High-brightness wavelength-beam-combined diode laser stacks using a volume Bragg grating (VBG)
Using VBG-stabilized wavelength beam combining of 3-bar diode laser stack, we demonstrate 89.5 W CW with beam quality M2 ~ 26 in the slow-axis and M2~21 in the fast-axis. The beam combining efficiency is 75%.
Wavelength stabilization and spectrum narrowing of high-power multimode laser diodes and arrays by use of volume Bragg gratings.
Spectral line narrowing (by a factor of 8) and stabilization of the emission wavelength (by a factor of 30) of multimode high-power laser diodes and arrays is demonstrated by use of volume Bragg gratings fabricated in high-stability inorganic photorefractive glasses. Applications include stabilization of pump laser diodes and arrays for solid-state lasers and metal-vapor lasers, spin hyperpolarization of noble gases used in medical imaging, and others.
The contribution of charcoal production to rural livelihoods in a semi-arid area in Kenya
Forest incomes in the form of both timber and non-timber forest products are an important source of livelihood for many communities in Africa. A major forest resource is charcoal, which contributes to the livelihoods of millions across the region. While incomes from charcoal are used to meet a wide spectrum of needs within rural livelihoods, the role of charcoal production on livelihoods of small-scale producers is not well understood. Therefore, we provide an example on the importance of charcoal on livelihoods in an agropastoralist community in a semi-arid region in Kenya. Based on a household questionnaire targeting 150 charcoal and 150 non-charcoal makers, as well as focus group discussions, we assessed the determinants for participation in charcoal production and developed a household typology based on charcoal income dependence. We also determined the role of charcoal in income equalization and poverty reduction. Our study shows that charcoal contributes about 20% of the household income in the study area. Gender, land size and the number of food-scarce months are the key determinants of participation in charcoal production. Based on the poverty analysis, we conclude that even though charcoal income does not lift the producers out of poverty, it can mitigate the impacts of poverty by reducing the poverty gap and poverty severity. Based on our findings, we recommend a multipronged approach to address sustainable rural livelihoods including a more explicit acknowledgement of charcoal production as a source of rural income. We also recommend broadening of the local livelihood base and a more active management of the woodland to ensure the sustainability of the income.