664 research outputs found
Theoretical investigation of one-dimensional cavities in two-dimensional photonic crystals
We study numerically the features of the resonant peak of one-dimensional
(1-D) dielectric cavities in a two-dimensional (2-D) hexagonal lattice. We use
both the transfer matrix method and the finite difference time-domain (FDTD)
method to calculate the transmission coefficient. We compare the two methods
and discuss their results for the transmission and quality factor Q of the
resonant peak. We also examine the dependence of Q on absorption and losses,
the thickness of the sample and the lateral width of the cavity. The Q- factor
dependence on the width of the source in the FDTD calculations is also given.Comment: 25 pages, 8 figure
Metal-insulator transitions in anisotropic 2d systems
Several phenomena related to the critical behaviour of non-interacting
electrons in a disordered 2d tight-binding system with a magnetic field are
studied. Localization lengths, critical exponents and density of states are
computed using transfer matrix techniques. Scaling functions of isotropic
systems are recovered once the dimension of the system in each direction is
chosen proportional to the localization length. It is also found that the
critical point is independent of the propagation direction, and that the
critical exponents for the localization length for both propagating directions
are equal to that of the isotropic system (approximately 7/3). We also
calculate the critical value of the scaling function for both the isotropic and
the anisotropic system. It is found that the isotropic value equals the
geometric mean of the two anisotropic values. Detailed numerical studies of the
density of states for the isotropic system reveals that for an appreciable
amount of disorder the critical energy is off the band center.Comment: 6 pages RevTeX, 6 figures included, submitted to Physical Review
Two-dimensional photonic crystal polarizer
A novel polarizer made from two-dimensional photonic bandgap materials was
demonstrated theoretically. This polarizer is fundamentally different from the
conventinal ones. It can function in a wide frequency range with high
performance and the size can be made very compact, which renders it useful as a
micropolarizer in microoptics.Comment: 8 pages, RevTex, 4 figure
Spontaneous emission in the near-field of 2D photonic crystals
We show theoretically that photonic crystal membranes cause large variations
in the spontaneous emission rate of dipole emitters, not only inside but also
in the near-field above the membranes. Our three-dimensional finite difference
time-domain calculations reveal an inhibition of more than five times and an
enhancement of more than ten times for the spontaneous emission rate of
emitters with select dipole orientations and frequencies. Furthermore we
demonstrate theoretically, the potential of a nanoscopic emitter attached to
the end of a glass fiber tip as a local probe for mapping the large spatial
variations of the photonic crystal local radiative density of states. This
arrangement is promising for on-command modification of the coupling between an
emitter and the photonic crystal in quantum optical experiments.Comment: 3 pages, 3 figures. Figure 2 colo
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