Detection of Ultrasonic Waves Using Resonant Cylindrical Cavity for Defense Application

A novel resonant standoff quantum cascade laser (QCL) spectroscopy-based technique has been demonstrated for the detection of hazardous molecules (chemicals and explosives) on adsorbed surfaces, such as plastics and cloths, vapors, and in aerosols form in open air. Laser photoacoustic spectra of various trace molecules in the midinfrared spectral band 7– $9~\mu \text{m}$ have been recorded. Cylindrical tube coupled with microphone detector has been developed for the detection in trace amounts. The cylindrical tube has been developed for a compatible microphone detector working at resonant frequency of 40 kHz. The devised QCL-based acoustic detection setup has high selectivity and sensitivity. The present technique has been developed for screening of suspicious objects for security applications. It has the potential to be converted into a handy product.