IR-fibre optical components for trace gas analysis equipment

Investigations concentrated on infrared optical properties of zirkonium fluoride monomode fibres. As a main outcome, monomode fibres are characterized by nearly Gaussian far fields, which are essentially independent of the launching conditions. They act as spatial filters with suppression of higher laser modes, detrimental in trace gas analysis. Transmission levels for the "useful" modes are up to 60 per cent for fibre samples of some 10 cm. Under the same condition, optical backward reflection levels as low as 10 (exp -6) were realized. Direct coupling of a fibre to t diode laser as a prerequisite for pigtailing can result in some 10 per cent of the total power launched to the fibre. As an issue, monomode infrared fibres potentially could represent highly performing components for trace gas analyzer equipment based on infrared diode lasers.