Carbon monoxide gas sensor based on an <i>α</i> -Fe ₂ O ₃ /reduced graphene oxide quantum dots composite film integrated Michelson interferometer

Abstract A carbon monoxide (CO) sensor based on a Michelson interferometer combined with α -Fe 2 O 3 /reduced graphene oxide quantum dots (rGOQDs) composite film is proposed and fabricated. First, a waist-enlarged taper is formed between the single-mode fiber (SMF) and the no-core fiber (NCF), then the other end of the NCF is spliced with a section of thin-core fiber (TCF). The end of the TCF is coated with a layer of silver film to enhance the reflection. Thus, a Michelson interferometer comprising SMF–NCF–TCF is formed. The α -Fe 2 O 3 /rGOQDs composite film is deposited on the outside surface of the TCF. The specific adsorption of CO by the composite film leads to a change in the sensor’s effective refractive index, realizing the detection of CO. The results show that the interference intensity of the monitoring valley decreases with increase in the concentration of CO. The sensitivity of the sensor is 0.057 dBm ppm −1 , the detection limit of the sensor is 105 ppb and the response time and recovery time are 70 s and 100 s, respectively. The sensor has the advantages of high sensitivity, high selectivity and simple structure, and it is expected to be used for the detection of low concentrations of CO gas.