A high power and good beam quality InGaAs/GaAs quantum well semiconductor disk laser at 1 015 nm wavelength is reported. The semiconductor wafer is grown in reverse order: substrate is on the window side and the distributed Bragg reflector is the last grown epilayer. Then the wafer is up-side-down and capillary bonded to a SiC heatsink, and the substrate is chemically etched. Because the total thickness of the substrate-removed structure is less than 10 µm, the thermal management of the laser is significantly improved, and the maximum output power over 0.6 W is obtained using a 3% output coupler and 3.2 W incident pump power. The M 2 factors of 1.02 and 1.01 indicate a near-diffraction-limited beam quality. To further reveal the characteristics of this substrate-etched structure on the thermal management, the heat flux and the temperature distribution of the gain wafer are numerically analyzed, and the corresponding results are discussed.
Keeping deposition temperature and oxygen pressure constant at 300°C and 4.0×10-2Pa, respectively, deposition of ZnO thin films with c-axis oriented (002) hexagonal wurtzite crystal structure was achieved by pulsed filtered cathodic vacuum arc deposition (PFCVAD) system at various negative substrate bias on Si(100). The surface morphology was characterized using AFM, and crystallographic structure was studied by means of X-ray diffraction. Based on the biaxial strain model, Strain properties of the ZnO films were investigated by calculation from XRD data. The calculated results revealed that the as-deposited ZnO films exhibited only tensile stress and the tensile stress increased with the elevation of the negative substrate bias. Occurrence of the tensile stress is suggested to be the result of relatively high deposition temperature and the improved deposition rate by elevating the negative substrate bias. It provides a potential method to control the intrinsic stress in the ZnO films by modulation of deposition temperature and the negative substrate bias of PFCVAD system.
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