A Gradient-Asymmetrically Localized Three-Beam Array for Mass Sensing With Warning

Abstract

A mass sensing scheme with a two-warning function is proposed with a gradient-asymmetrically localized three-beam array (GALA), coupled with a variable length overhang, which is defined as an overhang of varying length along the transversal axis of the array. Compared with that of a symmetrically localized three-beam array (SLA), the amplitude change in the GALA prototype is observed to be significantly increased by about 100% with the localized first mode. While two intersections, appeared in three amplitude curves with respect to mass perturbation, are believed to be capable of playing early mass warning functions. These indicate that gradient-asymmetrical coupling, changing the mechanism of energy transfer, shows different energy localization characteristics from a symmetrical one. A localization factor of characterizing the inhomogeneity in energy localization is found to monotonically decrease from 3.10 to 1.70 with the gap between support and overhang while monotonically increasing from 2.75 to 3.10 with the width of overhang, and thus overlapped at 2.90. This implies that a very similar localized state with the same localization factor might be achieved by adjusting different overhang geometry. An optimal gradient angle of 7° with the highest amplitude change, corresponding to the maximum energy localization rate under a coupling ratio of 2.76, is further theoretically observed in GALA. The proposed scheme is believed to be applicable to detecting and warning of gas leak, dust pollution, harmful chemicals, and other applications.