Virtual Vernier Effect Harmonics for Enhanced Fabry-Perot Interferometer Sensing

The present paper proposes the implementation of Vernier-effect harmonics through the virtualization of different reference cavities. A Fabry-Perot interferometer (FPI), actuated by a piezoelectric transducer (PZT), was employed as the sensing element. Subsequently, the sensitivity of the dynamic range was investigated for both the individual interferometer and the implementation of the Virtual Vernier effect. A sensitivity of (8 ± 0.05)×10^-3 nm/nm was achieved for the single sensor measurement. Considering the implementation of the Vernier effect, the following sensitivities were obtained: (65.6 ± 0.08)×10^-3 nm/nm for the fundamental, (132 ± 1)×10^-3 nm/nm for the first harmonic, and (192 ± 1)×10^-3 nm/nm for the second harmonic. Furthermore, a maximum dynamic range of 11.25 μm and a maximum resolution of 5 pm were achieved. This study highlights the advantages of simultaneously measuring both a single sensor cavity and a harmonic of the Virtual Vernier effect, in order to achieve large dynamic ranges along with high resolution.