title: Angular output of hollow, metal-lined, waveguide Raman sensors.
abstract: Hollow, metal-lined waveguides used as gas sensors based on spontaneous Raman scattering are capable of large angular collection. The collection of light from a large solid angle implies the collection of a large number of waveguide modes. An accurate estimation of the propagation losses for these modes is required to predict the total collected Raman power. We report a theory/experimental comparison of the Raman power collected as a function of the solid angle and waveguide length. New theoretical observations are compared with previous theory appropriate only for low-order modes. A cutback experiment is demonstrated to verify the validity of either theory. The angular distribution of Raman light is measured using aluminum and silver-lined waveguides of varying lengths.
authors.affiliation: Office of Research and Development, National Energy Technology Laboratory, Morgantown, West Virginia 26507-0880, USA.
authors.forename: Stephen
authors.initials: S
authors.lastname: Biedrzycki
authors.forename: Michael P
authors.initials: MP
authors.lastname: Buric
authors.forename: Joel
authors.initials: J
authors.lastname: Falk
authors.forename: Steven D
authors.initials: SD
authors.lastname: Woodruff