Plasmon-assisted low-threshold nanolasers

Low power consumption is of great importance for on-chip optical applications of nanolasers. To reduce the lasing threshold, a high quality factor and strong Purcell effect are vital, while the latter is often hindered by the above-diffraction-limit mode volume of photonic cavity, and its improvement generally requires complicated cavity design. We show that by coupling to an off-resonant plasmonic antenna, the lasing threshold of a photonic cavity can be reduced over a wide range of parameters where the plasmon-assisted coherent light-matter interaction dominates over the plasmon-induced dissipation. We develop a semiclassical model of a two-level nanolaser for such a hybrid plasmonic-photonic cavity, which is consistent with the quantum description of the spectral density of a hybrid cavity. The analytical expression of the lasing threshold is derived, which can be utilized to optimize the system parameters associated with cavities designed to obtain the minimum lasing threshold. Through comprehensive study, we find that compared to all-dielectric photonic cavity, a hybrid cavity can have prominent advantages in lasing with lower threshold, narrower emission linewidth, and sustaining the higher-power output of laser field. Our paper demonstrates the possibility of utilizing a hybrid plasmonic-photonic cavity to fabricate room-temperature low-threshold nanolasers.