Ringing phenomenon in chaotic microcavity for high-speed ultra-sensitive sensing

Abstract

The ringing phenomenon in whispering-gallery-mode (WGM) microcavities has demonstrated its great potential for highly-sensitive and high-speed sensing. However, traditional symmetric WGM microcavities have suffered from an extremely low coupling efficiency via free-space coupling because the emission of symmetric WGMs is non-directional. Here we report a new approach for high-speed ultra-sensitive sensing using the ringing phenomenon in a chaotic regime. By breaking the rotational symmetry of a WGM microcavity and introducing chaotic behaviors, we show that the ringing phenomenon in chaotic WGM microcavities extends over both the positive and the negative frequency detune, allowing the ringing phenomenon to interact with analytes over a much broader bandwidth with a reduced dead time. Because the coupling of the chaotic microcavity is directional, it produces a significantly higher signal output, which improves its sensitivity without the need of a fiber coupler.

Optical vector analysis with attometer resolution, 90-dB dynamic range and THz bandwidth

“…By applying an OFC, OVA with a record resolution of 334 Hz (attometer level), a dynamic range of 90 dB and a measurement range of 1.025 THz was experimentally demonstrated. The proposed method has the potential to be a prevailing method for characterization of a variety of emerging optical devices and provide support for many frontier researches, such as on parity-time symmetry [1], optical nanoparticle detection [2], electromagnetically induced transparency [3], on-chip optical signal processing [4], ultra-sensitive optical sensing [5] and so on.…”

“…Recently, optical devices to manipulate the magnitude and phase of optical signals with ultra-high resolution, ultra-wide bandwidth and ultra-large dynamic range are of fundamental importance for non-Hermitian photonics based on parity-time (PT) symmetry [1], optical nanoparticle detection [2], electromagnetically induced transparency [3], on-chip optical signal processing [4], ultra-sensitive optical sensing [5] and so on. These emerging optical devices put forward very urgent and stringent requirements of the measurement technology in terms of resolution, bandwidth, and dynamic range.…”

“…For example, an ultra-narrow-band fiber Bragg grating (FBG) with a 3-MHz linewidth [6], an on-chip optical isolator with a bandwidth of 0.61 MHz [4], and a high-Q optical micro-resonator with a Q value of 1.7 × 10 10 (11.4-kHz or 91.2-attometer bandwidth in the 1550-nm band) [7] were proposed to improve the sensitivity of optical sensing system, which, obviously, needs an ultra-high resolution optical measurement method to implement the sensing demodulation. Similarly, ultra-narrow bandwidth phenomenon, such as spectral hole burning with a 172-kHz notch in Pr:YSO [8], PTsymmetry breaking with MHz-bandwidth resonance in whispering-gallery-mode microcavities [1], and ringing phenomenon in chaotic microcavity [5], has the capability of finely spectral manipulation, which also demands a measurement approach with attometer-level resolution. On the other hand, the spectra of a majority of optical devices and phenomena should be measured in a range of hundreds or even thousands of GHz.…”

Coupling analysis of high Q resonators in add-drop configuration through cavity ringdown spectroscopy

“…The dispersion of τʼs values can be related to the same effects we discussed during the stationary analysis, i.e. electric noise of the detectors and power fluctuations of the laser source, but also to the mathematical complexity of the fitting functions (24) and (25). In fact, due to this complexity, it is possible that fminsearch could converge in a region of relative minima close to the absolute minimum associated with the expected values.…”

“…The main motivation for this work has been to implement an original technique based on cavity ringdown spectroscopy (CRDS) which is capable of uniquely assessing the various parameters of a WGM resonator in the add-drop configuration by using a single set of measurements. CRD based techniques may, similar to cavity ringup (CRU) [22], allow us to assess intrinsic fundamental properties of the resonators, thanks to their high speed processing capabilities [23,24].…”