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The long-term stability of InGaN photoanodes in liquid environments is an essential requirement for their use in photoelectrochemistry. In this paper, we investigate the relationships between the compositional changes at the surface of n-type InxGa1-xN (x similar to 0.10) and its photoelectrochemical stability in phosphate buffer solutions with pH 7.4 and 11.3. Surface analyses reveal that InGaN undergoes oxidation under photoelectrochemical operation conditions (i.e., under solar light illumination and constant bias of 0.5 V-RHE), forming a thin amorphous oxide layer having a pH dependent chemical composition. We found that the formed oxide is mainly composed of Ga-O bonds at pH 7.4, whereas at pH 11.3 the In-O bonds are dominant. The photoelectrical properties of InGaN photoanodes are intimately related to the chemical composition of their surface oxides. For instance, after the formation of the oxide layer (mainly Ga-O bonds) at pH 7.4, no photocurrent flow was observed, whereas the oxide layer (mainly In-O bonds) at pH 11.3 contributes to enhance the photocurrent, possibly because of its reported high photocatalytic activity. Once a critical oxide thickness was reached, especially at pH 7.4, no significant changes in the photoelectrical properties were observed for the rest of the test duration. This study provides new insights into the oxidation processes occurring at the InGaN/liquid interface, which can be exploited to improve InGaN stability and enhance photoanode performance for biosensing and water-splitting applications.

For GaAs we have determined \chi(xyz)((2))(-2omega; omega, omega)\ in second-harmonic generation experiments using two-photon energies between 2 and 5 eV. In addition to the E-1, E-1 + Delta(1), E-0', and E-2 critical-point bulk transitions of GaAs, a surprisingly strong surface transition at 3.35 eV was observed for natively oxidized GaAs(001) samples. A detailed comparison with theoretical predictions reveals that calculations that include many-particle effects at the level of the "scissors" approximation can describe the overall frequency dependence of the second-harmonic susceptibility reasonably well.

By applying fast sweeping of the laser wavelength at the headend station and a multi-passband optical filter at the antenna stations, multi-GHz signals can be distributed cost-effectively using GIPOF links in a wireless LAN. Data signal transparency and simple antenna stations are obtained. First simulations have shown the feasibility of the system concept.