Tunable diode laser spectroscopy with electronically controlled background RAM nulling

An electronically-controlled fibre-optic RAM nulling method is presented for tunable diode laser spectroscopy (TDLS) of gases. An electronic variable optical attenuator and a 1x2 optical switch are used to demonstrate the cancellation of the background RAM signal that limits the detection sensitivity in 1f WMS. This is an significant improvement upon the generic RAM nulling method that has recently been shown to be well suited to direct recovery of the absolute gas absorption line shapes of gases that commonly encountered in process control applications. © 2012 SPIE.