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We report on a single-frequency semiconductor disk laser which generates 23.6 W output power in continuous wave operation, at a wavelength of 1013 nm. The high output power is a result of optimizing the chip design, thermal management and the cavity configuration. By applying passive stabilization techniques, the free-running linewidth is measured to be 407 kHz for a sampling time of 1 ms, while undercutting 100 kHz in the microsecond domain.

The design and experimental realization of a type-II “W”-multiple quantum well heterostructure for emission in the λ > 1.2 μm range is presented. The experimental photoluminescence spectra for different excitation intensities are analyzed using microscopic quantum theory. On the basis of the good theory–experiment agreement, the gain properties of the system are computed using the semiconductor Bloch equations. Gain values comparable to those of type-I systems are obtained.

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The formation of ultrathin copper oxide layers on an Au(111) surface is explored with scanning tunneling microscopy and density functional theory. Depending on the thermal treatment of as-grown Cu-O samples, a variety of thin-film morphologies is observed. Whereas 1D oxide stripes with Au[112[combining macron]] and Au[11[combining macron]0] orientation emerge at 450 and 550 K annealing, respectively, a planar (2 × 2) Cu-O network with specific domain structure develops at higher temperature. The latter is ascribed to a CuO honeycomb lattice with oxygen ions alternatingly located in surface and interface positions. Strain minimization and a thermodynamic preference for Cu-rich edges lead to the formation of structurally well-defined boundaries, delimiting either triangular, elongated or stripe-like CuO domains. The low-temperature phases compirse complex arrangements of hexagonal and square Cu-O units, similar to those found in CuO(111) and (100) surfaces, respectively. The transitions between different thin-film phases are driven by Cu dissolution in the gold crystal and O evaporation and therefore accompanied by a thinning of the oxide layer with increasing temperature.