Enhanced-sensitive acoustic sensor based on cascaded dual microfiber knot resonators with Vernier effect

Purpose This paper aims to propose an acoustic sensor for cascaded dual microfiber knot resonators (DMKRs) based on the Vernier effect to amplify the free spectral range (FSR) of the DMKRs, thus improving the sensitivity of acoustic signal detection. Design/methodology/approach To achieve this, two separate microfiber knot resonators (MKRs) are fabricated with the condition that their FSRs are similar but not equal. As a result, the cascaded transmission spectrum generates periodic envelope signals. Findings The sensitivity of the DMKRs acoustic sensor to sound pressure is obtained, resulting in measurements of 8.2 and 1.37 nm/Pa for acoustic signal frequencies of 500 and 1 kHz, respectively. In comparison to the sensitivity of a single MKR acoustic sensor, the sound pressure sensitivity of the DMKRs is amplified. Originality/value The results of this paper show that the cascaded double ring structure has good application prospects for whispering-gallery mode resonators in the field of acoustic sensing, and can improve the acoustic sensing sensitivity. It not only improves the acoustic sensing sensitivity but also suggests potential for the development of more cascade parallel structures and array integration.