Abstract-Terahertz waves generation using the isomorphs of PPKTP crystal: a theoretical investigation

 

Guo-Qun Chen, Hong-Yang Zhao, Shun Wang, Xiangying Hao, Hai-Wei Du, and Rui-Bo Jin

Schematic diagram of cascaded difference frequency. The propagation directions of the pump, the signal and THz wave are along the x axis, while their polarization directions are along the z axis.

https://www.osapublishing.org/osac/fulltext.cfm?uri=osac-4-8-2330&id=454030

Highly efficient terahertz (THz) wave sources based on the difference frequency generation (DFG) process in nonlinear optical crystals plays an important role for the applications of THz waves. In order to find more novel nonlinear crystals, here, we theoretically investigate the generation of THz waves using the isomorphs of periodically poled KTiOPO4 (PPKTP), including periodically poled RTP, KTA, RTA and CTA. By solving the cascaded difference frequency coupled wave equations, it is found that the intensities of the THz wave generated from the cascaded difference frequency processes are improved by 5.27, 2.87, 2.82, 3.03, and 2.76 times from the non-cascaded cases for KTP, RTP, KTA, RTA and CTA, respectively. The effects of the crystal absorption, the phase mismatch, and the pump intensity are also analyzed in detail. This study might help to provide a stronger THz radiation source based on nonlinear crystals.

© 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Abstract-Calibration of the field strength of broadband terahertz radiation in air coherent detection technique

Journal of Applied Physics

Hai-Wei Du, Fu Tang, Dong-Yu Zhang, Wang Sheng, Jing-Yi Mao,

https://aip.scitation.org/doi/10.1063/1.5039827

In the air coherent detection of the terahertz (THz) technique, a high voltage signal with a square waveform offers a modulated biased field over the air sensor. In this technique, a temporal THz waveform can be obtained routinely. However, its field strength has to be calibrated separately by other techniques. In this paper, we propose a method to calibrate the field strength of the THz pulse by means of applying a positive square wave instead of an alternating square wave as the modulated biased field. In this method, the ratio of the THz signal to the background signal is used for the calibration of the field strength of the THz pulse. Using this method, both the waveform and the electric field strength of the THz pulse can be easily obtained.

Abstract-THz generation from optical rectification tilted-pulse-front pumping scheme with laser pulse focused to a line

Hai-Wei Du, Hiromichi Hoshina, Chiko Otani

RIKEN Ctr. for Advanced Photonics (Japan)

Proc. SPIE 9671, AOPC 2015: Advances in Laser Technology and Applications, 96710M (October 15, 2015); doi:10.1117/12.2199229

http://proceedings.spiedigitallibrary.org/proceeding.aspx?articleid=2464111

In this study, we investigate THz pulses generated from optical rectification with tilted-pulse-front pumping scheme in which the laser beam is focused to a line in a stoichiometric lithium niobate (sLN) crystal. A cylindrical lens and a common lens are used to focus the pump laser beam to a line. The power law of THz pulse generation and the redshift induced from the sLN crystal are measured. The spectral shapes of the laser pulse are changed by inserting a filter into the pump laser beam, causing the THz radiation to change. The filter is a metal wire with 2 mm diameter. Experimental results show that this method can change the generated THz time waveforms but not their spectra. Such method offers a simple means to change and manipulate THz field generated from optical rectification with tiled-pulse-front pumping scheme.
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