ABSTRACT
High-sensitivity monitoring of combustion species using compact semicon ductor lasers began shortly after their invention, with portable sensors for monitoring CO emissions from automobile exhausts and in-situ measure ments in laboratory burners appearing by the mid-1970s [1,2]. Today, packages of multiple near-IR diode laser sensors are included by NASA as part of the atmospheric and environmental instrumentation suite of robotic Martian explorers. Significant attributes of tunable diode laser (TDL) sensors based on absorption spectroscopy include: simplicity of design and operation, leading to fully autonomous sensors; high-speed wavelength tuning, leading to high-bandwidth sensor response; and lowcost, rugged, and often fiber-coupled configurations, leading in turn to important applications in practical, industrial-scale combustor facilities. The combination of these attributes is enabling integration of diode laser sensors within closed-loop combustion control systems, allowing direct monitoring of im portant combustion parameters such as temperature and individual species concentration levels [3,4] (see also Chapter 21 and 26).
