Browsing by Subject "crystallization"

Now showing 1 - 3 of 3

Open Access
Compact wavelength de-multiplexer design using slow light regime of photonic crystal waveguides
(Optical Society of American (OSA), 2011) Akosman, A.E.; Mutlu, M.; Kurt H.; Özbay, Ekmel
We demonstrate the operation of a compact wavelength demultiplexer using cascaded single-mode photonic crystal waveguides utilizing the slow light regime. By altering the dielectric filling factors of each waveguide segment, we numerically and experimentally show that different frequencies are separated at different locations along the waveguide. In other words, the beams of different wavelengths are spatially dropped along the transverse to the propagation direction. We numerically verified the spatial shifts of certain wavelengths by using the two-dimensional finite-difference time-domain method. The presented design can be extended to de-multiplex more wavelengths by concatenating additional photonic crystal waveguides with different filling factors. © 2011 Optical Society of America.
Open Access
Electrochemical synthesis of mesoporous gold films toward mesospace-stimulated optical properties
(Nature Publishing Group, 2015) Li C.; Dag Ö.; Dao, T.D.; Nagao, T.; Sakamoto, Y.; Kimura, T.; Terasaki O.; Yamauchi, Y.
Mesoporous gold (Au) films with tunable pores are expected to provide fascinating optical properties stimulated by the mesospaces, but they have not been realized yet because of the difficulty of controlling the Au crystal growth. Here, we report a reliable soft-templating method to fabricate mesoporous Au films using stable micelles of diblock copolymers, with electrochemical deposition advantageous for precise control of Au crystal growth. Strong field enhancement takes place around the center of the uniform mesopores as well as on the walls between the pores, leading to the enhanced light scattering as well as surface-enhanced Raman scattering (SERS), which is understandable, for example, from Babinet principles applied for the reverse system of nanoparticle ensembles. © 2015 Macmillan Publishers Limited. All rights reserved.
Open Access
Unidirectional transmission in photonic-crystal gratings at beam-type illumination
(Optical Society of American (OSA), 2010) Cakmak, A.O.; Colak, E.; Serebryannikov, A.E.; Özbay, Ekmel
Unidirectional transmission is studied theoretically and experimentally for the gratings with one-side corrugations (non-symmetric gratings), which are based on two-dimensional photonic crystals composed of alumina rods. The unidirectional transmission appears at a fixed angle of incidence as a combined effect of the peculiar dispersion features of the photonic crystal and the properly designed corrugations. It is shown that the basic unidirectional transmission characteristics, which are observed at a plane-wave illumination, are preserved at Gaussian-beam and horn antenna illuminations. The main attention is paid to the single-beam unidirectional regime, which is associated with the strong directional selectivity arising due to the first negative diffraction order. An additional degree of freedom for controlling the transmission of the electromagnetic waves is obtained by making use of the asymmetric corrugations at the photonic crystal interface. © 2010 Optical Society of America.