Collective lasing from a linear array of dielectric microspheres with gain

Anjani Kumar Tiwari,Balu Chandra,Ravitej Uppu,Sushil Mujumdar

doi:10.1364/oe.20.006598

Abstract

We experimentally study the optical emission behavior of a linear array of dielectric microspheres with gain. The microspheres are randomly arranged and well-separated, and can only couple via radiative modes. We observe resolution-limited, ultra-narrowband modes in the longitudinal emission, which constitutes collective lasing from the entire array, inferred from the observation of a lasing threshold. The lasing modes show wavelength selectivity, wherein the lasing probability is large only in specific frequency bands while being inhibited at other wavelengths, a behavior which is independent of the degree of configurational randomness. Analysis of the frequency bands indicates the participation of Fabry-Perot resonances of the individual microspheres in the collective emission.

Highlights

We present experimental reports on the collective behavior of a linear array of amplifying spherical microcavities
The microspheres are separated by several tens of wavelengths, thereby admitting only radiative modes in the transport. We study both quasiperiodic and random configurations of such linear arrays
While the individual microspheres yield the expected Mie whispering gallery modes (WGM) lasing, collectively they manifest another lasing mechanism which gives ultra-narrowband modes

Summary

Introduction

“Highly efficient optical coupling and transport phenomena in chains of dielectric microspheres,” Opt. Lett. N. Astratov, “Observation of nanojet-induced modes with small propagation losses in chains of coupled spherical cavities,” Opt. Lett. To our knowledge, there have been no attempts to study linear chains of physically well-separated, amplifying microcavities, and to identify any resultant collective phenomena. We study both quasiperiodic and random configurations of such linear arrays.

Results

Conclusion