Low-concentration liquid sensing by an acoustic Mach-Zehnder interferometer in a two-dimensional phononic crystal

Salman A., KAYA O. A., Cicek A., ULUĞ B.

JOURNAL OF PHYSICS D-APPLIED PHYSICS, vol.48, no.25, 2015 (SCI-Expanded) identifier identifier

  • Publication Type: Article / Article
  • Volume: 48 Issue: 25
  • Publication Date: 2015
  • Doi Number: 10.1088/0022-3727/48/25/255301
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Keywords: Mach-Zehnder interferometer, liquid concentration sensing, phase shift, finite-element method, GASOLINE, SENSOR, WAVES
  • Akdeniz University Affiliated: Yes


Mach-Zehnder interferometer formed by liquid-filled linear defect waveguides in a two-dimensional phononic crystal is numerically realized for sensing low concentrations of an analyte. The waveguides in the square phononic crystal of void cylinders in steel, as well as their T branches and sharp bends are utilized to construct interferometer arms. Sensing low concentrations of ethanol on the order of 0.1% in a binary mixture with water is achieved by replacing the contents of a number of waveguide core cells on one arm of the interferometer with the analyte. Computations are carried out through the finite-element method in an approach that takes the solid-liquid interaction at the waveguide core cells into account. Band analyses reveal linear variation of the central frequency of the transmission band within a band gap for ethanol concentrations up to 3.0%. Phase difference due to the imbalance of the sample and reference arms of the interferometer also varies linearly with ethanol concentration, leading in turn to a cosine variation of the Fourier component of the temporal interferometer response at the central input-pulse frequency. The induced phase difference in the investigated configuration becomes a -0.78 pi and -0.65 pi per percent increase of ethanol concentration as calculated from the band-structure and transient data, respectively. This is confirmed by transient finite-element simulations where totally destructive interference occurs for a concentration of approximately 1.5%. The proposed scheme, which can easily be adopted to other binary mixtures, offers a compact implementation requiring small amounts of analyte.