High sensitivity and fast detection system for sensing of explosives and hazardous materials

Abstract

We demonstrate a high sensitivity and fast detection system for sensing of explosives and hazardous materials based on the external cavity quantum cascade laser (ECQCL). In this system, one galvanometer is utilized as the tuning component of the ECQCL to get high wavelength scanning speed. Meanwhile, the driving module of the galvanometer and the analog to digital conversion (ADC) module for data acquisition are synchronized, which brings in great significance for fast high sensitivity detection. For one thing, this synchronization exactly defines the data of each scanning period during data acquirement and processing, which enables our system to avoid data dislocation and cumulative error. For another, enough averaging times are allowed to obtain high sensitivity while detection speed is high enough for practical application. To verify the practical application effect, this system was utilized to detect trace amount of adsorbed trinitrotoluene (TNT) on the People's Republic of China Resident Identity (ID) Card. Although the wavelength tuning rate was as high as 17400 cm−1/s over the range of 1280–1454 cm−1(∼6.88–7.81 µm) with scanning frequency of 100 Hz, a TNT detection sensitivity of 1 μg/cm2 was achieved with detection speed of one result per second through multiple averaging technique.