A high characteristic temperature （T0） of 200K from a 1.3μm AlInGaAs/AlInAs single-quantum-well laser diode with the asymmetric waveguide layer structure under CW operation at 20 to 80℃ was obtained,which is the b...A high characteristic temperature （T0） of 200K from a 1.3μm AlInGaAs/AlInAs single-quantum-well laser diode with the asymmetric waveguide layer structure under CW operation at 20 to 80℃ was obtained,which is the best result reported in the laser diodes （LDs） of the same active materials structure and emitting wave- length. AllnGaAs as an active layer,therefore,is very promising for the fabrication of long-wavelength LDs with excellent high-temperature performance. It is found that the asymmetric waveguide layer structure can decrease optical absorption and improve the high-temperature performance and catastrophic optical damage threshold of LDs.展开更多
The cutoff wavenumbers of elliptical waveguides were calculated by using isogeomtric analysis method （IGA）. With NURBS basis functions in IGA, the computational model was consistent with geometric model imported fro...The cutoff wavenumbers of elliptical waveguides were calculated by using isogeomtric analysis method （IGA）. With NURBS basis functions in IGA, the computational model was consistent with geometric model imported from CAD system. The field variable （longitudinal electric/magnetic field） was constructed by the same NURBS basis functions as the representation of geometric model. In the refinement procedure used to get a more accurate solution, communication with original CAD system is unnecessary and the geometric shape is kept unchanged. The Helrnholtz equation is weakened to a set of general eigenvalue equation by virtual work principal with diseretized degree-of-freedom on control points. Elliptical waveguides with three typical eccentricities, 0.1, 0.5 and 0.9, are calculated by IGA with different size mesh. The first four cutoff wavenumbers are obtained even in coarse mesh and the RMS of first 25 cutoff wavenumbers has much more swift convergence rate with decreasing the mesh size than traditional FEM. The accuracy and robustness of the proposed method are validated by elliptical waveguides, and also the method can be applied to waveguides with arbitrary cross sections.展开更多
Dependence of conductance of corrugated graphene quantum dot(CGQD)on geometrical features includinglength,width,connection and edge is investigated by the first principles calculations.The results demonstrate that the...Dependence of conductance of corrugated graphene quantum dot(CGQD)on geometrical features includinglength,width,connection and edge is investigated by the first principles calculations.The results demonstrate that theconductance of CGQD with different geometrical features is different from each other.The positions and amplitudesof discrete levels in densities of states and transmission coefficients are sensitive to geometrical features.The I-Vcharacteristics of graphene are modified by size and edge,it is surprise the current does not change monotonously butoscillatory with length.And they are slight change for different connections.展开更多
The modulation depth, defined according to practical modulation results, which changes with the microwave power and its frequency, is significant for systems utilizing the frequency-shift characteristic of the LiNbO3 ...The modulation depth, defined according to practical modulation results, which changes with the microwave power and its frequency, is significant for systems utilizing the frequency-shift characteristic of the LiNbO3 waveguide Electro-Optic Intensity Modulator （EOIM）. By analyzing the impedance mismatch between the microwave source and the EOIM, the effective voltage applied to the RF port of the EOIM is deprived from the microwave power and its frequency. Associating with analyses of the phase velocity mismatch between the microwave and the optical wave, the theoretical modulation depth has been obtained, which is verified by experimental results. We provide a method to choose the appropriate modulation depth to optimize the desired sideband through proper transmission bias for the system based on the frequency-shift characteristic of the EOIM.展开更多
文摘A high characteristic temperature （T0） of 200K from a 1.3μm AlInGaAs/AlInAs single-quantum-well laser diode with the asymmetric waveguide layer structure under CW operation at 20 to 80℃ was obtained,which is the best result reported in the laser diodes （LDs） of the same active materials structure and emitting wave- length. AllnGaAs as an active layer,therefore,is very promising for the fabrication of long-wavelength LDs with excellent high-temperature performance. It is found that the asymmetric waveguide layer structure can decrease optical absorption and improve the high-temperature performance and catastrophic optical damage threshold of LDs.
基金Project(GZ566) supported by the China-German Joint Research FoundationProjects(51138011, 51109134) supported by the National Natural Science Foundation of China
文摘The cutoff wavenumbers of elliptical waveguides were calculated by using isogeomtric analysis method （IGA）. With NURBS basis functions in IGA, the computational model was consistent with geometric model imported from CAD system. The field variable （longitudinal electric/magnetic field） was constructed by the same NURBS basis functions as the representation of geometric model. In the refinement procedure used to get a more accurate solution, communication with original CAD system is unnecessary and the geometric shape is kept unchanged. The Helrnholtz equation is weakened to a set of general eigenvalue equation by virtual work principal with diseretized degree-of-freedom on control points. Elliptical waveguides with three typical eccentricities, 0.1, 0.5 and 0.9, are calculated by IGA with different size mesh. The first four cutoff wavenumbers are obtained even in coarse mesh and the RMS of first 25 cutoff wavenumbers has much more swift convergence rate with decreasing the mesh size than traditional FEM. The accuracy and robustness of the proposed method are validated by elliptical waveguides, and also the method can be applied to waveguides with arbitrary cross sections.
文摘Dependence of conductance of corrugated graphene quantum dot(CGQD)on geometrical features includinglength,width,connection and edge is investigated by the first principles calculations.The results demonstrate that theconductance of CGQD with different geometrical features is different from each other.The positions and amplitudesof discrete levels in densities of states and transmission coefficients are sensitive to geometrical features.The I-Vcharacteristics of graphene are modified by size and edge,it is surprise the current does not change monotonously butoscillatory with length.And they are slight change for different connections.
基金supported by Program for New Century Excellent Talents in University(No.NCET-06-0925)
文摘The modulation depth, defined according to practical modulation results, which changes with the microwave power and its frequency, is significant for systems utilizing the frequency-shift characteristic of the LiNbO3 waveguide Electro-Optic Intensity Modulator （EOIM）. By analyzing the impedance mismatch between the microwave source and the EOIM, the effective voltage applied to the RF port of the EOIM is deprived from the microwave power and its frequency. Associating with analyses of the phase velocity mismatch between the microwave and the optical wave, the theoretical modulation depth has been obtained, which is verified by experimental results. We provide a method to choose the appropriate modulation depth to optimize the desired sideband through proper transmission bias for the system based on the frequency-shift characteristic of the EOIM.
