Cavity Ring-down Spectroscopy

Cavity Ring-down Spectroscopy

Research Opportunity:

In recent years, cavity ring-down spectroscopy (CRDS) has been employed to measure the optical absorption of gases with extremely high sensitivity by utilizing the photon decay time in a high-finesse optical cavity as the absorption sensitive observable. We are developing a novel implementation of CRDS, termed evanescent wave cavity ring-down spectroscopy (EW-CRDS), that extends the technique to surfaces and condensed media. EW-CRDS utilizes novel optical cavity designs that employ total internal reflection (TIR) at ultra-smooth surfaces which have a root-mean square surface roughness of typically less than an atomic diameter. Applications for two cavity designs are currently being explored. The miniature, monolithic TIR-ring cavity, which employs photon tunneling for excitation and detection of cavity modes, provides broad spectral bandwidth thereby allowing multiple surface species to be probed with a single device. A monolithic folded cavity has also been developed which has a narrow bandwidth but simplified operation. Extreme sub-monolayer detection sensitivity has been demonstrated with both designs, along with the ability to determine molecular orientation at the surface. EW-CRDS provides a new tool for fundamental studies of surface chemistry and physics, while forming the basis for a new chemical sensing technology. Over the next few years, we will be combining the sensitivity of EW-CRDS with the selectivity of molecular recognition chemistry by functionalizing the ultra-smooth TIR surfaces of EW-CRDS resonators. We will also explore the formation, structure, and application of nanostructured EW-CRDS surfaces. Collaborations with industrial partners, national laboratories, and academia are expanding the breath and future of our research. Challenging experimental and theoretical postdoctoral projects abound, including studies of the surface chemistry and physics of small molecules or large systems showing molecular recognition properties (including biological systems), surface optical activity, and optical properties of nanostructures.

Selected Publications:

1. A. C. R. Pipino, "Monolithic, folded resonator for evanescent wave cavity ring-down spectroscopy", Appl. Opt. March 20, 2000.

2. A. C. R. Pipino, "Ultra-sensitive surface spectroscopy with a miniature optical resonator", Phys. Rev. Lett. 83 (15), 3093, (1999).

3. A. C. R. Pipino, J. W. Hudgens, and R. E. Huie, "Evanescent wave cavity ring-down spectroscopy", Chem. Phys. Lett. 280, 104, (1997).

4. A. C. R. Pipino, J. W. Hudgens, and R. E. Huie, "Evanescent wave cavity ring-down spectroscopy with a total-internal-reflection minicavity", Rev. Sci. Instrum. 68 (8), 2978, (1997).

5. A.C.R. Pipino, R.P. Van Duyne, and G.C. Schatz, "Surface-enhanced second harmonic diffraction: Experimental verification of selective enhancement", Phys. Rev. B 53, 4162 (1996).

6. A. C. R. Pipino, G.C. Schatz, and RP Van Duyne, "A rigorous electrodynamic model for periodic structure formation during UV-laser-induced metal atom deposition", Chem. Phys. Lett., 237, 137 (1995).

7. A. C. R. Pipino and G.C. Schatz, "Surface profile dependence of photon-plasmon-polariton coupling at a corrugated silver surface", J. Opt. So. Am. B 11, 2036 (1994).

8. A.C.R. Pipino, G.C. Schatz, and RP Van Duyne, "Surface-enhanced second harmonic diffraction: Selective enhancement by spatial harmonics", Phys. Rev. B 49, 8320, (1994).

Patents:

1) U. S. # 5,835,231

2) U. S. # 5,986,768

3) U. S. # 5,943,136

For more information, contact Andrew Pipino at andrew.pipino@nist.gov

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Last Updated on: 2/25/04