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Golden spiral photonic crystal fiber: polarization and dispersion properties
A golden spiral photonic crystal fiber (GS-PCF) design is presented in which air holes are arranged in a spiral pattern governed by the golden ratio, where the design has been inspired by the optimal arrangement of seeds found in nature. The birefringence and polarization properties of this fiber are analyzed using a vectorial finite-element method. The fiber that is investigated shows a large modal birefringence peak value of 0.016 at an operating wavelength of 1.55 μm and exhibits highly tuneable dispersion with multiple zero dispersion wavelengths and also large normal dispersion. The GS-PCF design has identical circular air holes that potentially simplify fabrication. In light of its properties, the GS-PCF could have application as a highly birefringent fiber and in nonlinear optics, and moreover the 2D chiral nature of the pattern could yield exotic properties
Efficient Terahertz Generation in Triply Resonant Nonlinear Photonic Crystal Microcavities
We propose a scheme for efficient cavity-enhanced nonlinear THz generation
via difference-frequency generation (DFG) processes using a triply resonant
system based on photonic crystal cavities. We show that high nonlinear overlap
can be achieved by coupling a THz cavity to a doubly-resonant,
dual-polarization near-infrared (e.g. telecom band) photonic-crystal nanobeam
cavity, allowing the mixing of three mutually orthogonal fundamental cavity
modes through a chi(2) nonlinearity. We demonstrate through coupled-mode theory
that complete depletion of the pump frequency - i.e., quantum-limited
conversion - is possible in an experimentally feasible geometry, with the
operating output power at the point of optimal total conversion efficiency
adjustable by varying the mode quality (Q) factors.Comment: 8 pages, 3 figure
Experimental Confirmation of the General Solution to the Multiple Phase Matching Problem
We recently described a general solution to the phase matching problem that
arises when one wishes to perform an arbitrary number of nonlinear optical
processes in a single medium [PRL 95 (2005) 133901]. Here we outline in detail
the implementation of the solution for a one dimensional photonic quasicrystal
which acts as a simultaneous frequency doubler for three independent optical
beams. We confirm this solution experimentally using an electric field poled
KTiOPO crystal. In optimizing the device, we find - contrary to common
practice - that simple duty cycles of 100% and 0% may yield the highest
efficiencies, and show that our device is more efficient than a comparable
device based on periodic quasi-phase-matching
Designing Illumination Lenses and Mirrors by the Numerical Solution of Monge-Amp\`ere Equations
We consider the inverse refractor and the inverse reflector problem. The task
is to design a free-form lens or a free-form mirror that, when illuminated by a
point light source, produces a given illumination pattern on a target. Both
problems can be modeled by strongly nonlinear second-order partial differential
equations of Monge-Amp\`ere type. In [Math. Models Methods Appl. Sci. 25
(2015), pp. 803--837, DOI: 10.1142/S0218202515500190] the authors have proposed
a B-spline collocation method which has been applied to the inverse reflector
problem. Now this approach is extended to the inverse refractor problem. We
explain in depth the collocation method and how to handle boundary conditions
and constraints. The paper concludes with numerical results of refracting and
reflecting optical surfaces and their verification via ray tracing.Comment: 16 pages, 6 figures, 2 tables; Keywords: Inverse refractor problem,
inverse reflector problem, elliptic Monge-Amp\`ere equation, B-spline
collocation method, Picard-type iteration; OCIS: 000.4430, 080.1753,
080.4225, 080.4228, 080.4298, 100.3190. Minor revision: two typos have been
corrected and copyright note has been adde
Bridging the Mid-Infrared-to-Telecom Gap with Silicon Nanophotonic Spectral Translation
Expanding far beyond traditional applications in optical interconnects at
telecommunications wavelengths, the silicon nanophotonic integrated circuit
platform has recently proven its merits for working with mid-infrared (mid-IR)
optical signals in the 2-8 {\mu}m range. Mid-IR integrated optical systems are
capable of addressing applications including industrial process and
environmental monitoring, threat detection, medical diagnostics, and free-space
communication. Rapid progress has led to the demonstration of various silicon
components designed for the on-chip processing of mid-IR signals, including
waveguides, vertical grating couplers, microcavities, and electrooptic
modulators. Even so, a notable obstacle to the continued advancement of
chip-scale systems is imposed by the narrow-bandgap semiconductors, such as
InSb and HgCdTe, traditionally used to convert mid-IR photons to electrical
currents. The cryogenic or multi-stage thermo-electric cooling required to
suppress dark current noise, exponentially dependent upon the ratio Eg/kT, can
limit the development of small, low-power, and low-cost integrated optical
systems for the mid-IR. However, if the mid-IR optical signal could be
spectrally translated to shorter wavelengths, for example within the
near-infrared telecom band, photodetectors using wider bandgap semiconductors
such as InGaAs or Ge could be used to eliminate prohibitive cooling
requirements. Moreover, telecom band detectors typically perform with higher
detectivity and faster response times when compared with their mid-IR
counterparts. Here we address these challenges with a silicon-integrated
approach to spectral translation, by employing efficient four-wave mixing (FWM)
and large optical parametric gain in silicon nanophotonic wires
Parabolic pulse generation with active or passive dispersion decreasing optical fibers
We experimentally demonstrate the possibility to generate
parabolic pulses via a single dispersion decreasing optical fiber with normal
dispersion. We numerically and experimentally investigate the influence of
the dispersion profile, and we show that a hybrid configuration combining
dispersion decrease and gain has several benefits on the parabolic generated
pulses
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