title: Controlling optical gain in semiconducting polymers with nanoscale chain positioning and alignment.
abstract: We control the chain conformation of a semiconducting polymer by encapsulating it within the aligned nanopores of a silica host. The confinement leads to polarized, low-threshold amplified spontaneous emission from the polymer chains. The polymer enters the porous silica film from only one face and the filling of the pores is therefore graded. As a result, the profile of the index of refraction in the film is also graded, in the direction normal to the pores, so that the composite film forms a low-loss, graded-index waveguide. The aligned polymer chains plus naturally formed waveguide are ideally configured for optical gain, with a threshold for amplified spontaneous emission that is twenty times lower than in comparable unoriented polymer films. Moreover, the optimal conditions for ASE are met in only one spatial orientation and with one polarization. The results show that nanometre-scale control of semiconducting polymer chain orientation and position leads to novel and desirable optical properties.
authors.affiliation: Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095-1569, USA.
authors.forename: Ignacio B
authors.initials: IB
authors.lastname: Martini
authors.forename: Ian M
authors.initials: IM
authors.lastname: Craig
authors.forename: William C
authors.initials: WC
authors.lastname: Molenkamp
authors.forename: Hirokatsu
authors.initials: H
authors.lastname: Miyata
authors.forename: Sarah H
authors.initials: SH
authors.lastname: Tolbert
authors.forename: Benjamin J
authors.initials: BJ
authors.lastname: Schwartz
mesh_terms: D004867:Equipment Design; D019544:Equipment Failure Analysis; D008027:Light; D049329:Nanostructures / Q000737:chemistry*; D036103:Nanotechnology / Q000295:instrumentation*; D055095:Optics and Photonics / Q000295:instrumentation*; D011108:Polymers / Q000737:chemistry*; D012542:Scattering, Radiation; D012666:Semiconductors; D012822:Silicon Dioxide / Q000737:chemistry*
chemical_list: D011108:Polymers; D012822:Silicon Dioxide