Parity-time对称性对电注入半导体激光器的模式控制

Mode control of electrically injected semiconductor laser with parity-time symmetry

非厄米的描述对于开放系统有重要意义,满足parity-time对称性的哈密顿量,其参数在一定范围内可以使能量具有实的本征值.本文通过模拟,研究了损耗大小以及结构对称性对条形波导中的parity-time对称性的影响,并通过实验发现了电注入条件下由parity-time对称破缺导致的脊条波导模式间隔加倍、模式数减半的现象.

The non-Hermitian description is of great significance for open systems,and the Hamiltonian which satisfies parity-time symmetry can make the energy have real eigenvalue within a certain range.The properties of parity-time symmetry have bright application prospects in optical systems.For semiconductor lasers,the parity-time symmetry can be constructed by adjusting the level of electrical injection to help achieve better mode control.Electric injection is easier to realize than optical pump when the device size is small and the structure is complex.Therefore,we hope to analyze the characteristics of the laser that satisfies the parity-time symmetry condition under the condition of electric injection.In this paper,we simulate the effects of different set loss values on parity-time symmetry.It is found that with the increase of set loss value,the imaginary part of the refractive index of the gain cavity corresponding to the parity-time symmetry breaking point so-called exceptional point will decrease,and the imaginary part of the characteristic frequency corresponding to the exceptional point will also decrease.We also simulate the effect of structural size ratio of gain region and loss region on parity-time symmetry.On condition that the total cavity length and the imaginary part of the refractive index of the loss region remain unchanged,as the gain cavity becomes longer and the loss cavity becomes shorter,the imaginary part of the refractive index of the gain cavity corresponding to the exceptional point will increase,and the imaginary part of the characteristic frequency corresponding to the exceptional point will also increase.And we qualitatively explain the above phenomenon through the coupled mode equations.Through experiments,metal organic chemical vapor deposition(MOCVD)and standard lithography techniques are used to fabricate asymmetric ridge lasers.Under thermoelectric cooler(TEC)refrigeration and by controlling the injection level of the gain area,the doubled mode spacing and halved mode number of ridge waveguide are found for the first time due to the parity-time symmetry breaking under the condition of electric injection.We believe that the study of parity-time symmetry in ridge laser under the condition of electric injection will be of great help in implementing the mode control.