Design and development of a tunable External Cavity Diode Laser (ECDL) emitting in violet-blue spectral region for measuring NO2 trace gas

An instrument based on a tunable External Cavity Diode Laser (ECDL) with stable and narrow line-width emission in violet-blue spectral region (430 nm 470 nm) will be designed and developed. The performance of the instrument will be tested in high-resolution spectroscopy applied to environment. The instrument will be used to measure in real time Nitrogen dioxide (NO2) trace gas. The selected spectral range coincides with a strong optical absorption cross section of NO2 in the spectral range (400 nm 500 nm) with an average of about 0.6X10^-18 cm^2. In addition, in this spectral region, the detection is not affected by interferences from other gases commonly existing in the air, which improves the selectivity of the instrument. By scanning an individual absorption line of NO2 using a single narrow laser linewidth at room temperature and at atmospheric pressure, and precisely measuring the magnitude of absorption, NO2 concentration will be obtained with high sensitivity. The estimation of the performance of the instrument developed will be based mainly on the low detection limit achieved, the accuracy and repeatability of the measurements, the versatility and ease of use of the instrument. On the other hand, the measurements obtained by the instrument developed will be validated using a standard technique (chemiluminescence analyzer) and different certified known concentrations of NO2 gas cylinders.