Diffraction from carbon nanofiber arrays

Abstract

A square planar photonic crystal composed of carbon nanofibers was fabricated using e-beam lithography and chemical vapor deposition. The diffraction properties of the system were characterized experimentally and compared with theory and numerical simulations. The intensities of the (-1,0) and (-1,-1) diffraction beams were measured as functions of the angles of incidence for both s and p-polarization. The obtained radiation patterns can be explained using a simple ray interference model, but finite-difference time-domain (FDTD) calculations are necessary to reproduce the observed dependence of the scattered radiation intensity on incident laser polarization. We explain this in terms of the aspect ratio of the nanofibers and the excitation of surface plasmon polaritons at the substrate interface.

Electromechanically Tunable Carbon Nanofiber Photonic Crystal

“…2 where the relative intensity change, I, for the (0;- We have shown previously 13 that the absolute intensity is higher for s-polarization than for p-polarization in the static case (by approximately 50%) . This was interpreted, and supported by FTDT simulations, as being a consequence of a higher field intensity at the CNFs with p-polarized light due to the hybridization of surface plasmon polaritons which are mainly p-polarized excitations at the metal electrodes with the surface modes of the CNF lattice.…”

“…This was interpreted, and supported by FTDT simulations, as being a consequence of a higher field intensity at the CNFs with p-polarized light due to the hybridization of surface plasmon polaritons which are mainly p-polarized excitations at the metal electrodes with the surface modes of the CNF lattice. 13 We therefore expect the intensity to increase for p-polarization and decrease for s-polarization on actuation, as This phenomenologically explains the diffracted intensity variation due to actuation. The exact values of  and  are difficult to obtain theoretically since they depend on many (unknown) properties of the VACNFs and the substrate.…”

“…15 We have also shown that the main features of the diffraction properties of the VACNF PC can be modelled using standard diffraction theory but observed polarization-dependent diffraction intensities required a consideration of the form factor of the VACNF array and the role of surface plasmons at the PC-substrate interface to be explained. 13 In this letter we combine these two techniques to characterise tunable VACNF PC.…”

“…The diffraction set-up has been described before 13 and consists of a sample holder with translational and rotational degrees of freedom for calibration and selection of incoming and exiting angles of the light beams.…”

Immersion Lithographic Patterning of Electrospun Nanofibers for Carbon Nanofibrous Microelectrode Arrays

“…Such diffraction and scattering effects can be amplified if the medium consists of multiple materials with large refractive index differences and the characteristic dimension of the material is comparable to the wavelength of the optical light source, which results in poor directivity and limited patterning capability. The typical diameter of electrospun nanofibers is between 100 nm and 500 nm, a range comparable to the wavelengths commonly used for UV lithography, such as i -line of 365 nm and g-line of 405 nm, and therefore provides a challenge for the fabrication of well-defined 3-D naofibrous microstructures [12], [13], [15].…”