Hahn Choloong, Song Seok Ho, Oh Cha Hwan, Berini Pierre
Opt Express. 2015 Jul 27;23(15):19922-31. doi: 10.1364/OE.23.019922.
Single-mode distributed feedback laser structures and parity-time symmetry broken grating structures based on dielectric-loaded long-range surface plasmon polariton waveguides are proposed. The structures comprise a thin Ag stripe on an active polymer bottom cladding with an active polymer ridge. The active polymer assumed is PMMA doped with IR140 dye providing optical gain at near infrared wavelengths. Cutoff top ridge dimensions (thickness and width) are calculated using a finite element method and selected to guarantee single-mode operation of the laser. Several parameters such as the threshold number of periods and the lasing wavelength are determined using the transfer matrix method. A related structure based on two pairs of waveguides of two widths, which have the same imaginary part but different real part of effective index, arranged within one grating period, is proposed as an active grating operating at the threshold for parity-time symmetry breaking (i.e., operating at an exceptional point). Such "exceptional point" gratings produce ideal reflectance asymmetry as demonstrated via transfer matrix computations.
提出了基于介质加载远程表面等离激元极化子波导的单模分布反馈激光结构和奇偶时间对称破缺光栅结构。这些结构包括在有源聚合物底部包层上的薄银条带以及有源聚合物脊。假设的有源聚合物是掺杂有IR140染料的聚甲基丙烯酸甲酯，其在近红外波长下提供光学增益。使用有限元方法计算截止顶脊尺寸（厚度和宽度），并进行选择以确保激光器的单模运行。使用传输矩阵方法确定诸如阈值周期数和激射波长等几个参数。提出了一种基于两对不同宽度波导的相关结构，这两对波导在一个光栅周期内排列，具有相同的有效折射率虚部但实部不同，作为在奇偶时间对称破缺阈值下工作的有源光栅（即在例外点工作）。通过传输矩阵计算表明，这种“例外点”光栅产生理想的反射不对称性。
