33 research outputs found
Cavity quantum electrodynamics with three-dimensional photonic bandgap crystals
This paper gives an overview of recent work on three-dimensional (3D)
photonic crystals with a "full and complete" 3D photonic band gap. We review
five main aspects: 1) spontaneous emission inhibition, 2) spatial localization
of light within a tiny nanoscale volume (aka "a nanobox for light"), 3) the
introduction of a gain medium leading to thresholdless lasers, 4) breaking of
the weak-coupling approximation of cavity QED, both in the frequency and in the
time-domain, 5) decoherence, in particular the shielding of vacuum fluctuations
by a 3D photonic bandgap. In addition, we list and evaluate all known photonic
crystal structures with a demonstrated 3D band gap.Comment: 21 pages, 6 figures, 2 tables, Chapter 8 in "Light Localisation and
Lasing: Random and Pseudorandom Photonic Structures", Eds. M. Ghulinyan and
L. Pavesi (Cambridge University Press, Cambridge, 2015, ISBN
978-1-107-03877-6
Method to pattern etch masks in two inclined planes for three-dimensional nano- and microfabrication
Design of a 3D photonic band gap cavity in a diamond-like inverse woodpile photonic crystal
We theoretically investigate the design of cavities in a three-dimensional
(3D) inverse woodpile photonic crystal. This class of cubic diamond-like
crystals has a very broad photonic band gap and consists of two perpendicular
arrays of pores with a rectangular structure. The point defect that acts as a
cavity is centred on the intersection of two intersecting perpendicular pores
with a radius that differs from the ones in the bulk of the crystal. We have
performed supercell bandstructure calculations with up to
unit cells. We find that up to five isolated and dispersionless bands appear
within the 3D photonic band gap. For each isolated band, the electric-field
energy is localized in a volume centred on the point defect, hence the point
defect acts as a 3D photonic band gap cavity. The mode volume of the cavities
resonances is as small as 0.8 (resonance wavelength cubed),
indicating a strong confinement of the light. By varying the radius of the
defect pores we found that only donor-like resonances appear for smaller defect
radius, whereas no acceptor-like resonances appear for greater defect radius.
From a 3D plot of the distribution of the electric-field energy density we
conclude that peaks of energy found in sharp edges situated at the point
defect, similar to how electrons collect at such features. This is different
from what is observed for cavities in non-inverted woodpile structures. Since
inverse woodpile crystals can be fabricated from silicon by CMOS-compatible
means, we project that single cavities and even cavity arrays can be realized,
for wavelength ranges compatible with telecommunication windows in the near
infrared.Comment: 11 figure
Method to make a single-step etch mask for 3D monolithic nanostructures
Current nanostructure fabrication by etching is usually limited to planar
structures as they are defined by a planar mask. The realisation of
three-dimensional (3D) nanostructures by etching requires technologies beyond
planar masks. We present a method to fabricate a 3D mask that allows to etch
three-dimensional monolithic nanostructures by using only CMOS-compatible
processes. The mask is written in a hard-mask layer that is deposited on two
adjacent inclined surfaces of a Si wafer. By projecting in single step two
different 2D patterns within one 3D mask on the two inclined surfaces, the
mutual alignment between the patterns is ensured. Thereby after the mask
pattern is defined, the etching of deep pores in two oblique directions yields
a three-dimensional structure in Si. As a proof of concept we demonstrate 3D
mask fabrication for three-dimensional diamond-like photonic band gap crystals
in silicon. The fabricated crystals reveal a broad stop gap in optical
reflectivity measurements. We propose how 3D nanostructures with five different
Bravais lattices can be realised, namely cubic, tetragonal, orthorhombic,
monoclinic, and hexagonal, and demonstrate a mask for a 3D hexagonal crystal.
We also demonstrate the mask for a diamond-structure crystal with a 3D array of
cavities. In general, the 2D patterns for the different surfaces can be
completely independent and still be in perfect mutual alignment. Indeed, we
observe an alignment accuracy of better than 3.0 nm between the 2D mask
patterns on the inclined surfaces, which permits one to etch well-defined
monolithic 3D nanostructures.Comment: 18 pages, 10 figure
Signature of a three-dimensional photonic band gap observed on silicon inverse woodpile photonic crystals
We have studied the reflectivity of CMOS-compatible three-dimensional silicon
inverse woodpile photonic crystals at near-infrared frequencies.
