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Zhongyang Li,Silei Wang,Mengtao Wang,Weishu Wang 한국광학회 2017 Current Optics and Photonics Vol.1 No.2
Terahertz (THz) generation by periodically-poled KTiOPO4 (PPKTP) with a quasi-phase-matching schemebased on cascaded difference frequency generation (DFG) processes is theoretically analyzed. The cascadedStokes interaction processes and the cascaded anti-Stokes interaction processes are investigated fromcoupled wave equations. THz intensities and quantum conversion efficiency are calculated. Compared withnon-cascaded DFG processes, THz intensities from 10-order cascaded DFG processes are increased to 5.53. The quantum conversion efficiency of 479.4% in cascaded processes, which exceeds the Manley-Rowelimit, can be realized.
Investigation of Stimulated Polariton Scattering from the B₁-symmetry Modes of the KNbO₃ Crystal
Zhongyang Li,Mengtao Wang,Silei Wang,Bin Yuan,Pibin Bing,Degang Xu,Jianquan Yao 한국광학회 2018 Current Optics and Photonics Vol.2 No.1
Stimulated polariton scattering from the B₁-symmetry modes of a KNbO₃ crystal to generate a terahertz wave (THz-wave) with a noncollinear phase-matching scheme is investigated. The frequency-tuning characteristics of the THz-wave by varying the phase-matching angle and pump wavelength are analyzed. The expression for the effective parametric gain length under the noncollinear phase-matching condition is deduced. Parametric gain and absorption characteristics of the THz-wave in KNbO₃ are theoretically simulated. The characteristics of KNbO₃ for a terahertz parametric oscillator (TPO) are compared to those of MgO:LiNbO₃. The analysis indicates that KNbO₃ is an excellent optical crystal for a TPO, to enhance the THz-wave output.
Zhongyang Li,Qudong Wang,Huaping Tang,Tianwen Liu,Chuan Lei,Haiyan Jiang,Wenjiang Ding 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.10
The variation of microstructure and mechanical properties along the cross section of squeeze cast Al-5Mg-3Zn-1Cu-1Sialloy is studied under both squeeze-cast and peak-aged condition (470 °C × 24 h + 125 °C × 24 h). For squeeze-cast alloy,along the depth direction, second dendrite arm space and the percentage of -Al increase significantly, while the volumefraction of T-Mg32(AlZnCu)49 and Mg2Siphase showed a dramatic decrease. The ultimate tensile strength of squeeze-castalloy slightly decreased from 357.04 MPa for the surface layer to 344.21 MPa for the central layer, yield strength droppedfrom 296.86 MPa to 241.03 MPa, but the elongation almost tripled from 1.42% to 3.78%. After peak aging, the ultimatetensile strength of surface layer and central layer reached 538.45 MPa and 504.03 MPa, yield strength reached 447.46 MPaand 442.65 MPa, and the elongation reached 5.23% and 3.97% respectively. Meanwhile the difference of ultimate tensilestrength and elongation was increased, but that of yield strength reduced after aging treatment. Precipitation strengtheningis the main strengthening mechanism while the improvement in ductility is due to the dissolution of T-Mg32(AlZnCu)49 andthe morphological change of eutectic Mg2Si.
Zhongyang Li,Bin Yuan,Silei Wang,Mengtao Wang,Pibin Bing 한국광학회 2018 Current Optics and Photonics Vol.2 No.3
Stimulated polariton scattering (SPS) from the A₁ transverse optical (TO) modes of BaTiO₃ bulk crystal generating a terahertz (THz) wave with the noncollinear phase-matching (NPM) condition is theoretically investigated. To our best knowledge, this is the first report on THz wave generation from BaTiO₃ bulk crystal via SPS. Phase-matching (PM) characteristics in the NPM configuration are analyzed. Effective parametric gain lengths for the Stokes and THz waves in the NPM configuration are calculated. The effective parametric gain coefficient and absorption coefficient of the THz wave in BaTiO₃ are theoretically simulated. The THz phonon flux densities generated via SPS in BaTiO₃ are theoretically calculated by solving the coupled wave equations under the NPM condition. The PM characteristics and THz-wave parametric gain characteristics in BaTiO₃ are compared to those in MgO:LiNbO₃. The results of the analysis indicate that BaTiO₃ is an attractive optical crystal for efficient THz wave generation via SPS.
