Abstract

Coherent anti-Stokes Raman spectroscopy (CARS) is a form of nonlinear-optical sepctroscopy that is particularly useful for spectroscopic sensing of high-temperature or hostile media. Our research in this are [1-3] has evaluated optical parametric oscillator (OPO) devices as an alternative to dye lasers in providing the tunable coherent light needed for this purpose. We now report a further development of the OPO CARS theme, following earlier demonstrations [4,5] that injection seeding by a single-mode external-cavity diode laser (ECDL) can control the optical bandwidth and outut wavelengths of a pulsed OPO with a passive ring cavity. We exploit the possiblity of injection-seeding a free-running OPO at two (or more) independent optical frequencies falling within its intriniscally broad optical bandwidth, [3,5] with a pair of ECDLs used to seed a single OPO. This enables single-shot, two- colour multiplex OPO CARS measurements[6] that are useful for combustion diagonostics, as has previously been demonstrated with dye-laser sources.[7]

© 1996 Optical Society of America