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11 August 2011 Quasi-phase matching analysis of the terahertz generation in CdTe pumped by 1064nm ns laser
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The terahertz radiation from the crystal of Cadmium Telluride (CdTe) can be achieved in difference frequency generation (DFG) experiment of 1064 nm nanosecond laser for collinear configuration. For the isotropic crystal CdTe, the exact phase matching could not be fulfilled by the two NIR lasers. However, if the interaction length is smaller than the coherent length, quasi-phase matching could be achieved. In order to understand the property of the coherent length in CdTe, the property of the refractive index and the absorption coefficient at the THz region is analyzed by two kinds of transmission spectra: one from Terahertz Time-Domain Spectroscopy (TDS) and the other from Fourier Transform Infrared Spectrometer (FTIRS). From the transmission spectra of FTIRS, four absorption lines are detected: 2.1 Thz, 4.2 Thz, 7.4 Thz, and 8.6 Thz. Also additional two little absorption peaks occurred at 1.6 Thz and 1.8 Thz. This maybe explained by the phone mode LO-LA and LA-TA, respectively. Below 1.0 Thz, the absorption coefficient is small and constant (about 5cm-1). Based on the refractive index spectra of THz-TDS, the coherent length calculated increases linearly with the THz wavelength in the region of 200μm to 900μm, with its' value 3.6 mm at 300μm. Then interaction length can be long enough to satisfy the quasi-phase matching condition. A high power and compactable terahertz source can be obtained from CdTe under 1 Thz, which can be tuned continually and operated under room temperature.
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Jing Guo Huang, Bing Bing Wang, Jin Xing Lu, and Zhi Ming Huang "Quasi-phase matching analysis of the terahertz generation in CdTe pumped by 1064nm ns laser", Proc. SPIE 8195, International Symposium on Photoelectronic Detection and Imaging 2011: Terahertz Wave Technologies and Applications, 81951U (11 August 2011);

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