Zhongyang Li,Bin Yuan,Silei Wang,Mengtao Wang,Pibin Bing 한국광학회 2018 Current Optics and Photonics Vol.2 No.2
Terahertz (THz) wave generation by periodically poled BaTiO₃ (PPBT) with a quasi-phase-matching (QPM) scheme based on cascaded difference-frequency generation (DFG) is theoretically analyzed. The cascaded DFG processes comprise cascaded Stokes and anti-Stokes processes. The calculated results indicate that the cascaded Stokes processes are stronger than the cascaded anti-Stokes processes. Compared to a noncascaded Stokes process, THz intensities from 20<SUP>th</SUP>-order cascaded Stokes processes increase by a factor of 30. THz waves with a maximum intensity of 0.37 MW/mm² can be generated by 20<SUP>th</SUP>-order cascaded DFG processes when the optical intensity is 10 MW/mm², corresponding to a quantum conversion efficiency of 1033%. The high quantum conversion efficiency of 1033% exceeds the Manley-Rowe limit, which indicates that PPBT is an excellent crystal for THz wave generation via cascaded DFG.
Zhongyang Li,Pibin Bing,Shengyuan Xu,Degang Xu,Jianquan Yao 한국광학회 2015 Current Optics and Photonics Vol.19 No.3
Terahertz (THz) wave generation from bulk and periodically poled LiTaO3 (PPLT) with a Cherenkovphase matching scheme is numerically investigated. It is shown that by using the crystal birefringenceof bulk LiTaO3 and a grating vector of PPLT, THz waves can be efficiently generated by differencefrequency generation (DFG) with a Cherenkov phase matching scheme. The frequency tuning characteristicsof the THz wave via varying wavelength of difference frequency waves, phase matching angle, polingperiod of PPLT and working temperature are theoretically analyzed. The parametric gain coefficient inthe low-loss limit and the absorption coefficient of the THz wave during the DFG process in the vicinityof polariton resonances are numerically analyzed. A THz wave can be efficiently generated by utilizingthe giant second order nonlinearities of LiTaO3 in the vicinity of polariton resonances
Zhongyang Li,Kai Zhong,Pibin Bing,Sheng Yuan,Degang Xu,Jianquan Yao 한국광학회 2016 Current Optics and Photonics Vol.20 No.1
Terahertz (THz) generation by a GaP ridge waveguide with a collinear modal phase-matching schemebased on cascaded difference frequency generation (DFG) processes is theoretically analyzed. The cascadedStokes interaction processes and the cascaded anti-Stokes interaction processes are investigated fromcoupled wave equations. THz intensities and quantum conversion efficiency are calculated. Compared withnon-cascaded DFG processes, THz intensities from 11-order cascaded DFG processes are increased to 5.48. The quantum conversion efficiency of 177.9% in cascaded processes can be realized, exceeding theManley-Rowe limit.
Frequency Tuning Characteristics of a THz-wave Parametric Oscillator
Zhongyang Li,Pibin Bing,Degang Xu,Jianquan Yao 한국광학회 2013 Current Optics and Photonics Vol.17 No.1
Frequency tuning characteristics of a THz-wave by varying phase-matching angle and pump wavelength in a noncollinear phase-matching THz-wave parametric oscillator (TPO) are analyzed. A novel scheme to realize the tuning of a THz-wave by moving the cavity mirror forwards and backwards is proposed in a noncollinear phase-matching TPO. The parametric gain coefficients of the THz-wave in a LiNbO3crystal are explored under different working temperatures. The relationship between the poling period of periodically poled LiNbO3 (PPLN) and the THz-wave frequency under the condition of a quasi-phasematching configuration is deduced. Such analyses have an impact on the experiments of the TPO.