激光与光电子学进展, 2016, 53 (9): 091901, 网络出版: 2016-09-14
无周期光学超晶格中耦合三次谐波转换效率的提高
Enhancement of the Coupled Third Harmonic Conversion Efficiency in Non-Periodic Optical Superlattice
非线性光学 耦合三次谐波 高转换效率 非线性共轭梯度算法 无周期光学超晶格 准相位匹配 nonlinear optics coupled third harmonic high conversion efficiency nonlinear conjugate-gradient method non-periodic optical superlattice quasi-phase matching
摘要
利用非线性共轭梯度算法(NCG)设计了无周期光学超晶格(NOS),在该结构中实现了高转换效率的耦合三次谐波(CTHG)。相对于传统的模拟退火算法(SA)所设计的非周期光学超晶格(AOS),无论单波长还是多波长的CTHG,利用NCG算法所设计的NOS结构可以得到更高的转换效率。这是因为在无周期光学超晶格结构中每层畴的宽度的选取是任意的,通过NCG算法对每层畴宽度进行优化,可以达到更好的准相位匹配(QPM)。计算了转换效率随光波传播距离的变化情况,结果表明转换效率随光波传播距离的增加而增大,这说明每层畴对转换效率的贡献是积极的,所设计的样品达到了准相位匹配。
Abstract
The high conversion efficiency of coupled third harmonic generation (CTHG) is achieved in the non-periodic optical superlattice (NOS) which is devised by the nonlinear conjugate-gradient (NCG) method. For either the single wavelength case or the multiple wavelengths case, the conversion efficiency of CTHG is higher in the NOS structure than that in the aperiodic optical supperlattice (AOS) which is devised by the traditional simulated annealing method. Since the thickness of each domain is arbitrary and further optimization can be done by using NCG method, it is easier to achieve the optimal quasi-phase matching (QPM) in the NOS structure. The variation of conversion efficiency as a function of the optical wave propagating distance is calculated, and the results show that the conversion efficiency increases with the increase of the optical wave propagating distance, which indicates that the contribution of every domain on CTHG process is positive, and that the optical QPM can be achieved in the NOS structure.
张丽娟, 赵丽明. 无周期光学超晶格中耦合三次谐波转换效率的提高[J]. 激光与光电子学进展, 2016, 53(9): 091901. Zhang Lijuan, Zhao Liming. Enhancement of the Coupled Third Harmonic Conversion Efficiency in Non-Periodic Optical Superlattice[J]. Laser & Optoelectronics Progress, 2016, 53(9): 091901.