424 research outputs found
Thermal radiation from optically driven Kerr () photonic cavities
We study thermal radiation from nonlinear () photonic cavities
coupled to external channels and subject to incident monochromatic light. Our
work extends related work on nonlinear mechanical oscillators [Phys. Rev. Lett.
97, 110602 (2006)] to the problem of thermal radiation, demonstrating that
bistability can enhance thermal radiation by orders of magnitude and result in
strong lineshape alternations, including "super-narrow spectral peaks"
occurring at the onset of kinetic phase transitions. We show that when the
cavities are designed so as to have perfect linear absorptivity (rate
matching), such thermally activated transitions can be exploited to
dramatically tune the output power and radiative properties of the cavity,
leading to a kind of Kerr-mediated thermo-optic effect. Finally, we demonstrate
that in certain parameter regimes, the output radiation exhibits Stokes and
anti-Stokes side peaks whose relative magnitudes can be altered by tuning the
internal temperature of the cavity relative to its surroundings, a consequence
of strong correlations and interference between the emitted and reflected
radiation
Real Business Cycle Realizations
Much recent business cycle research focuses on moments of macroeconomic aggregates. We construct examples of real business cycle sample paths for output, consumption, and employment for the U.S. economy. Annual sample paths are generated from an initial condition in 1925, measured technology and government spending shocks since then, and a standard, calibrated, one-sector model of the business cycle. Quarterly sample paths are generated similarly, from an initial condition in 1955. The law of motion for shocks is not parametrized and so decision-rules are estimated by GMM. We compare the paths with actual history graphically and by spectral methods.real business cycles, Solow residuals, US business cycle history
Enhanced nonlinear frequency conversion and Purcell enhancement at exceptional points
We derive analytical formulas quantifying radiative emission from
subwavelength emitters embedded in triply resonant nonlinear
cavities supporting exceptional points (EP) made of dark and leaky modes. We
show that the up-converted radiation rate in such a system can be greatly
enhanced---by up to two orders of magnitude---compared to typical Purcell
factors achievable in non-degenerate cavities, for both monochromatic and
broadband emitters. We provide a proof-of-concept demonstration by studying an
inverse-designed 2D photonic-crystal slab that supports an EP formed out of a
Dirac cone at the emission frequency and a phase-matched, leaky-mode resonance
at the second harmonic frequency
Topology Optimized Multi-layered Meta-optics
We propose a general topology optimization framework for metasurface inverse
design that can automatically discover highly complex multi-layered
meta-structures with increased functionalities. In particular, we present
topology-optimized multi-layered geometries exhibiting angular phase control,
including a single-piece nanophotonic metalens with angular aberration
correction as well as an angle-convergent metalens that focuses light onto the
same focal spot regardless of the angle of incidence
High-efficiency degenerate four wave-mixing in triply resonant nanobeam cavities
We demonstrate high-efficiency, degenerate four-wave mixing in triply
resonant Kerr photonic crystal (PhC) nanobeam cavities. Using a
combination of temporal coupled mode theory and nonlinear finite-difference
time-domain (FDTD) simulations, we study the nonlinear dynamics of resonant
four-wave mixing processes and demonstrate the possibility of observing
high-efficiency limit cycles and steady-state conversion corresponding to
% depletion of the pump light at low powers, even including
effects due to losses, self- and cross-phase modulation, and imperfect
frequency matching. Assuming operation in the telecom range, we predict close
to perfect quantum efficiencies at reasonably low 50 mW input powers in
silicon micrometer-scale cavities
Role of Modern Immunotherapy in Gastrointestinal Malignancies: A Review of Current Clinical Progress
Gastrointestinal (GI) cancers are a group of highly aggressive malignancies with a huge disease burden worldwide. There is clearly a significant unmet need for new drugs and therapies to further improve the treatment outcomes of GI malignancies. Immunotherapy is a novel treatment strategy that is emerging as an effective and promising treatment option against several types of cancers. CTLA-4 and PD-1 are critical immune checkpoint molecules that negatively regulate T cell activation via distinct mechanisms. Immune checkpoint blockade with antibodies directed against these pathways has already shown clinical efficacy that has led to their FDA approval in the treatment of several solid tumors including melanoma, non-small cell lung cancer, renal cell carcinoma, urothelial carcinoma, and head and neck cancer. This review will summarize the current clinical progress of modern immunotherapy in the field of GI tumors, with a special focus on immune checkpoint blockade
Transition from subbarrier to deep subbarrier regimes in heavy-ion fusion reactions
We analyze the recent experimental data of heavy-ion fusion cross sections
available up to deep subbarrier energies in order to discuss the threshold
incident energy for a deep subbarrier fusion hindrance phenomenon. To this end,
we employ a one-dimensional potential model with a Woods-Saxon internuclear
potential. Fitting the experimental data in two different energy regions with
different Woods-Saxon potentials, we define the threshold energy as an
intersect of the two fusion excitation functions. We show that the threshold
energies so extracted are in good agreement with the empirical systematics as
well as with the values of the Krappe-Nix-Sierk (KNS) potential at the touching
point. We also discuss the asymptotic energy shift of fusion cross sections
with respect to the potential model calculations, and show that it decreases
with decreasing energies in the deep subbarrier region although it takes a
constant value at subbarrier energies.Comment: 4 pages, 4 figure
Enhanced Spontaneous Emission at Third-Order Dirac Exceptional Points in Inverse-Designed Photonic Crystals
We formulate and exploit a computational inverse-design method based on topology optimization to demonstrate photonic crystal structures supporting complex spectral degeneracies. In particular, we discover photonic crystals exhibiting third-order Dirac points formed by the accidental degeneracy of monopolar, dipolar, and quadrupolar modes. We show that, under suitable conditions, these modes can coalesce and form a third-order exceptional point, leading to strong modifications in the spontaneous emission (SE) of emitters, related to the local density of states. We find that SE can be enhanced by a factor of 8 in passive structures, with larger enhancements ∼√n³ possible at exceptional points of higher order n.United States. Air Force Office of Scientific Research (FA9550-14-1-0389)National Science Foundation (U.S.) (DMR-1454836)National Science Foundation (U.S.) (DGE1144152
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