Laboratoire Matière et Systèmes Complexes

In phononic crystals, the propagation of acoustic waves does not follow the same rules as in standard homogeneous media [1,2]. In particular, absolute band gaps can exist, making phononic crystals promissing candidates for applications such as acoustic filters, silent blocks or waves guides [3]. They can also exhibit resonant tunneling [4] or sub-wavelength imaging [5].

Bubble phononic crystal

Two layers of air inclusions in an elastic matrix. Diameters are 78µm, lattice constant 200µm.

Among all the components one can think of to create a phononic crystal, the case of air bubbles in a liquid has been shown to be a very promissing choice. Theories predict indeed that crystals with air inclusions in a liquid exhibit the widest band gaps ever reported [6,7]. But the practical implementation is difficult: generating equally sized bubbles arranged on a crystal lattice is not an easy task.

We have designed phononic crystals of bubbles using soft lithography techniques. Transmission measurements confirm the existence of wide and deep minima of transmission [8]. Interestingly, the first minimum is due to the combined effect of Bragg reflections (Bragg gap, BG) and bubble resonances (hybridization gap, HG).

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 [3] A. Khelif, A. Choujaa, S. Benchabane, B. Djafari-Rouhani, and V. Laude, Applied Physics Letters 84, 4400 (2004).
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 [5] A. Sukhovich, B. Merheb, K. Muralidharan, J. O. Vasseur, Y. Pennec, P. A. Deymier, and J. H. Page, Physical Review Letters 102, 154301 (2009).
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 [8] V. Leroy, A. Bretagne, M. Fink, H. Willaime, P. Tabeling, A. Tourin, Applied Physic Letters 95 171904 (2009). (pdf)

COLLABORATIONS:
 Institut Langevin, Paris, France (A. Bretagne, M. Fink, A. Tourin)
 Laboratoire MMN, Paris, France (P. Tabeling, H. Willaime)