Intracavity laser spectroscopy: an old field with new prospects for combustion diagnostics

Intractivity laser spectroscopy is an analytical technique which offers the possibility of making sensitive measurements of atomic and molecular species in combustion environments. Absorption signals can be as much as a million times greater than those obtained from conventional absorption spectroscopy. In this paper we examine the main experimental and theoretical approaches that have been taken to understand how the technique works. We show that the two principal theories of intracavity spectroscopy can be reconciled and that recent theoretical and experimental advances allow intracavity spectroscopy to give reliable and reproducible results which can be used for quantitative measurements. Possible applications of the the technique as a diagnostic technique for combustion applications are proposed.