Propagation of pulsed ultrasonic fields in a band gap of a two dimensional phononic crystal

Abstract

A band gap in the transmission spectrum of a finite two dimensional phononic crystal is examined in the time domain using pulsed ultrasonic fields. The phononic crystal consists of a hexagonal array of copper cylinders (r = 1.19 mm) in an aqueous matrix with a lattice constant of 2.9 mm. Measurements of the transmission properties of the sample are performed using ultrasonic wave groups of various center frequencies and bandwidths. Among the band gaps in the low-MHz range, we concentrate on the gap from 1.48 MHz—1.70 MHz. The phase velocity, group velocity, and attenuation coefficient spectra are determined and compared with expectations.