Single-Mode Lasers and Parity-Time Symmetric Structures Based on Dielectric-Loaded Long-Range Surface Plasmon Polariton Waveguides

Choloong Hahn Department of Physics, Hanyang University, Seoul, South Korea Seok Ho Song Department of Physics, Hanyang University, Seoul, South Korea Pierre Berini School of Electrical Engineering and Computer Science, University of Ottawa, Ottawa, Ontario, Canada Department of Physics, University of Ottawa, Ottawa, Ontario, Canada Centre for Research in Photonics, University of Ottawa, Ottawa, Ontario, Canada

Long-range surface plasmon polaritons (LRSPPs) can be guided in a dielectric-metal-dielectric slab structure. However, the slab mode is not confined in the lateral direction, so by reducing the width of the top dielectric material, LRSPPs can be confined laterally - such a structure is referred to as the dielectric-loaded LRSPP waveguide [1]. Here we propose a novel single-mode distributed feedback (DFB) laser structure and a parity-time symmetric (PTS) structure employing the dielectric-loaded LRSPP waveguide. A schematic of our DFB structure is shown in Fig. (a): the purple region is IR140 doped PMMA and the gray region is a Ag thin film. IR140 doped PMMA provides optical gain in the 850 – 900 nm wavelength range [2]. The effective index of a dielectric-loaded LRSPP waveguide as a function of the top ridge width is shown in Fig. (c). In the calculations, 25 nm of Ag and a top layer 950 nm thick were assumed. The structure can be single long-range moded by controlling the width and thickness of the top ridge. There are some large dips in the imaginary index part of neff, as observed in the bottom of Fig. (c), due to changes in the supermode character as different constituent SPP modes couple in and out of the supermode. However, several candidate widths can be selected to form a DFB structure which has low loss and a well-defined mode profile. Fig, (b) shows the mode profile for w = 4.3 um, one of the candidate widths. We can also find a pair of widths which have the same imaginary index but different real index, and by selecting four such widths, it is possible to form a PTS grating structure which has a spatially non-reciprocal reflectance. Design details of these active plasmonic structures will be presented along with preliminary experimental results.

[1] T. Holmgaard and S. Bozhevolnyi, “Theoretical analysis of dielectric-loaded surface plasmon-polariton waveguides,” Phys. Rev. B, vol. 75, 245405 (2007).

[2] E. K. Keshmarzi, R. N. Tait, and P. Berini, “Near infrared amplified spontaneous emission in a dye-doped polymeric waveguide for active plasmonic applications.,” Opt. Express, vol. 22, 12452 (2014).

choloong.hahn@gmail.com









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