134 research outputs found
Ultra high-Q photonic crystal nanocavity design: The effect of a low-epsilon slab material
We analyze the influence of the dielectric constant of the slab on the
quality factor (Q) in slab photonic crystal cavities with a minimized vertical
losses model. The higher value of Q in high-epsilon cavity is attributed to the
lower mode frequency. The Q ratio in a high-epsilon (silicon) vs. low-epsilon
(diamond) slab is examined as a function of mode volume (Vm). The mode volume
compensation technique is discussed. Finally, diamond cavity design is
addressed. The analytical results are compared to 3D FDTD calculations. In a
double heterostructure design, a Q=2.6*10^5 is obtained. The highest Q=1.3*10^6
with Vm=1.77*(lambda/n)^3 in a local width modulation design is derived.Comment: 8 pages, 6 figure
Modal analysis of semiconductor lasers with nonplanar mirrors
We present a formalism for analyzing laser resonators which possess nonplanar mirrors and lateral waveguiding [e.g., an unstable resonator semiconductor laser (URSL)]. The electric field is expanded in lateral modes of the complex-index waveguide and is required to reproduce itself after, one roundtrip of the cavity. We show how the waveguide modes, their gain and loss, and hence the criterion for truncation of the infinite set of modes can be derived from the Green's function of the one-dimensional eigenvalue equation for the waveguide. Examples are presented for three cases of interest - a purely gain-guided URSL, an index-guided URSL, and a gain-guided tilted-mirror resonator. We compare theoretical calculations to previous experiments
Triangular nanobeam photonic cavities in single crystal diamond
Diamond photonics provides an attractive architecture to explore room
temperature cavity quantum electrodynamics and to realize scalable multi-qubit
computing. Here we review the present state of diamond photonic technology. The
design, fabrication and characterization of a novel triangular cross section
nanobeam cavity produced in a single crystal diamond is demonstrated. The
present cavity design, based on a triangular cross section allows vertical
confinement and better signal collection efficiency than that of slab-based
nanocavities, and eliminates the need for a pre-existing membrane. The nanobeam
is fabricated by Focused-Ion-Beam (FIB) patterning. The cavity is characterized
by a confocal photoluminescence. The modes display quality factors of Q ~220
and are deviated in wavelength by only ~1.7nm from the NV- color center zero
phonon line (ZPL). The measured results are found in good agreement with 3D
Finite-Difference-Time-Domain (FDTD) calculations. A more advanced cavity
design with Q=22,000 is modeled, showing the potential for high-Q
implementations using the triangular cavity design. The prospects of this
concept and its application to spin non-demolition measurement and quantum
computing are discussed.Comment: 18 pages,7 figure
Saturable nonlinear dielectric waveguide with applications to broad-area semiconductor lasers
Self-focusing in a passive dielectric waveguide with a saturable nonlinearity is studied. The eigensolutions constitute a good approximation to the lateral modes of broad-area semiconductor lasers under low-duty-cycle pulsed conditions. The laser modes are predicted to consist of adjacent filaments coupled in phase, leading to a single-lobed far field, and to be stable with increased current injection above saturation intensity. The ultimate filament spacing is inversely proportional to the threshold gain, and thus wider filaments are expected in low-threshold broad-area lasers
Self-stabilized Nonlinear Lateral Modes of Broad Area Lasers
The lateral modes of broad area lasers are investigated theoretically. The nonlinear interaction between optical field and effective refractive index leads to a saturable nonlinearity in the governing field equation, so that self-modulated solutions are found to be stable with increased current injection above saturation intensity. We derive approximate analytical solutions for traveling wave fields within the broad area laser. The field amplitude consists of a small ripple superimposed on a large dc value. Matching fields at the boundary determines the modulation depth and imparts an overall phase curvature to the traveling wave mode. There are multiple lateral modes for a given set of operating conditions, and modes with successively more lobes in the ripple have greater overall phase curvature. In contrast to the linear problem, several lateral modes can achieve the same modal gain, for a given injected current density, by saturating the gain to different extent. Thus, these modes would exhibit slightly different optical powers
Erratum: The Non-Coding RNA Journal Club: Highlights on Recent Papers-4. Non-Coding RNA 2016, 2, 9.
Please note that in the published editorial [1], affiliations 1, and 8 contained errors.[...]
Laterally coupled-cavity semiconductor lasers
We analyze the threshold behavior of a pair of laterally coupled semiconductor lasers of different lengths. The predictions include longitudinal mode selectivity leading to single longitudinal mode operation with a periodicity determined by the length mismatch, and ripples in the equipower curves in the current plane due to carrier-induced index shifts. We present experimental measurements that confirm these predictions
Differential Changes in Expression of Intestinal Antimicrobial Peptide Genes During Ascaris lumbricoides Infection in Zambian Adults Do Not Respond to Helminth Eradication
Background. Intestinal helminthiasis modulates immune responses to vaccines and environmental allergens. To explore the impact on intestinal host defense, we assessed expression of antimicrobial peptide genes, together with T cell subset markers and cytokines, in patients with ascariasis before and after treatment
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