Nanooptics and photonics
Lasing on the nanoscale: electromagnetic engineering of microcavity lasers and plasmonic nanolasers on threshold
Nosich, A.I.1
1 Laboratory of Micro and Nano Optics, Institute of Radio-Physics and Electronics NASU, vul. Proskury 12, Kharkiv 61085, Ukraine 
E-mail: anosich@yahoo.com

The rapid progress of nanotechnology and its applications in bioscience and health-care requires design and development of efficient miniature sources of coherent light – micro to nanoscale lasers. Here, preliminary modelling becomes crucial for saving significant development time and resources. Particularly important is to use adequate laser models beyond the traditional search for the highest-Q-factor modes of passive resonators. In contrast to common paradigm, we view lasers as open resonators equipped with active regions and containing, in the case of nanolasers, plasmonic lossy elements. Then we study their on-threshold characteristics using full-wave methods of classical electromagnetics. This enables us to adapt the corresponding eigenvalue problems to extracting the threshold values of material gain additionally to the mode emission frequencies. Note that, at threshold, nonlinear effects can be safely neglected. To provide convergence and efficiency, we use singular integral equations, which are regularized and cast to well-conditioned matrix equations. Unlike “brute-force” commercial codes, such advanced electromagnetic modelling enjoys fully controlled accuracy.
This analysis path is novel and exciting. It brings in-depth understanding of micro and nanolasers and enables verification of approximate modelling methods. The presentation is focused on the study of on-threshold characteristics of optical microcavity and nanocavity lasing systems including various plasmonic lasers. Considered configurations are based on metal strips, wires and tubes embedded into quantum wires with gain and studied in the optical range of wavelengths. The lasers built on sub-wavelength metal and dielectric nanoparticle elements and associated high-Q lattice modes of periodic arrays of are also discussed. 

1.	Shapoval O.V., Kobayashi K., Nosich A.I. Electromagnetic engineering of a single-mode nanolaser on a metal plasmonic strip placed into a circular quantum wire // IEEE J. Sel. Top. Quant. Electron. – 2017. – 23. – P. 1501609.
2.	Natarov D.M., Benson T.M., Nosich A.I. Electromagnetic analysis of the lasing thresholds of hybrid plasmon modes of a silver tube nanolaser with active core and active shell // Beilstein J. Nanotech. - 2019. - 10. - P. 294-304.