技術論文とプレゼンテーション

Open photoacoustic cells enable rapid gas exchange and continuous-flow operation but often suffer from reduced acoustic selectivity and increased susceptibility to external acoustic disturbances. In this work, we present a modified open photoacoustic resonator in which longitudinal slits are introduced along the mantle of a cylindrical cavity. Rather than serving solely as gas inlets, the slits are positioned along the nodal lines of a selected acoustic eigenmode, enabling passive geometry-driven mode selectivity. The acoustic behavior of the proposed design was investigated using the Pressure Acoustics interface in COMSOL Multiphysics®. An eigenfrequency analysis was first performed to identify the resonant modes and determine the nodal-line locations. Frequency-domain simulations were then used to evaluate the acoustic pressure response of resonators with and without slit patterning. The model was developed specifically for this study and was not based on an Application Library example. The numerical predictions were experimentally validated via photoacoustic measurements with water vapor as the absorbing gas. The simulations show that the slit arrangement preserves the target resonance while increasing acoustic radiation losses for competing modes with incompatible pressure distributions, thereby suppressing unwanted resonances. The measured photoacoustic spectra exhibit the same qualitative behavior, demonstrating good agreement with the numerical model and confirming the mode-selective effect of the nodal-line slit pattern. The presented approach provides a simple passive method for tailoring the modal characteristics of open photoacoustic resonators without sacrificing the advantages of open-cell operation. This design strategy can improve modal purity, reduce sensitivity to external acoustic noise, and support the development of fast-response photoacoustic gas sensors with enhanced measurement reliability.