Detection of dimethyl methylphosphonate (DMMP) with an interband cascade laser sensor

We demonstrate the sensitive detection of dimethyl methylphosphonate (DMMP, a hydrogen-bond (HB) basic phosphonate ester) using additional optical loss induced in an interband cascade laser with top optical cladding layer replaced by an exposed sensing window coated by a HB acidic sorbent layer. Thin coatings of the sorbents HCSFA2 and oapBPAF were deposited on the sensing window to allow reversible capture and concentration of DMMP for optical interrogation. Analyte levels down to 0.1 mg/m³ (∼20 ppb) were tested and successfully detected by monitoring the laser's threshold or its output power at a fixed bias as a function of DMMP delivery concentration.