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Articles you may be interested inUltrafast time-domain spectroscopy based on high-speed asynchronous optical sampling Rev. Sci. Instrum. 78, 035107 (2007);Free-carrier Faraday ellipticity and Faraday rotation are measured for a moderately doped n-type silicon wafer with the resistivity of 1.1 ⍀ cm under magnetic fields of ±3 T using the terahertz time-domain spectroscopy. From the experimental data, we obtain the time evolution of the electric-field vector of the terahertz radiation pulses. When the magnetic field is applied to the sample, the transmitted radiation has an elliptic polarization with its major axis rotated from the polarization direction of the incident radiation ͑Faraday effect͒. The Faraday ellipticity and Faraday rotation angle are obtained for the directly transmitted pulse ͑first terahertz pulse͒ and the pulse reflected twice at the sample surfaces ͑second terahertz pulse͒ separately. They are compared with the calculations using the Drude model. A slight deviation is observed between the experimental and calculated Faraday ellipticities and Faraday rotation angles probably due to the energy dependence of the carrier scattering time.

The excitation fluence and magnetic field dependence of terahertz (THz) radiation power from InAs is investigated. At low excitation fluence, an enhancement of the THz-radiation power is observed independent of the magnetic-field direction. As the excitation fluence is increased, a crossover of the terahertz radiation mechanism is observed. At excitation fluence above this crossover, the radiation power is either enhanced or reduced depending on the magnetic-field direction. These results are explained by considering the different THz-radiation mechanisms from the InAs surface with or without photoexcited carrier screening.

Terahertz (THz) radiation generated from photoconductive antenna fabricated on a single crystal zinc oxide (ZnO) is presented. The THz-radiation power is saturated at bias voltages above 800V∕cm and the obtained spectrum extends up to 1 THz. Moreover, ZnO is found to be highly transparent in the visible, near-infrared, mid-infrared and THz frequency regions. The results depicted here will categorically unravel the prospects of using ZnO as a material for integrated active optics.

The design of fluoride-based optical devices for deep ultraviolet applications is discussed. Variations in the band-gap energy and band structure with respect to composition are investigated for Li(1−x)KxBa(1−y)MgyF3 perovskites. The band-gap energy, lattice constant, and band structure of perovskitelike fluorides are estimated based on ab initio calculations within the local-density approximation. The lattice-matched double heterostructure with direct band-gap compounds (Li(1−x)KxBa(1−y)MgyF3 on either LiBaF3 or KMgF3 substrates) is promising for fabrication.