title: Mixed two- and three-photon absorption in bulk rutile (TiO2) around 800 nm.
abstract: We observe mixed two- and three-photon absorption in bulk rutile (TiO2) around 800 nm using the open aperture Z-scan technique. We fit the data with an extended model that includes multiphoton absorption, beam quality, and ellipticity. The extracted two- and three-photon absorption coefficients are below 1 mm/GW and 2 mm3/GW2, respectively. We observe negligible two-photon absorption for 813-nm light polarized along the extraordinary axis. We measure the nonlinear index of refraction and obtain two-photon nonlinear figures of merit greater than 1.1 at 774 nm and greater than 12 at 813 nm. Similarly, we obtain three-photon figures of merit that allow operational intensities up to 0.57 GW/mm2. We conclude that rutile is a promising material for all-optical switching applications around 800 nm.
authors.affiliation: School of Engineering and Applied Sciences, Harvard University, 9 Oxford Street, Cambridge, Massachusetts 02138, USA.
authors.forename: Christopher C
authors.initials: CC
authors.lastname: Evans
authors.forename: Jonathan D B
authors.initials: JD
authors.lastname: Bradley
authors.forename: Erwin A
authors.initials: EA
authors.lastname: Martí-Panameño
authors.forename: Eric
authors.initials: E
authors.lastname: Mazur
mesh_terms: D008027:Light; D008422:Materials Testing; D017785:Photons; D012031:Refractometry; D012542:Scattering, Radiation; D014025:Titanium / Q000737:chemistry*
chemical_list: C009495:titanium dioxide; D014025:Titanium