Modelling of open photoacoustic resonators

Shape Optimization of an Open Photoacoustic Resonator

“…The microphone has a resonance at around 25 kHz and has a fairly flat response between 35 kHz and 65 kHz. The frequency response plot of the microphone can be found in our previous work [21]. The microphone output represents a digital pulse density modulated (PDM) signal which is send through a low-pass filter circuit for demodulation.…”

“…Furthermore, to verify the optimization results, the PA signal of the optimized resonator is simulated using VT-PML, VT-BEM and AME-VT approaches between 10 kHz and 60 kHz. The implementation of these simulation approaches is here briefly described and a detailed description of the method can be found in our previous work where we simulated the PA signal in the reference resonator [21]. The meshing and implementation of the PA simulations in this work are performed in a similar manner as described for the reference resonator.…”

“…This resonance is selected for optimization because PA glucose measurements using the open T-shaped resonator are usually performed at this frequency [13,14]. The resonance spans a relatively wide frequency range between 48 kHz to 51 kHz due to a superposition of two resonances [21]. Therefore, the PA signal is calculated in this range during the optimization.…”

“…We have previously described three different approaches for simulating the PA signal in open resonators: the viscothermal model with perfectly matched layers (VT-PML), the viscothermal model with boundary element method (VT-BEM) and the amplitude expansion model with perfectly matched layers (AME-PML) [21]. The VT-PML was demonstrated to be the most accurate of the three approaches and therefore used to calculate the PA signal in this work.…”

Laser induced thermoelastic contributions from windows to signal background in a photoacoustic cell

“…The detection limit achieved was at ppm levels with merely a few tens of microwatts incoherent source [ 14 , 15 ]. In other reports, optical windows were even discarded and replaced with buffers [ 16 , 17 ], which facilitates the so-called “open path detection” modality [ 18 ]. Such designs completely avoid window absorption, but the loss of optoacoustic energy confinement due to the open design significantly degrades the SNR.…”