step quantum well structure.The response is caused by the nearly resonant intersubband transition.The magnitude of X^((3))determined by this phase conjugation method is about 8×10^(-5)esu and the phase conjugate reflectivityηis about 6×10^(-3)uncorrected for Fresnel reflections.
基金Supported by the National Natural Science Foundation of China.
文摘We have observed transverse electric(TE)and transverse magnetic(TM)intersubband infrared absorption peaks in GaAs/AlGaAs step multiquantum wells(SMQW).The energy splitting between TE and TM is 13meV.The high conversion efficiency of second harmonic signal due to intersubband transition in the GaAs/AlGaAs SMQW with a waveguiding surface-emitting structure have been obtained.The second harmonic generation(SffG)obeys wave vector conservation and propagates perpendicular to the waveguide surface which shows that the nonlinear polarization field for SHG may be TE as well as TM active.The existence of strong surface-emitting second harmonic signal also offers solid evidence of TE polarization active intersubband transition in GaAs/AlGaAs SMQW structure.
基金the National Center for Research and Development on Superconductivity of China。
文摘We report the fabrication of high temperature superconducting YBa_(2)Cu_(3)O_(7-x) thin films on CaNdA1O_(4)(100) substrate by pulsed laser deposition.Films have excellent features.X-ray diffraction patterns show that thin films are epitaxial with c-axis orientation normal to the surface of su bstrate.The four-terminal measurements indicate the zero resistance temperature of 92.1 K,and transition width of 0.7K,the critical current density of 3×10^(6)A/cm^(2)at 77K and under zero magnetic field.
基金This research was supported by National Natural Science Foundation。
文摘The properties of intersubband transition of GaAs/A1_(x)Ga_(1-x)As multiple quantum wells with various well widths and doped-well concentrations have been studied.Both theoretical and experimental results are in good agreement.For the appropriate well width and higher doping concentration,we directly observed two intersubband absorption peaks from E_(1)→E_(2) and E_(2)→E_(3) transitions in well.The experimental results and theoretical analysis are given.
基金Supported partially by the National Natural Science Foundation of China (Grant Nos. 60636020, 60676034, 60577003, 60706007)
文摘According to the theory of DBR, with the P-type DBR as an example, the electrical characteristics and optical reflection of the DBR are analyzed by studying the energy band structure with various graded region widths and doping densities. The width and doping density of graded region are decided through a comparative study. The P-type DBR of 980 nm VCSELs is designed with Al0.9Ga0.1As and Al0.1Ga0.9As selected as the high and low refractive index material for the DBR. The 980 nm bottom VCSELs, which consists of 30 pairs P-type DBR and 28 pairs N-type DBR, are then fabricated. In P-type DBR, the width of graded region is 0.02 μm and the uniformity doping concentration is 2.5×10^18cm^-3. Its reflectivity is 99.9%. In N-type DBR, the width of graded region is also 0.02 μm and the uniformity doping concen- tration is 2×10^18cm^-3. Its reflectivity is 99.3%. The I-V curve shows that the series resistance of the device is about 0.05Ω. According to the theory of DBR, with the P-type DBR as an example, the electrical characteristics and optical reflection of the DBR are analyzed by studying the energy band structure with various graded region widths and doping densities. The width and doping density of graded region are decided through a comparative study. The P-type DBR of 980 nm VCSELs is designed, with Al0.9Ga0.1As and Al0.1Ga0.9As selected as the high and low refractive index material for the DBR. The 980 nm bottom VCSELs, which consist of 30 pairs P-type DBR and 28 pairs N-type DBR, are then fabricated. In P-type DBR, the width of graded region is 0.02μm and the uniformity doping concentration is 2.5×10^18cm^-3. Its reflectivity is 99.9%. In N-type DBR, the width of graded region is also 0.02 μm and the uniformity doping concentration is 2×10^18cm^-3. Its refiectivity is 99.3%. The I-V curve shows that the series resistance of the device is about 0.05Ω.
文摘We report high-energy tunable 6.5-12 μm ps mid-infrared radiation generation based on OPA pumped using 1064 nm laser in LISe crystal.We simulated the relationship between the idler energy and crystal length.An optimum LISe length of 4 mm was used to enhance the idler energy experimentally.At a pump energy of ~9.4 mJ, energy levels of ~146 and of ~27 μJ are generated at 6.5 μm and 12 μm, respectively.The highest energy of ~205 μJ is achieved at 8.1 μm at a pump energy of ~19 mJ.Finally, the angular and spectral width acceptance are measured.
