Spectroscopic diagnostics of chemical processes: applications of tunable optical parametric oscillators |
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| Authors: | G.W. Baxter M.A. Payne B.D.W. Austin C.A. Halloway J.G. Haub Y. He A.P. Milce J.F. Nibler B.J. Orr |
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| Affiliation: | (1) Department of Chemistry and Centre for Lasers & Applications, Macquarie University, Sydney, NSW 2109, Australia (Fax: +61-2/9850-8313, E-mail: brian.orr@mq.edu.au), AU;(2) Macquarie University Visiting Research Fellow, 1998; permanent address: Chemistry Department, Oregon State University, Corvallis, Oregon 97331-9800, USA (Fax: +1-541/737-2062, E-mail: niblerj@chem.orst.edu), US |
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| Abstract: | Optical parametric oscillator (OPO) and amplifier (OPA) devices are useful for spectroscopic sensing of chemical processes in laboratory, industrial, and environmental settings. This is particularly true of nanosecond-pulsed, continuously tunable OPO/OPA systems, for which we survey a variety of instrumental strategies, together with actual spectroscopic measurements. The relative merits of OPO wavelength control by intracavity gratings and by injection seeding are considered. A major innovation comprises an OPO with a ring cavity based on periodically poled lithium niobate (PPLN) and injection-seeded by a single-mode tunable diode laser (TDL). Active cavity control by an ‘intensity dip’ method yields an optical bandwidth ≤0.005 cm-1 (150 MHz), which compares favourably with the performance of advanced grating-tuned OPO/OPA systems. A novel adaptation of this TDL-seeded PPLN OPO employs a compact, inexpensive multimode pump laser, with which it is still possible to obtain continuously tunable single-mode signal output. Cavity ringdown (CRD) spectroscopy also figures prominently, with infrared (IR) CRD spectra from both grating-scanned and TDL-seeded OPOs reported. Finally, a tunable ultraviolet (UV) source, combining a TDL-seeded passive-cavity OPO and a sum-frequency generation stage, is developed for measurements of time-resolved IR-UV double resonance spectra of acetylene and UV laser-induced fluorescence spectra of nitric oxide. Received: 28 March 2000 / Published online: 13 September 2000 |
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| Keywords: | PACS: 33.20.-t 42.62.Fi 42.65.Yj |
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