A novel material deposited by molecular beam epitaxy at low substrate temperatures using Ga and As4 beam fluxes has been used as the active layer for a high-speed photoconductive optoelectronic switch. The high-speed photoconductive performance of the material was assessed by fabricating two devices: an Auston switch and a photoconductive-gap switch with a coplanar transmission line. In a coplanar transmission line configuration, the speed of response is 1.6 ps (full width at half maximum) and the response is 10 to 100 times greater than that of conventional photoconductive switches. Since the material is compatible with GaAs discrete device and integrated circuit technologies, this photoconductive switch may find extensive applications for high-speed device and circuit testing.

After China launched its "Belt and Road" (BR) initiative, the international community became concerned that it may worsen the environmental performance of the BR countries. Due to a lack of data for empirical testing, this paper addresses this concern through an indirect method and draws the implications of the potential impacts of China's BR initiative. This method empirically examines the effects of trade integration and regional cooperation, two major functions of the BR initiative, on energy efficiency (EE) convergence, a concept that describes the catching up process of EE across countries. A sample of 89 countries was selected to analyse the process of EE convergence from 2000 to 2014. The results indicate that although the gaps in EE among countries around the world become larger after 2010, regional cooperation may lead to a convergence process. It also finds that trade integration has a positive influence on convergence across the countries, especially among middle-and low-income countries. The results suggest that the BR initiative, through its roles in trade integration and regional cooperation, may promote EE convergence among countries. This is a desirable environmental outcome. This research also provides policy implications for both China and the other BR countries.

Mid-infrared (MIR) (3-12 um) spectral imaging is a power analytical tool, but difficult in the back-reflectance mode for in-vivo diagnostics. Feasibility of MIR back-reflectance imaging is demonstrated using MIR semiconductor lasers. Transmittance through 500-microm thick films of water and blood showed a capability to resolve more than 6-OD signal dynamic range. Reflectance scanning imaging through a 150-microm thick film of blood showed negligible scattering effect, indicating the feasibility of optical coherent imaging. The result of coherent imaging of a plant leaf shows a MIR sub-surface image that would not be visible in white light. With two wavelengths, a similar result for a chicken skin subcutaneous tissue at different focal depths was obtained, showing blood vessels beneath a lipid layer. These results suggest that advanced multilaser wavelength systems in the fingerprint spectral region can be a useful tool for in-vivo spectral imaging in biomedical research and diagnostic applications.