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InAs/GaAs quantum dot (QD) laser monolithically grown on silicon is one of the potential approaches to realizing silicon-based light sources. However, the mismatch between GaAs and Si generates a high density of threading dislocations (TDs) and antiphase boundaries (APBs), which trap carriers and adversely affect device performance. In this paper, we present a simple method to reduce the threading dislocation density (TDD) merely through GaAs buffer, eliminating the intricate dislocation filter layers (DFLs) as well as any intermediate buffer layers whose compositions are different from the target GaAs. An APB-free epitaxial 2.5 µm GaAs film was grown on exact Si (001) by metalorganic chemical vapor deposition (MOCVD) with a TDD of 9.4 × 106 cm−2. InAs/GaAs QDs with a density of 5.2 × 1010 cm−2 were grown on this GaAs/Si (001) virtual substrate by molecular beam epitaxy (MBE) system. The fabricated QD laser has achieved a single facet room temperature continuous-wave output power of 138 mW with a threshold current density of 397 A/cm2 and a lasing wavelength of 1306 nm. In this work, we propose a simplified method to fabricate high-power QD lasers, which is expected to promote the application of photonic integrated circuits.

Vertical Cavity Surface Emitting Laser (VCSELs) as the ideal light source for rubidium (Rb) and cesium (Cs) atomic clocks is analyzed for its mode and polarization control. We fabricated three kinds of shapes: triangular, elliptic and circular oxidation aperture which also has different sizes. We formed 3 different shape oxide apertures by wet-oxidation with 36-39μm circular mesa. Our results show that triangular oxidized-VCSELs has the advantages of mode and polarization selection over elliptic and circular oxide aperture. When triangular oxide-confined VCSELs emit in single mode, the measured Side Mode Suppression Ratio (SMSR) is larger than 20 dB and Orthogonal Polarization Suppression Ratio achieves 10 dB. Resonant blueshift of VCSELs with triangular and elliptic aperture is observed with the decrease of aperture size.

Dual-wavelength laser sources have important applications in the interferometry and the nonlinear-frequency-conversion generated mid-infrared or terahertz-band coherent radiation. Vertical-external-cavity surface-emitting lasers own outstanding advantages such as high output power, good beam quality and flexible emission wavelength, which make them very suitable for dual-wavelength running. In this paper, we employ a collinear Y-type cavity to produce a dual-wavelength laser. There are two semiconductor gain chips in the resonant cavity, one has an active region of In_0.185Ga_0.815As/GaAs strained multiple quantum wells and a designed wavelength of 960 nm, and the other has an active region of In_0.26Ga_0.74As/GaAsP_0.02 strained multiple quantum wells and a target wavelength of 1080 nm. The peak wavelength of the photoluminescence of chip 1 is 950 nm, which is 10 nm shorter than the designed wavelength under weak pump, and the peak wavelength of the photoluminescence of chip 2 is 1094 nm, which is 14 nm longer than the target wavelength under low pump. When the pump power is increased, the peak wavelengths of the photoluminescence of two gain chips are both red-shifted. The oscillating laser wavelengths are centered at 953 nm and 1100 nm, the corresponding full width at half maximum (FWHM) values of the laser spectra are 1.1 nm and 2.7 nm, respectively. The wavelength spacing of the dual-wavelength is 147 nm, and the related mid-infrared coherent radiation is about 7.1 μm on the assumption that the dual-wavelength laser is used for difference frequency generation. When the absorbed pump power of each gain chip is 5.8 W, the total output power of the dual-wavelength laser reaches 293 mW at room temperature.

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