Abstract-Enhancement of Intracavity-Pumped Terahertz Parametric Oscillator Power by Adopting Diode-Side Pumped Configuration Based on KTiOPO4 Crystal

Feilong Gao, Xingyu Zhang ,Zhenhua Cong,Zhaojun Liu,Xiaohan Chen,Zengguang Qin,Peng Wang,Jinjin Xu,Zecheng Wang, Na Ming

 https://www.mdpi.com/2073-4352/9/12/666/htm

In this paper, a KTiOPO4 (KTP) crystal is used as the nonlinear medium in an intracavity-pumped terahertz parametric oscillator (TPO) based on stimulated polariton scattering (SPS). Almost all the reported intracavity SPS sources adopt the diode-end pumped configuration, and the THz output power is limited by the serious thermal effect and small fundamental beam size. For improving the THz output power, we propose diode-side pumping for the laser medium to get a higher fundamental power and a larger fundamental beam size. A convex–plane fundamental laser resonator is used to further offset the thermal effect and increase the fundamental beam size. The THz frequency of the intracavity-pumped KTP terahertz parametric oscillator can be discontinuously tuned from 3.19 THz to 5.94 THz with three gaps. The fundamental beam diameter in the KTP crystal is about 1.3 mm. The maximum average THz power is 166 μW at 5.74 THz under a pulse repetition frequency (PRF) of 6 kHz and a diode pump power of 98 W. By means of the diode-side pumped configuration, the maximum THz output power is more than two-fold higher compared to the diode-end pumped configuration reported using the KTP crystal.

Abstract-Energy scaling of terahertz-wave parametric sources

Energy scaling of terahertz-wave parametric sources Guanqi Tang, Zhenhua Cong, Zengguang Qin, Xingyu Zhang, Weitao Wang, Dong Wu, Ning Li, Qiang Fu, Qingming Lu, and Shaojun Zhang  »View Author Affiliations

http://www.opticsinfobase.org/oe/abstract.cfm?uri=oe-23-4-4144

Optics Express, Vol. 23, Issue 4, pp. 4144-4152 (2015)
http://dx.doi.org/10.1364/OE.23.004144

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Terahertz-wave parametric oscillators (TPOs) have advantages of room temperature operation, wide tunable range, narrow line-width, good coherence. They have also disadvantage of small pulse energy. In this paper, several factors preventing TPOs from generating high-energy THz pulses and the corresponding solutions are analyzed. A scheme to generate high-energy THz pulses by using the combination of a TPO and a Stokes-pulse-injected terahertz-wave parametric generator (spi-TPG) is proposed and demonstrated. A TPO is used as a source to generate a seed pulse for the surface-emitted spi-TPG. The time delay between the pump and Stokes pulses is adjusted to guarantee they have good temporal overlap. The pump pulses have a large pulse energy and a large beam size. The Stokes beam is enlarged to make its size be larger than the pump beam size to have a large effective interaction volume. The experimental results show that the generated THz pulse energy from the spi-TPG is 1.8 times as large as that obtained from the TPO for the same pumping pulse energy density of 0.90 J/cm² and the same pumping beam size of 3.0 mm. When the pumping beam sizes are 5.0 and 7.0 mm, the enhancement times are 3.7 and 7.5, respectively. The spi-TPG here is similar to a difference frequency generator; it can also be used as a Stokes pulse amplifier.

© 2015 Optical Society of America

Abstract-Terahertz parametric oscillator based on KTiOPO4 crystal

Weitao Wang, Zhenhua Cong, Xiaohan Chen, Xingyu Zhang, Zengguang Qin, Guanqi Tang, Ning Li, Cong Wang, and Qingming Lu  »View Author Affiliations

Optics Letters, Vol. 39, Issue 13, pp. 3706-3709 (2014)
http://dx.doi.org/10.1364/OL.39.003706

https://www.blogger.com/blogger.g?blogID=124073320791841682&pli=1#editor/target=post;postID=8620925169788540846

KTiOPO4 (KTP) crystal is used as the nonlinear medium in a surface-emitted terahertz-wave parametric oscillator for the first time. The oscillating Stokes beam propagates along the x axis of the KTP crystal, the pumping beam propagates with a small incident angle θext to the x axis, and the polarizations of the pumping beam, the Stokes beam, and the THz wave are along the z axis. When θext is changed from 1.250° to 6.000°, the THz wave is intermittently tuned from 3.17 to 3.44 THz, from 4.19 to 5.19 THz, and from 5.55 to 6.13 THz. The maximum output of the THz wave is 336 nJ, obtained at 5.72 THz with a pumping energy of 80 mJ. The two frequency gaps, from 3.44 to 4.19 THz and from 5.19 to 5.55 THz, are located in the vicinities of the A1 modes of 134 and 178.7  cm−1, which are strongly infrared absorbing.

© 2014 Optical Society of America