Abstract
Microcavities are used for resonantly enhanced interactions of light with matter or particles. Usually, the resonator’s sensitivity drops down with every particle attached to its interface due to the inherent scattering losses and the corresponding degradation of the optical quality factor. Here, we demonstrate, for the first time, a hybrid resonator made of a dielectric disk and a continuous membrane. The membrane is evanescently coupled to the disk while both membrane and disk are mechanically separated. Therefore, the optical mode is co-hosted by the disk and the membrane, while we use a nanopositioning system to control the disk motion. We experimentally demonstrate that spreading scatterers on the membrane and then moving the membrane parallel to the disk brings different scatterers into and out of the optical-mode region. We also show that the membrane’s motion toward the disk results in a 35 GHz drift in the optical resonance frequency. The membrane is continuous in two dimensions and can move a practically unlimited distance in these directions. Furthermore, the membrane can move from a state where it touches the disk to an unlimited distance from the disk. Our continuum-coupled resonator might impact sustainable sensors where the perpetual motion of analytes into and out of the optical-mode region is needed. Additionally, the membrane can carry quantum dots or point defects such as nitrogen-vacancy centers to overlap with the optical mode in a controllable manner. As for non-parallel motion, the membrane’s flexibility and its ability to drift resonance frequency might help in detecting weak forces.
Highlights
The use of microcavities1 for detection2–5 and studying samples in the nanoscale is a highly active field
In a more scientific language, resonance enhancement scales with the optical quality factor of the resonator, Q, divided by the volume of its electromagnetic resonance, V
Our experimental results show that the resonance frequency increases with the gap (Fig. 2, black circles)
Summary
The use of microcavities for detection and studying samples in the nanoscale is a highly active field. Microcavities support multiple constructive interferences to enhance the interaction of light with an analyte Another enhancement mechanism relates to confining the light in the dimensions perpendicular to its propagation direction. We present a general technique that will permit controlled resonantly enhanced access to quantum dots, nitrogen vacancies, and nanoparticles, among other point-like analytes. Bringing an analyte to close proximity with the optical mode results in a related change in the effective refractive index, leading to scattering or increase in light absorption. These mechanisms are associated with resonance drift, resonance split, or broadening of the resonance linewidth. To measure drifts in resonance frequency, locking mechanisms, such as Pound–Drever–Hall control, were used for detecting analytes scitation.org/journal/app such as nanoparticles. For measuring resonance split, beatnoting laser lines originating from a split resonance were used. for measuring resonance broadening, cavity ring-up techniques were developed and demonstrated to operate at the fastest permitted speed.
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