InGaAsP/InP subwavelength waveguide plasmonic lasers
Han Yeh1*, Chien Ju Lee1, Yen Chun Chen1, Shan Gir Gwo2, Jer Shing Huang3, Wen Hao Chang1
1Department of Electrophysics, National Chiao Tung University, Hsinchu, Taiwan
2Department of Physics, National Tsing Hua University, Hsinchu, Taiwan
3Department of Chemistry, National Tsing Hua University, Hsinchu, Taiwan
* presenting author:Han Yeh,
We demonstrate plasmonic lasing from InP subwavelength waveguides with embedded InGaAsP multiple quantum wells on Al2O3-capped single crystalline gold flakes, i.e., a semiconductor-insulator-metal (SIM) plasmonic structure. The dimension of the InP waveguides were reduced to subwavelength scales, such that no optical mode can be supported in the waveguides. Numerical simulations suggest that the SIM structure can confine electromagnetic energy not only in the nanometer scale insulating layer, but also in the waveguide layer. Such hybrid plasmonic waveguide modes can be classified into the fundamental mode and high-order modes, according to the electric field antinodes in the thin insulating layer. Unlike previously reported nanowire plasmonic lasers, we found that plasmonic lasing from the InP subwavelength waveguides occurs only at higher-order plasmonic modes, of which the electric field confined in the waveguide is mostly parallel to the quantum well plane. The electric field distribution of the higher-order modes exhibits a better overlap and polarization match with the gain medium, and thereby providing a better feedback mechanism for plasmonic lasing oscillations. Temperature dependent measurements reveal that the lasing threshold increases with the increasing temperature, implying that the plasmonic lasing is hindered predominantly by the ohmic loss of plasmonic fields in metal.

Keywords: plasmonic laser, subwavelength waveguides