Guiding and Confining Light in Nanoporous Cu4O3-C Composite Thin Films
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0964-R03-20
Guiding and Confining Light in Nanoporous Cu4O3-C Composite Thin Films Mahua Das and S. A. Shivashankar Materials Research Centre, Indian Institute of Science, C.V. Raman Avenue, Bangalore, 560012, India
ABSTRACT Nanoporous Cu4O3 – C composite thin films with spherical and bicontinuous elongated pore structure have been grown on stainless steel substrates by metalorganic chemical vapour deposition technique using a single source tetranuclear metalorganic complex as precursor. The guiding and confinement of light in these quasi-periodic structures has been investigated by glancing incidence (75o) infrared spectroscopy at room temperature. The transmittance spectra of these films between wave number 10000 – 400 cm-1 reveal light confinement modes in photonic band gap between 6127- 8839 cm-1 and propagation modes between 5094- 400 cm-1.
INTRODUCTION The propagation of light in complex dielectric media, namely structures with an index of refraction that has variations on a length scale that is roughly comparable to the wavelength of the incident light, is a rich and fascinating phenomenon. Such complex media strongly scatter light. In particular, if a complex material is assembled in a periodic way we obtain a crystal-like structure that under appropriate conditions may exhibit energy bands, i.e., energy regions in which light can propagate separated by regions in which light cannot propagate and hence called photonic band gaps [1,2]. With their remarkable capabilities of localizing and guiding radiation, photonic crystals can be used to create miniature high reflectance mirrors [3], which only reflect light over the same wavelength range as the band gap, as well as narrow waveguides [4], filters [5], and microlasers [6]. They have further opened a whole new chapter in nonlinear optics [7] suggesting a conceptually new architecture for nonlinear optical materials exhibiting alternative schemes for amplification [8], for nonclassical light generation [9], enhanced photon-photon correlation [10, 11], artificial anisotropy and engineered point-group symmetry [12]. Photonic crystals have finally spurred the investigation of interesting new phenomena such as superprism effects [13], negative refraction [14], negative refraction of sound waves [15], quenching of spontaneous [16] and stimulated [17] emission, refractive index enhancement [18], just to mention a few. In its simplest version photonic crystal is created by introducing air holes into a solid medium having a high refractive index. In cases studied so far, the distribution of air holes is uniform laterally or along the thickness of the film. In the present study, we grow nanoporous films of Cu4O3-C composite where pores are randomly distributed laterally along the films. In these films, a periodically modulated absorption caused by the near periodicity in groves at the micrometer length entails an inevitable spatial modulation of dispersion, i.e. of index contrast to open a band gap. Grazing incidence infrared spectroscopy was used to probe the locali
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