63 research outputs found
Antiresonant guiding microstructured optical fibers for sensing applications
A novel refractometric sensor utilizing unique spectral properties of antiresonant-guiding microstructured optical fibers is proposed. The sensor operation is based on the wavelength shift of the transmission spectrum in response to the refractive index change of a sample loaded in the air-holes of the microstructured optical fiber. Refractive index changes on the order of 0.1% can be detected using less than a nanoliter of a sample.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47050/1/340_2005_Article_1888.pd
Effect of an Optical Negative Index Thin Film on Optical Bistability
We investigate nonlinear transmission in a layered structure consisting of a
slab of positive index material (PIM) with Kerr-type nonlinearity and a
sub-wavelength layer of linear negative index material (NIM) sandwiched between
semi-infinite linear dielectrics. We find that a thin layer of NIM leads to
significant changes in the hysteresis width when the nonlinear slab is
illuminated at an angle near that of total internal reflection. Unidirectional
diode-like transmission with enhanced operational range is demonstrated. These
results may be useful for NIMs characterization and for designing novel NIMs
based devices
Tailoring optical nonlinearities via the Purcell effect
We predict that the effective nonlinear optical susceptibility can be
tailored using the Purcell effect. While this is a general physical principle
that applies to a wide variety of nonlinearities, we specifically investigate
the Kerr nonlinearity. We show theoretically that using the Purcell effect for
frequencies close to an atomic resonance can substantially influence the
resultant Kerr nonlinearity for light of all (even highly detuned) frequencies.
For example, in realistic physical systems, enhancement of the Kerr coefficient
by one to two orders of magnitude could be achieved
Wide-band negative permeability of nonlinear metamaterials
We propose a novel way to achieve an exceptionally wide frequency range where metamaterial possesses negative effective permeability. This can be achieved by employing a nonlinear response of metamaterials. We demonstrate that, with an appropriate design, a frequency band exceeding 100% is available for a range of signal amplitudes. Our proposal provides a significant improvement over the linear approach, opening a road towards broadband negative refraction and its applications
Nonlinear atom optics and bright gap soliton generation in finite optical lattices
We theoretically investigate the transmission dynamics of coherent matter
wave pulses across finite optical lattices in both the linear and the nonlinear
regimes. The shape and the intensity of the transmitted pulse are found to
strongly depend on the parameters of the incident pulse, in particular its
velocity and density: a clear physical picture for the main features observed
in the numerical simulations is given in terms of the atomic band dispersion in
the periodic potential of the optical lattice. Signatures of nonlinear effects
due the atom-atom interaction are discussed in detail, such as atom optical
limiting and atom optical bistability. For positive scattering lengths, matter
waves propagating close to the top of the valence band are shown to be subject
to modulational instability. A new scheme for the experimental generation of
narrow bright gap solitons from a wide Bose-Einstein condensate is proposed:
the modulational instability is seeded in a controlled way starting from the
strongly modulated density profile of a standing matter wave and the solitonic
nature of the generated pulses is checked from their shape and their
collisional properties
High-Directional Wave Propagation in Periodic Gain/Loss Modulated Materials
Amplification/attenuation of light waves in artificial materials with a
gain/loss modulation on the wavelength scale can be sensitive to the
propagation direction. We give a numerical proof of the high anisotropy of the
gain/loss in two dimensional periodic structures with square and rhombic
lattice symmetry by solving the full set of Maxwell's equations using the
finite difference time domain method. Anisotropy of amplification/attenuation
leads to the narrowing of the angular spectrum of propagating radiation with
wavevectors close to the edges of the first Brillouin Zone. The effect provides
a novel and useful method to filter out high spatial harmonics from noisy
beams
Advances and new applications using the acousto-optic effect in optical fibers
This work presents a short review of the current research on the acousto-optic mechanism applied to optical fibers. The role of the piezoelectric element and the acousto-optic modulator in the excitation of flexural and longitudinal acoustic modes in the frequency range up to 1.2 MHz is highlighted. A combination of the finite elements and the transfer matrix methods is used to simulate the interaction of the waves with Bragg and long period gratings. Results show a very good agreement with experimental data. Recent applications such as the writing of gratings under the acoustic excitation and a novel viscometer sensor based on the acousto-optic mechanism are discussed
Photonic metamaterials
The invention of metamaterials prompts reconsideratiou of a number of fundamental physical phenomena and enables a variety of unique properties and functionalities, These include negative refractive index, magnetism at optical frequencies, sub-wavelength resolution, backward phase matching conditions for nonlinear optical processes, and even rendering objects invisible - cloaking. In this brief review, recent progress in basic theory, design, fabrication, characterization, and potential applications of optical metamaterials is discussed
Generalized Analytical Solutions for Nonlinear Positive-Negative Index Couplers
We find and analyze a generalized analytical solution for nonlinear wave propagation in waveguide couplers with opposite signs of the linear refractive index, nonzero phase mismatch between the channels, and arbitrary nonlinear coefficients
- …