Polarization-resolved reflectivity spectra were obtained from two orthogonal
crystal surfaces corresponding to 1.88 pi sr solid angle. The spectra reveal
broad peaks with high reflectivity up to 67 % that are independent of the
spatial position on the crystals. The spectrally overlapping reflectivity peaks
for all directions and polarizations form the signature of a broad photonic
band gap with a relative bandwidth up to 16 %. This signature is supported with
stopgaps in plane wave bandstructure calculations and with the frequency region
of the expected band gap.Comment: 9 pages, 5 figure
Observation of sub-Bragg diffraction of waves in crystals
We investigate the diffraction conditions and associated formation of
stopgaps for waves in crystals with different Bravais lattices. We identify a
prominent stopgap in high-symmetry directions that occurs at a frequency below
the ubiquitous first-order Bragg condition. This sub-Bragg diffraction
condition is demonstrated by reflectance spectroscopy on two-dimensional
photonic crystals with a centred rectangular lattice, revealing prominent
diffraction peaks for both the sub-Bragg and first-order Bragg condition. These
results have implications for wave propagation in 2 of the 5 two-dimensional
Bravais lattices and 7 out of 14 three-dimensional Bravais lattices, such as
centred rectangular, triangular, hexagonal and body-centred cubic
ANALISIS BANJIR RANCANGAN DENGAN METODE HSS NAKAYASU PADA BENDUNGAN GINTUNG
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perlu dikembangkan perhitungan banjir rancangan dengan metode HSS Nakayasu. Perhitungan
dengan menggunaan data hujan. Pada penelitian ini digunakan 18 Pos stasiun penangkar hujan
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hujan harian maksimum tahunan. Data curah hujan yang disaring memilki tingkat kepercayaan
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terlebih dahulu dilakukan ana/isa frekuensi dan penetapan sebaran data curah hujan kemudian
diuji dengan chi-kuadrat. Distribusi yang sesuai adalah distribusi Log Pearson Type III. Dari
hasil ana/isa debit banjir rancangan, untuk merencanakan bendungan digunakan debit banjir
kala ulang Ql000 = 289,348 m3/dt
The role of fabrication deviations on the photonic band gap of 3D inverse woodpile nanostructures
In this report the effects of unintended deviations from ideal inverse
woodpile photonic crystals on the band gap are discussed. These deviations
occur during the nanofabrication of the crystal. By computational analyses it
is shown that the band gap of this type of crystal is robust to most types of
deviations that relate to the radii, position and angular alignment of the
pores. However, the photonic band gap is very sensitive to tapering of the
pores, i.e., conically shaped pores instead of cylindrical pores. To obtain
three-dimensional inverse woodpile photonic crystals with a large volume, our
work shows that with modern fabrication performances, tapering contributes most
significantly to a reduction in the photonic strength of inverse woodpile
photonic crystals.Comment: 36 pages, 15 figure
Angular redistribution of near-infrared emission from quantum dots in 3D photonic crystals
We study the angle-resolved spontaneous emission of near-infrared light
sources in 3D photonic crystals over a wavelength range from 1200 to 1550 nm.
To this end PbSe quantum dots are used as light sources inside titania inverse
opal photonic crystals. Strong deviations from the Lambertian emission profile
are observed. An attenuation of 60 % is observed in the angle dependent radiant
flux emitted from the samples due to photonic stop bands. At angles that
correspond to the edges of the stop band the emitted flux is increased by up to
34 %. This increase is explained by the redistribution of Bragg-diffracted
light over the available escape angles. The results are quantitatively
explained by an expanded escape-function model. This model is based on
diffusion theory and adapted to photonic crystals using band structure
calculations. Our results are the first angular redistributions and escape
functions measured at near-infrared, including telecom, wavelengths. In
addition, this is the first time for this model to be applied to describe
emission from samples that are optically thick for the excitation light and
relatively thin for the photoluminesence light.Comment: 24 pages, 8 figures (current format = single column, double spaced