Semiconductor laser is partially coherent beam, while the beam quality factor is based on fully coherent beam. The Wigner distribution function for partially coherent beam is used to analyze the semiconductor laser beam. The Wigner distribution function contains both spatial information and spatial frequency information in the phase space. A method for measuring the Wigner distribution function of semiconductor laser is reported. The intensity distribution of the beam caustics is measured by two focusing mirrors, and the Wigner distribution function of semiconductor laser is reconstructed. Based on the reconstructed Wigner distribution function, the light intensity of semiconductor laser is simulated. The simulated data are in good agreement with the experimental data. Through the properties of Wigner distribution function, the wavefront aberration and coherence of semiconductor laser are analyzed. The wavefront of semiconductor laser is symmetrically distributed around a point, and the wavefront on the left side of the laser diode array is larger than that on the right side. Due to the temperature difference of the laser chip, the coherence on both sides of the laser diode array is better than that in the middle of the laser diode array.
Based on the analysis of Talbot phase-locking theory of edge emitting semiconductor lasers, a method to obtain a single in-phase mode on a tapered laser chip is proposed. A phase-locked model with 1/2 Talbot spatial filter cavity for mode selection placed between 8 emitters on each facet is set up. Based on the mode coupling rate equation theory, the parallel coupling phase-locking conditions with different fill factors is analyzed. The results show that the stable parallel coupling phase lock can be achieved for 8 emitters with the pitch of 20 um, when the fill factor is set between 0.06 and 0.12, and the phase-locking time is about 3 ns. The supermode threshold gains are also calculated under different fill factors. In the phase-locked model, when the fill factor is approximately 0.1, the threshold gain difference between the in-phase mode and out-phase mode could reach the maximum, which is around 78cm-1 . Therefore, single in-phase mode output of this novel laser with Talbot cavity becomes more robust. The simulation analysis provides a reliable theoretical support for the preparation of a coherent array laser with a single in-phase mode output.
The band structure, density of states, optical properties, effective masses and loss function of AlxGa1−xAs and InyGa1−yAs were performed by the first-principles method within the local density approximation. The calculated direct band gap of the AlAs, Al0.5Ga0.5As, GaAs, In0.5Ga0.5As and InAs were 1.608 eV, 1.34eV, 1.02eV, 0.646eV and 0.316eV at G point, which were direct bandgap semiconductor materials. In addition, dielectric functions, the absorption function, refractive index, loss function and effective mass were analyzed in detail. The effective masses of AlxGa1−xAs and InyGa1−yAs were small, so they have high carrier mobility. These results make them to be promising candidates for future electronics.
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