A convenient acoustic measurement of femtosecond filamentation based on a cell phone

The acoustic diagnostic method has been widely used in diagnosing femtosecond filamentation. In this work, acoustic measurements of femtosecond laser filamentation and weakly air-ionized region are conducted using a readily available portable device - a cell phone. The signal is extracted by employing digital signal processing method of Fourier transformation filtering. The results demonstrate that the method can be used for effective measurements even in noisy environments. This greatly enhances the accuracy and portability of the acoustic method, providing a practical approach for improving acoustic diagnostics.