Single-atom detection using whispering gallery modes of microdisk resonators

Optical whispering gallery mode (WGM) microresonators, confining resonant photons in a microscale resonator for long periods of time, could strongly enhance light-matter interaction, making it an ideal platform for all kinds of sensors. In this paper, an overview of optical sensors based on WGM microresonators is comprehensively summarized. First, the fundamental sensing mechanisms as well as several recently developed enhanced sensing techniques are introduced. Then, differe...

Whispering gallery mode (WGM) resonators are garnering significant attention due to their unique characteristics and remarkable properties. When integrated with optical sensing and processing technology, WGM resonators offer numerous advantages, including compact size, high sensitivity, rapid response, and tunability. This paper comprehensively investigates the optical properties and behavior of WGMs in complex microsphere resonator configurations. The findings underscore the...

We detect 39 nm x 10 nm gold nanorods using a microtoroid stabilized via the Pound-Drever-Hall method. Real-time detection is achieved with signal-to-noise ratios up to 12.2. These nanoparticles are a factor of three smaller in volume than any other nanoparticle detected using WGM sensing to date. We show through repeated experiments that the measurements are reliable, and verify the presence of single nanorods on the microtoroid surface using electron microscopy. At our curr...

We have demonstrated higher-order optical resonance node detection by using an integrated disk microresonator from through port of the coupling bus waveguide. In addition to the fundamental mode, the disk resonator has higher-order whispering gallery modes. The excited second-order higher-order mode has a node at the position where the electromagnetic energy of the fundamental mode is close to a maximum. This high resolution measurement of optical resonance mode profile has a...

The ability to detect and size individual nanoparticles with high resolution is crucial to understanding behaviours of single particles and effectively using their strong size-dependent properties to develop innovative products. We report real-time, in-situ detection and sizing of single nanoparticles, down to 30 nm in radius, using mode-splitting in a monolithic ultra-high-Q whispering-gallery-mode (WGM) microtoroid resonator. Particle binding splits a WGM into two spectrall...

We report on the radiative interaction of two single quantum dots (QDs) each in a separate InP/GaInP-based microdisk cavity via resonant whispering gallery modes. The investigations are based on ab initio coupled disk modes. We apply optical spectroscopy involving a $4f$-setup, as well as mode-selective real space imaging and photoluminescence mapping to discern single QDs coupled to a resonant microdisk mode. Excitation of one disk of the double cavity structure and detectin...

We investigate the interaction between single quantum emitters and non-transversally polarised photons for which the electric field vector amplitude has a significant component in the direction of propagation. Even though this situation seems to be at odds with the description of light as a transverse wave, it regularly occurs when interfacing or manipulating emitters with non-paraxial, guided, or evanescent light. Here, we couple single rubidium atoms to single photons which...

Ultrasensitive optical detection of nanometer-scaled particles is highly desirable for applications in early-stage diagnosis of human diseases, environmental monitoring, and homeland security, but remains extremely difficult due to ultralow polarizabilities of small-sized, low-index particles. Optical whispering-gallery-mode microcavities, which can enhance significantly the light-matter interaction, have emerged as promising platforms for label-free detection of nanoscale ob...

The interaction of whispering gallery modes (WGM) of optical microresonators with subwavelength imperfections has been studied both experimentally and theoretically. This interaction is responsible for the formation of spectral doublets in place of single resonance peaks, and for degrading of Q-factors of the resonances. Within the currently accepted framework the spectral doublets are explained as a result of degeneracy removal of clockwise and counterclockwise WGMs due to t...

We demonstrate the excitation and detection of whispering gallery modes in optical microresonators using a "point-and-play", fiber-based, optical nano-antenna. The coupling mechanism is based on cavity-enhanced Rayleigh scattering. Collected spectra exhibit Lorentzian dips, Fano shapes, or Lorentzian peaks, with a coupling efficiency around 13\%. The spectra are characterized by the coupling gap, polarization, and fiber tip position. The coupling method is simple, low-cost an...