Pure amplitude and wavelength modulation spectroscopy for detection of N2O using a three-sections quantum cascade laser
We report on a novel quantum cascade laser (QCL) capable of operating in pure amplitude or wavelength modulation configuration thereby allowing the acquisition of background-free gas absorption-line profiles using quartz-enhanced photoacoustic spectroscopy (QEPAS). The QCL is composed of three electrically independent sections: Gain, Phase (PS) and Master Oscillator (MO). The non-uniform pumping of these three QCL sections allows laser wavelength tuning with constant optical power and vice-versa. Pure QEPAS amplitude modulation operating conditions were obtained by modulating the PS current, while pure wavelength modulation was obtained by modulating the MO section and slowly scanning the PS current.
quartz tuning fork; photoacoustic spectroscopy; quantum cascade laser; gas sensing