Browsing by Subject "Group velocities"

Now showing 1 - 4 of 4

Open Access
Dual-frequency division de-multiplexer based on cascaded photonic crystal waveguides
(Elsevier, 2012-02-28) Akosman, Ahmet E.; Mutlu, Mehmet; Kurt, H.; Özbay, Ekmel
A dual-frequency division de-multiplexing mechanism is demonstrated using cascaded photonic crystal waveguides with unequal waveguide widths. The de-multiplexing mechanism is based on the frequency shift of the waveguide bands for the unequal widths of the photonic crystal waveguides. The modulation in the waveguide bands is used for providing frequency selectivity to the system. The slow light regime of the waveguide bands is utilized for extracting the desired frequency bands from a wider photonic crystal waveguide that has a relatively larger group velocity than the main waveguide for the de-multiplexed frequencies. In other words, the wider spatial distribution of the electric fields in the transverse direction of the waveguide for slow light modes is utilized in order to achieve the dropping of the modes to the output channels. The spectral and spatial de-multiplexing features are numerically verified. It can be stated that the presented mechanism can be used to de-multiplex more than two frequency intervals by cascading new photonic crystal waveguides with properly selected widths.
Open Access
Lasing in a Slow Plasmon Moiré Cavity
(American Chemical Society, 2015) Karademir, E.; Balci, S.; Kocabas, C.; Aydınlı, Atilla
We report on lasing from dye-based excitons coupled to slow plasmon states inside metallic Moiré cavities. Surface plasmon polaritons (SPPs) inside the cavity were slowed down to a maximum group velocity of 0.3c. Varying the modulation of the Moiré cavity, we tune the output wavelength of the plasmonic laser by varying the fast modulation period of the Moiré cavity. This work opens a new way to study SPP-matter interaction dynamics and plasmonic lasing with Bragg cavity confined slow plasmons.
Open Access
Slowing down surface plasmons on a Moiré surface
(The American Physical Society, 2009-02) Kocabaş, Aşkın; Şenlik, S. Seçkin; Aydınlı, Atilla
We have demonstrated slow propagation of surface plasmons on metallic Moiré surfaces. The phase shift at the node of the Moiré surface localizes the propagating surface plasmons and adjacent nodes form weakly coupled plasmonic cavities. Group velocities around vg=0.44c at the center of the coupled cavity band and almost a zero group velocity at the band edges are observed. A tight binding model is used to understand the coupling behavior. Furthermore, the sinusoidally modified amplitude about the node suppresses the radiation losses and reveals a relatively high quality factor (Q=103).
Open Access
Slowing surface plasmon polaritons on plasmonic coupled cavities by tuning grating grooves
(American Institute of Physics, 2010-09) Balcı, Sinan; Kocabaş, Aşkın; Kocabaş, Coşkun; Aydınlı, Atilla
We investigate slow surface plasmon polaritons (SPPs) in plasmonic waveguiding bands formed by coupled plasmonic cavities on Moiŕ surfaces. We demonstrate controlling the group velocity and dispersion of the SPPs by varying the depth of the plasmonic Bragg grating groove. Changing the grating depth results in modification of coupling coefficients between the cavities and hence the SPPs group velocity is altered. Variation in the group velocity and dispersion of SPPs can be measured with polarization dependent spectroscopic reflection measurements. Dispersion of SPPs has been calculated by finite-difference time-domain method in agreement with the experimental data.