Detection of CO in air using diode laser pumped difference-frequency generation in a modular setup

Based on our recent work in the field of difference-frequency generation (DFG) using two diode lasers as pump sources and AgGaS2 as a non-linear crystal, a modular setup with new features was developed. With one pair of diode lasers, it was possible to cover a spectral region of 21 cm(-1) around 2100 cm(-1). The achieved optical output power was > 100 nW at a signal-to-noise ratio of 1000:1. Using a high-resolution spectroscopy module in our setup, several high-resolution spectroscopic experiments were carried out. Besides 22 CO lines of different isotopomers, OCS, and N2O lines could be measured within one scan. To determine the spectroscopic features of our generated IR-radiation, self-, noble gas, air, hydrogen CO2, and oxygen broadening experiments on the R(3) line of the (CO)-C-13-O-16 were performed. Applying a trace gas detection module, CO under different conditions was detected. The capabilities of the module for trace gas detection under background and urban conditions as well as for process monitoring or medical investigations are demonstrated. (C) 1999 Elsevier Science Ltd. All rights reserved.