The generation transmission, and detection of extremely rapid electromagnetic pulses have been achieved using fast photoconducting materials as time-varying Hertzian dipoles. This approach, which has a measured time response of 1.6 ps, overcomes many of the limitations imposed by transmission line structures, and due to its jitter-free behavior and open geometry is ideally suited for transient electromagnetic measurements of materials.

Photoconducting antennas have been demonstrated which are capable of generating and coherently detecting subpicosecond electrical pulses. These antennas, when illuminated with femtosecond optical pulses, radiate electrical pulses which have frequency spectra that extend from < 100 GHz to > 2 THz. Microscopic dipoles measuring 50, 100, and 200 pm have been fabricated and tested. Integrated photoconductors of radiation-damaged silicon-on-sapphire were used both for impulsive current excitation of the transmitting antennas as well as for gating the receiving antennas.

We have generated electromagnetic beams from a variety of semiconductors. When a bare semiconductor wafer was illuminated by femtosecond optical pulses, electromagnetic waves radiate from the surface and form collinear diffraction-limited electromagnetic beams in the inward and outward directions. The amplitude and phase of the radiated field depend on carrier mobility, the strength and polarity of the static internal field at the semiconductor surface.

No abstract

An earth-isolated optically coupled wideband high voltage probe powered by ambient light Rev. Sci. Instrum. 83, 104703 (2012) Reduction in subsidy for solar power as distributed electricity generation in Indian future competitive power market J. Renewable Sustainable Energy 4, 053120 (2012) Optimized working conditions for a thermoelectric generator as a topping cycle for gas turbines J. Appl. Phys. 112, 073515 (2012) Determination of salinity gradient power potential in Québec, Canada J. Renewable Sustainable Energy 4, 053113 (2012) Case study: Simulation and optimization of photovoltaic-wind-battery hybrid energy system in Taleghan-Iran using homer software J. Renewable Sustainable Energy 4, 053111 (2012) Additional information on Appl. Phys. Lett.

The basic concepts and preliminary applications of optically induced electromagnetic radiation from semiconductor surfaces and interfaces by using femtosecond optics are discussed. This submillimeter-wave radiation provides a novel optoelectronic technique to study semiconductor electronic surface and interface properties with a contactless approach. The amplitude and phase of the electromagnetic radiation from the semiconductor surfaces depend on carrier mobility, impurity doping concentration, and strength and polarity of the static internal field. A large selection of bulk, epitaxial layer and superlattice samples from III-V, II-VI and group-IV semiconductors has been tested. The orientation and strength of the static built-in fields of a wide range of semiconductor surfaces, such as surface depletion, metal/semiconductor Schottky, p-n junction and strain-induced piezoelectric fields, can be determined and estimated.

No abstract

No abstract