Coupled nanowire-based hybrid plasmonic nanocavities on thin substrates

Pi-Ju Cheng; Chih-Kai Chiang; Yi-Cheng Chung; Chung-Hao Tien; Tzy-Rong Lin

doi:10.1186/1556-276X-9-641

Coupled nanowire-based hybrid plasmonic nanocavities on thin substrates

Nanoscale Res Lett. 2014 Nov 28;9(1):641. doi: 10.1186/1556-276X-9-641. eCollection 2014.

Authors

Pi-Ju Cheng¹, Chih-Kai Chiang², Yi-Cheng Chung³, Chung-Hao Tien⁴, Tzy-Rong Lin⁵

Affiliations

¹ Research Center for Applied Sciences, Academia Sinica, 11529 Taipei, Taiwan ; Department of Photonics, National Chiao Tung University, 30010 Hsinchu, Taiwan.
² Institute of Optoelectronic Sciences, National Taiwan Ocean University, 20224 Keelung, Taiwan.
³ Department of Mechanical and Mechatronic Engineering, National Taiwan Ocean University, 20224 Keelung, Taiwan.
⁴ Department of Photonics, National Chiao Tung University, 30010 Hsinchu, Taiwan.
⁵ Institute of Optoelectronic Sciences, National Taiwan Ocean University, 20224 Keelung, Taiwan ; Department of Mechanical and Mechatronic Engineering, National Taiwan Ocean University, 20224 Keelung, Taiwan.

Abstract

We theoretically analyze nanowire-based hybrid plasmonic nanocavities on thin substrates at visible wavelengths. In the presence of thin suspended substrates, the hybrid plasmonic modes, formed by the coupling between a metal nanowire and a dielectric nanowire with optical gain, exhibit negligible substrate-mediated characteristics and overlap better with the gain region. Consequently, the confinement factor of the guided hybrid modes is enhanced by more than 42%. However, the presence of significant mirror loss remains the main challenge to lasing. By adding silver coatings with a sufficient thickness range on the two end facets, we show that the reflectivity is substantially enhanced to above 50%. For a coating thickness of 50 nm and cavity length of about 4 μm, the quality factor is above 100.

Keywords: Laser reonators; Nanomembrane; Nanowires; Semiconductor lasers; Surface plasmons; Waveguides.