Photonic Barcodes Based on a SNAP Microcavity for Displacement Sensing

Barcodes, as a representation of data describing information of the object, have been demonstrated to have a great value for tracking and identifying large amounts of information in our daily lives. Here, we demonstrate a surface nanoscale axial photonics (SNAP) microcavity multimode displacement sensing technology based on photonic barcodes. Based on the characteristic parameters of each order axial mode in the resonance spectrum of SNAP microcavity, the resonance spectrum is converted into a barcode. The correlation coefficient between the barcode to be detected and the standard barcode is calculated by using the method of cross-correlation function to achieve rapid and accurate identification of microcavity displacement. Simulations demonstrate the feasibility of displacement sensing based on photonic barcodes. When the signal-to-noise ratio (SNR) of the noise-containing spectrum is 10 dB, the identification error of the displacement is ±
$0.2 ~\mu \text{m}$
using the discrete wavelet transform (DWT) hard threshold denoising method. This work not only can directly read the displacement from the spectrum, but also has a strong resistance to environmental interference, which lays the foundation for the development of a high-precision, large-range micro-displacement sensor.