High-efficiency, environment friendly, renewable energy-based methods of desalination represent attractive and potentially very powerful solutions to the long-standing problem of global water shortage. Many new laboratoryscale materials have been developed for photothermal desalination but the development of low-cost, easy-to-manufacture, and scalable materials and systems that can convert solar irradiation into exploitable thermal energy in this context is still a significant challenge. This paper presents work on a geopolymer-biomass mesoporous carbon composite (GBMCC) device with mesoporous and macroporous structures for harvesting solar energy, which is then used in a device to generate water vapor with high efficiency using negative pressure, wind-driven, steam generation. The GBMCC device gives water evaporation rates of 1.58 and 2.71 kg m −2 h −1 under 1 and 3 suns illumination, with the solar thermal conversion efficiency up to 84.95% and 67.6%, respectively. A remarkable, record high water vapor generation rate of 7.55 kg m −2 h −1 is achieved under 1 sun solar intensity at the wind speed of 3 m s −1 . This is a key step forward todays efficient, sustainable and economical production of clean water from seawater or common wastewater with free solar energy.

Using an electrically pumped multisection technique, we have directly measured the internal optical mode loss of semiconductor-laser structures containing 1, 3, 5, and 7 layers of uncoupled InGaAs quantum dots. The optical loss does not increase with the number of dot layers so higher net modal gain can be achieved by using multiple layers. The maximum modal gain obtained from the ground state increases with dot layer number from 10Ϯ4 cm Ϫ1 for a single layer to 49Ϯ4 cm Ϫ1 for the 7 layer sample, which is typical of the threshold gain requirement of a 350 m long device with uncoated facets.

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