Abstract
When light is brought to a standstill, its interaction with gain media increases dramatically due to a singularity in the density of optical states. Concurrently, stopped light engenders an inherent and cavity-free feedback mechanism, similar in effect to the feedback that has been demonstrated and exploited in large-scale disordered media and random lasers. Here we study the spatial, temporal and spectral signatures of lasing in planar gain-enhanced nanoplasmonic structures at near-infrared frequencies and show that the stopped-light feedback mechanism allows for nanolasing without a cavity. We reveal that in the absence of cavity-induced feedback, the subwavelength lasing mode forms dynamically as a phase-locked superposition of quasi dispersion-free waveguide modes. This mechanism proves remarkably robust against interface roughness and offers a new route towards nanolasing, the experimental realization of ultra-thin surface emitting lasers, and cavity-free active quantum plasmonics.
Highlights
When light is brought to a standstill, its interaction with gain media increases dramatically due to a singularity in the density of optical states
At the stopped light (SL) point, the overall energy flow effectively cancels, forming a characteristic closed-loop vortex[28] (Fig. 1a), which results in a strong enhancement of the local density of optical states (LDOS) that is only limited by dissipative loss
We initially focus on this photonic design, but will demonstrate later that it is possible to realize plasmonic designs, where multiple SL points fall onto a bound plasmonic mode
Summary
When light is brought to a standstill, its interaction with gain media increases dramatically due to a singularity in the density of optical states. We reveal that in the absence of cavity-induced feedback, the subwavelength lasing mode forms dynamically as a phaselocked superposition of quasi dispersion-free waveguide modes This mechanism proves remarkably robust against interface roughness and offers a new route towards nanolasing, the experimental realization of ultra-thin surface emitting lasers, and cavity-free active quantum plasmonics. At the SL point, the overall energy flow effectively cancels, forming a characteristic closed-loop vortex[28] (Fig. 1a), which results in a strong enhancement of the local density of optical states (LDOS) that is only limited by dissipative loss Combined with gain, this SL feedback mechanism can lead to coherent amplification of the trapped photons via stimulated emission processes. We identify the mode-locking mechanism that leads to the selflocalization of light on subwavelength scales and verify its applicability to both the SL nanolaser and an alternative SL spasing design
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