WGM microresonators: sensing, lasing and fundamental optics with microspheres

Abstract

Glass microsphere resonators that support optical resonances known as whispering-gallery modes are unique tools for studying and exploiting optical effects under extremely well controlled conditions. In this paper, a review focusing mostly on glass microsphere resonators is presented. First, a brief historical background is given in which is shown how the stateof-the-art has grown from novel optical resonators to the ultrahigh Q cavities used in cutting-edge experiments. After the basic properties of microsphere resonators are outlined some of the recent experiments involving microsphere resonators are discussed, although some discussion involving polymeric microspheres is also included. The use of doped and undoped microspheres in optical signal processing, optical sensing and quantum optics is highlighted. Finally, there is a brief review of recent optomechanical experiments that use microspheres.

Whispering-gallery mode lasers for biosensing: a rationale for reducing the lasing threshold

“…The transition between the fluorescence and the stimulated emission regimes can be clearly seen around 7 μW. Similarly the measured Q factor, defined as λ/Δλ also increases beyond the lasing threshold, from 4×10 3 to almost 8×10 3 . As the Q factor describes the stored energy in the resonator, a higher gain in the resonator, especially upon lasing will increase the stored energy and therefore the Q factor.…”

“…diameter, sphericity) and optical properties, but also by the surrounding refractive index. Two distinct approaches have been developed to exploit WGMs, in a wide range of resonator geometries ranging from rings/toroids [2] and spheres [3] to cylinders and capillaries [4] . The first approach is based on using evanescent field coupling between a phasematched tapered optical fiber (or prism) and the resonator, and scanning across a narrow wavelength range with a distributed feedback laser to identify the resonance positions and linewidths [5] .…”

Droplet lasers: a review of current progress

“…The broad field of whispering gallery mode sensors using solid cavities [15], [28] is mature and has a wide range of demonstrated sensing capabilities, as well as more fundamental applications in the study of optomechanics. This far and away outstrips the utility to date of droplet lasers, which are an unusual subset of active media within the typically passive cavity sensor field.…”

Hybrid Lasers Based on CdSe/CdS Core/Shell Colloidal Quantum Rods on Silica Microspheres

“…Whispering-gallery-mode (WGM) microsphere resonators can have extremely high Q factors (>10 8 ) and are therefore attractive for development of a variety of photonics devices such as miniature lasers, single-photon emitters, sensors and, as templates, for fundamental studies of light-matter interaction [2,3]. Here we report on tunable laser emission from silica microspheres coated with CdSe/CdS core/shell nanorods whose lasing thresholds and modality are controllable by the pump coupling conditions.…”