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A novel reflected terahertz-emission microscopy is proposed and developed for improving the spatial resolution of THz imaging. When attaching a bow-tie antenna directly onto a thin generation crystal, the reflected THz waves can be collected and detected by a photoconductive antenna, and the spatial resolution is decided by the diameter of focused pump beam. In this way, the detected resolution can be largely improved and tunable. The configuration and characteristics of this microscopy are described in detail.  相似文献
2.
In a novel generation and detection configuration of terahertz (THz) radiation, we investigate experimentally and numerically the properties of sub-cycle THz pulses in the near field. It is found that the sub-cycle THz pulses experience significant spectral and temporal deformation in the near-field zone. The variations of both the pulse waveform and spectral distribution of the THz electric field are clearly observed in our experiments when the spot size of source is changed. Numerical simulations based on Gaussian distribution are performed to explain the details of the data and lead to an excellent agreement with the experimental results.  相似文献
3.
THz emission spectroscopy is used to study the generation mechanism dependent behaviour of terahertz (THz) electromagnetic waves from the GaAs crystal under excitation by 40Ohm and 800hm femtosecond (fs) pulses, respectively. The wavelength dependence of the emission spectrum under two types of THz generation mechanis msis analysed. Under the optical rectification mechanism, a slight enhancement of the spectral amplitude in the high-frequency regime is observed in a GaAs(l10) crystal by the excitation of a 400-nm optical pulse compared with that of 800nm. Whereas an obvious red shift of the amplitude spectrum occurs in the GaAs(100) sample under the transient photoconduction mechanism. These phenomena are explained in detail by the duration of the optical pump pulse and the band structure of GaAs, respectively.  相似文献
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