饱和非线性超晶格中带隙孤子的特性研究

利用光谱重构法求解了聚焦饱和非线性超晶格半无穷带隙中的基模孤子，并研究了饱和程度和超晶格势场的相对强度对孤子的功率、稳定性的影响。研究结果表明：对于给定相对强度的超晶格势场，当饱和程度较低时，孤子在高功率区域不稳定，并且孤子的稳定范围随着饱和程度的增大而变宽；当饱和程度较高时，孤子功率随传播常数增大快速增大，但孤子是稳定的。此外，对于给定的低饱和程度，孤子的稳定范围随着超晶格中低频格子相对强度的增大而变宽。

PROPERTIES OF GAP SOLITONS IN SUPERLATTICES WITH SATURABLE NONLINEARITY

The fundamental solitons in the semi-infinite gap of superlattices under focusing saturable nonlinearity are solved by the spectral renormalization method. The effects of saturation degree and relative strength of superlattice potential on the power and stability of solitons are studied. The results show that for a fixed relative strength of superlattice potential, when the saturation degree is low, the solitons are unstable in the high-power region, and the stable range of the solitons becomes wider with the increase of the saturation degree. When the saturation degree is high, the soliton power grows dramatically with propagation constant, but the solitons are stable. Besides, for a given low saturation degree, the stable range of the solitons widens with an increase in the relative strength of low-frequency lattice in the superlattice.