Abstract: A method of monitoring gas in a downhole environment is discussed which provides downhole a mid-infrared light emitting diode, operates the diode to transmit respective infrared signals on a first optical path extending from the diode through a downhole gas sample and a second optical path extending from the diode through a reference gas sample, detects the transmitted infrared signals, and determines the concentration of a component of the downhole gas sample from the detected signals.

Abstract: A method of monitoring gas in a downhole environment is discussed which provides downhole a mid-infrared light emitting diode, operates the diode to transmit respective infrared signals on a first optical path extending from the diode through a downhole gas sample and a second optical path extending from the diode through a reference gas sample, detects the transmitted infrared signals, and determines the concentration of a component of the downhole gas sample from the detected signals.

Abstract: A radiation source (30) is provided comprising a first active layer (42) coupled to a second active layer (62), wherein the first active layer (42) produces primary radiation of frequency v1 by appropriate stimulation, and the primary radiation is converted by the second active layer (62) to secondary radiation of frequency v2 for subsequent output. The coupling between the first and second active layers is achieved by an intermediary layer (58) disposed between the first active layer (42) and the second active layer (62). The radiation source (30) further comprises a p-n junction (48) incorporated in the first active layer (42), where injection of electrical carriers into the first active layer (42) from the p-n junction stimulates the first active layer (42) to emit the primary radiation.