Liu Kefei, Zhong Kai, Yao Jianquan. Research Progress on Random Quasi-Phase Matching in Polycrystalline Materials[J]. Laser & Optoelectronics Progress, 2020, 57(21): 210001
- Laser & Optoelectronics Progress
- Vol. 57, Issue 21, 210001 (2020)
Fig. 1. Schematic of one-dimensional aperiodic materials. (a) Chirped crystal; (b) quasi-periodic crystal
![SHG in two-dimensional random SBN material. (a) Schematic; (b) experimental photograph (arrow indicates direction of fundamental beam)[20]](/richHtml/lop/2020/57/21/210001/img_2.jpg)
Fig. 2. SHG in two-dimensional random SBN material. (a) Schematic; (b) experimental photograph (arrow indicates direction of fundamental beam)[20]
![Spectral broadening of incident femtosecond pulse at 2.4 μm central wavelength in 5-mm-long polycrystalline ZnSe via RQPM frequency mixing[26]](/Images/icon/loading.gif){kind=icon}
Fig. 3. Spectral broadening of incident femtosecond pulse at 2.4 μm central wavelength in 5-mm-long polycrystalline ZnSe via RQPM frequency mixing[26]
Fig. 4. Harmonic and supercontinuum generation in polycrystalline Cr∶ZnS femtosecond laser. (a) 1st to 4th harmonic of fundamental beam; (b) supercontinuum spanning from 1.8 μm to 4.5 μm[28]
Fig. 5. OPO based on polycrystalline ZnSe. (a)Schematic of device with photo of ZnSe placed at the Brewster angle shown in bottom right; (b) broadband output spectrum spanning from 3 μm to 7.5 μm; (c) cavity length detuning[10]
Fig. 6. Schematic of laser beam with certain cross section passing through polycrystalline material. (a) Main view; (b) side view
Fig. 7. Schematic of random rotation transformation between reference coordinate and crystal coordinate[38]
Fig. 8. Effective nonlinear coefficient distribution of crystal grains after random rotation of one million times. (a) SHG with polarization parallel to that of fundamental beam; (b) SHG with polarization perpendicular to that of fundamental beam[10]
Fig. 9. Statistical result of SHG power of polycrystalline nSe with different lengths[10]
Fig. 10. Grain-size distributions of ZnSe under different treatment methods. (a) Original CVD ZnSe; (b) treatment in 850 ℃ Se vapor for 12 h; (c) treatment in 850 ℃ Zn vapor for 168 h; (c) treatment in 850 ℃ vacuum for 168 h[42]
Fig. 11. (Left) Polycrystalline material generated by Neper and (right) its meshed morphology
Fig. 12. Statistical properties of grains generated by Neper software. (a) Grain size; (b) sphericity
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