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In this study, an InGaN laser diode (LD) with InGaN–GaN–InGaN quantum barriers was proposed and studied systematically. The energy band diagrams, stimulated recombination rate, optical field distribution, current distribution near the active region, and power–current–voltage performance curves were investigated. The simulation results suggest that the LD with InGaN–GaN–InGaN quantum barriers has better performance than the LD with conventional GaN and InGaN quantum barriers because of the properly adjusted refraction index profile and energy band diagrams, which are advantageous to both the suppressed leakage of the optical field and electrons out of and the enhanced injection of holes into the active region. [ABSTRACT FROM AUTHOR]

In this study, with the objective of lowering the polarization without degrading the carrier confinement in the active region, an InGaN light-emitting diode with GaN/InGaN/GaN triangular (GIGT) quantum barriers (QBs) was proposed and studied systematically. When traditional GaN QBs were replaced by the GIGT QBs, the output power at 150 mA rose from 82.05 to 155.99 mW, and the efficiency droop was decreased from 51.0% to 16.5%. Simulation results indicated that these improvements could result from the effectively suppressed polarization field in the quantum wells and the markedly enhanced carrier confinement in the active region because of the appropriately modified energy band structure. [ABSTRACT FROM AUTHOR]

A high-performance nonscanning Fourier-transform spectrometer is reported that is composed mainly of a Wollaston prism array and a two-dimensional photodetector array. It is a substantial improvement over existing Wollaston prism based nonscanning Fourier-transform spectrometers because it offers finer spectral resolution and smaller size. Such spectrometers will find important applications in remote chemical and biological sensing, environmental monitoring, medical diagnosis, etc. Experimental results are consistent with theoretical analyses.

The implementation of non-zero-order joint-transform correlators (JTC's) is presented. The zero-order spectra (i.e., the autocorrelation power spectra) are removed from the joint-transform power spectrum by use of phase-shifting techniques by which the output diffraction and input spatial domain can more efficiently be utilized. Applications of the phase-shifting techniques to both conventional JTC's and phase-transformed input JTC's (PJTC's) are discussed. Compared with the conventional JTC, the PJTC has the advantages of higher light efficiency, a better signal-to-clutter ratio, and the simplicity to realize phase shifting. We anticipate that the proposed non-zero-order JTC's should have a significant impact on the future development of more efficient JTC's.

The electronic structures of a CdSe spherical quantum dot in a magnetic field are obtained by using an exact diagonalization method and a variational method within the effective-mass approximation. The dependences of the energies and wave functions of electron states, exciton binding energy, exciton transition energy, and exciton diamagnetic shift on the applied magnetic field are investigated theoretically in detail. It is observed that the degeneracy of magnetic quantum number m is removed due to the Zeeman effect when the magnetic field is present. For the states with m ≥ 0, the electron energies increase as the magnetic field increases. However, for the states with m < 0, the electron energies decrease to a minimum, and then increase with increasing the magnetic field. The energies and wave functions of electron states obtained from the variational method based on the variational functions we proposed are in excellent agreement with the results obtained from the exact diagonalization method we presented. A comparison between the results obtained from the variational functions proposed by us and Xiao is also verified. [ABSTRACT FROM AUTHOR]

The thermal dependence of the optical gain and threshold current density of GaInNAs/GaAs/AlGaAs quantum well (QW) lasers with the emission wavelength of 1.3 μm have been theoretically investigated. The optical gain is found to decrease with the increase of the temperature due to the hole leakage in the separate confinement heterostructure (SCH) region. The distribution of unconfined electrons in the SCH region is negligible while the distribution of unconfined holes in the SCH region plays an important role in the leakage process, reflecting the smaller bandgap discontinuity in the valence band than in the conduction band. The threshold current density increases with the increase of temperature, which is dominated by the monomolecular recombination process. Our calculated threshold current densities with temperatures are in agreement with the available experimental results. [ABSTRACT FROM AUTHOR]

The optical gain and radiative current density of GaInNAs/GaAs/AlGaAs separate confinement heterostructure quantum well (QW) lasers with an emission wavelength of 1.3 μm have been theoretically investigated. The effect of carrier leakage from the GaInNAs QW to the GaAs waveguide layer is studied, and its influence on the optical gain and radiative current density is identified. The hole filling caused by an injected carrier has a strong impact on the optical gain and radiative current density, while the effect of electron filling is negligible, reflecting the smaller band-gap discontinuity in the valence band than in the conduction band. Hole occupation in the waveguide layer decreases the optical gain, and increases the radiative and threshold current densities of the laser. Our calculated threshold current density (659.6 A/cm2) at T=300 K is in good agreement with the experimental value (650.9 A/cm2) reported in literature [R. Fehse et al., IEEE J. Sel. Top. Quantum Electron. 8, 801 (2002)]. [ABSTRACT FROM AUTHOR]

We have fabricated BiFeO3 thin film deposited on Pt/Ti/SiO2/Si substrates by the chemical solution deposition method. The effects of annealing temperature on the thin film structure, resistance switching (RS) properties, conduction mechanisms are investigated. It exhibits improved RS window with high ON/OFF ratio (∼ 104) for the sample annealed at 650 ∘ C. XPS characterization indicates that cation ratio of Fe 2 + /Fe 3 + is increased with increasing annealing temperature. Crystal lattice distortion generated by Fe 2 + cations, along with oxygen vacancies, commonly contribute to opening the RS window and the increment of conductive filaments. The film's conduction mechanisms under different annealing temperatures are fully discussed. The RS properties of this system can be effectively improved by increasing the annealing temperature, which is crucial prerequisite for future applications of BFO-based thin film device in resistance random access memory. The BiFeO3 thin film deposited on Pt/Ti/SiO2/Si substrates is fabricated by the CSD method was fabricated. The resistance switching properties of BFO thin film can be effectively improved by the different annealing temperature. Fe2+ cations along with oxygen vacancies, commonly contribute to opening the RS window and the increment of conductive filaments, are crucial to the enhanced RS properties. [ABSTRACT FROM AUTHOR]