15 research outputs found
Investigation of defect cavities formed in three-dimensional woodpile photonic crystals
We report the optimisation of optical properties of single defects in
three-dimensional (3D) face-centred-cubic (FCC) woodpile photonic crystal (PC)
cavities by using plane-wave expansion (PWE) and finite-difference time-domain
(FDTD) methods. By optimising the dimensions of a 3D woodpile PC, wide photonic
band gaps (PBG) are created. Optical cavities with resonances in the bandgap
arise when point defects are introduced in the crystal. Three types of single
defects are investigated in high refractive index contrast (Gallium
Phosphide-Air) woodpile structures and Q-factors and mode volumes ()
of the resonant cavity modes are calculated. We show that, by introducing an
air buffer around a single defect, smaller mode volumes can be obtained. We
demonstrate high Q-factors up to 700000 and cavity volumes down to
. The estimates of and are then used to
quantify the enhancement of spontaneous emission and the possibility of
achieving strong coupling with nitrogen-vacancy (NV) colour centres in diamond.Comment: 12 pages, 11 figure
Evidence of near-infrared partial photonic bandgap in polymeric rod-connected diamond structures
We present the simulation, fabrication, and optical characterization of
low-index polymeric rod-connected diamond (RCD) structures. Such complex
three-dimensional photonic crystal structures are created via direct laser
writing by two-photon polymerization. To our knowledge, this is the first
measurement at near-infrared wavelengths, showing partial photonic bandgaps for
this structure. We characterize structures in transmission and reflection using
angular resolved Fourier image spectroscopy to visualize the band structure.
Comparison of the numerical simulations of such structures with the
experimentally measured data show good agreement for both P- and
S-polarizations
Microstructure-Stabilized Blue Phase Liquid Crystals
We show that micron-scale two-dimensional (2D) honeycomb microwells can
significantly improve the stability of blue phase liquid crystals (BPLCs).
Polymeric microwells made by direct laser writing improve various features of
the blue phase (BP) including a dramatic extension of stable temperature range
and a large increase both in reflectivity and thermal stability of the
reflective peak wavelength. These results are mainly attributed to the
omni-directional anchoring of the isotropically oriented BP molecules at the
polymer walls of the hexagonal microwells and at the top and bottom substrates.
This leads to an omni-directional stabilization of the entire BPLC system. This
study not only provides a novel insight into the mechanism for the BP formation
in the 2D microwell but also points to an improved route to stabilize BP using
2D microwell arrays.Comment: 16 pages, 5 figure
Investigation of defect cavities formed in three-dimensional woodpile photonic crystals
We report the optimisation of optical properties of single defects in three-dimensional (3D) face-centred-cubic (FCC) woodpile photonic crystal (PC) cavities by using plane-wave expansion (PWE) and finite-difference time-domain (FDTD) methods. By optimising the dimensions of a 3D woodpile PC, wide photonic band gaps (PBG) are created. Optical cavities with resonances in the bandgap arise when point defects are introduced in the crystal. Three types of single defects are investigated in high refractive index contrast (Gallium Phosphide-Air) woodpile structures and Q-factors and mode volumes (Veff) of the resonant cavity modes are calculated. We show that, by introducing an air buffer around a single defect, smaller mode volumes can be obtained. We demonstrate high Q-factors up to 700000 and cavity volumes down to Veff<0.2(λ/n)3. The estimates of Q and Veff are then used to quantify the enhancement of spontaneous emission and the possibility of achieving strong coupling with nitrogen-vacancy (NV) colour centres in diamond
Strongly Confining Light with Air-Mode Cavities in Inverse Rod-Connected Diamond Photonic Crystals
Three-dimensional dielectric optical crystals with a high index show a complete photonic bandgap (PBG), blocking light propagation in all directions. We show that this bandgap can be used to trap light in low-index defect cavities, leading to strongly enhanced local fields. We compute the band structure and optimize the bandgap of an inverse 3D rod-connected diamond (RCD) structure, using the plane-wave expansion (PWE) method. Selecting a structure with wide bandgap parameters, we then add air defects at the center of one of the high-index rods of the crystal and study the resulting cavity modes by exciting them with a broadband dipole source, using the finite-difference time-domain (FDTD) method. Various defect shapes were studied and showed extremely small normalized mode volumes (Veff) with long cavity storage times (quality factor Q). For an air-filled spherical cavity of radius 0.1 unit-cell, a record small-cavity mode volume of Veff~2.2 × 10−3 cubic wavelengths was obtained with Q~3.5 × 106
Strongly Confining Light with Air-Mode Cavities in Inverse Rod-Connected Diamond Photonic Crystals
Three-dimensional dielectric optical crystals with a high index show a complete photonic bandgap (PBG), blocking light propagation in all directions. We show that this bandgap can be used to trap light in low-index defect cavities, leading to strongly enhanced local fields. We compute the band structure and optimize the bandgap of an inverse 3D rod-connected diamond (RCD) structure, using the plane-wave expansion (PWE) method. Selecting a structure with wide bandgap parameters, we then add air defects at the center of one of the high-index rods of the crystal and study the resulting cavity modes by exciting them with a broadband dipole source, using the finite-difference time-domain (FDTD) method. Various defect shapes were studied and showed extremely small normalized mode volumes (Veff) with long cavity storage times (quality factor Q). For an air-filled spherical cavity of radius 0.1 unit-cell, a record small-cavity mode volume of Veff~2.2 × 10−3 cubic wavelengths was obtained with Q~3.5 × 106