201 research outputs found
Coupling of light from microdisk lasers into plasmonic nano-antennas
An optical dipole nano-antenna can be constructed by placing a
sub-wavelength dielectric (e.g., air) gap between two metallic regions. For
typical applications using light in the infrared region, the gap width is
generally in the range between 50 and 100 nm. Owing to the close
proximity of the electrodes, these antennas can generate very intense
electric fields that can be used to excite nonlinear effects. For example, it is
possible to trigger surface Raman scattering on molecules placed in the
vicinity of the nano-antenna, allowing the fabrication of biological sensors
and imaging systems in the nanometric scale. However, since nano-antennas
are passive devices, they need to receive light from external sources that are
generally much larger than the antennas. In this article, we numerically
study the coupling of light from microdisk lasers into plasmonic nanoantennas.
We show that, by using micro-cavities, we can further enhance the
electric fields inside the nano-antennas
Nonlinear properties of AlGaAs waveguides in continuous wave operation regime
Aluminum Gallium Arsenide (AlGaAs) is an attractive platform for the development of integrated optical circuits for all-optical signal processing thanks to its large nonlinear coefficients in the 1.55-μm telecommunication spectral region. In this paper we discuss the results of the nonlinear continuous-wave optical characterization of AlGaAs waveguides at a wavelength of 1.55 μm. We also report the highest value ever reported in the literature for the real part of the nonlinear coefficient in this material (Re(γ) ≈521 W<sup>−1</sup>m<sup>−1</sup>)
Maximization of Gain in Slow-Light Silicon Raman Amplifiers
We theoretically study the problem of Raman gain maximization in uniform silicon photonic-crystal waveguides supporting slow
optical modes. For the first time, an exact solution to this problem is obtained within the framework of the undepleted-pump
approximation. Specifically, we derive analytical expressions for the maximum signal gain, optimal input pump power, and
optimal length of a silicon Raman amplifier and demonstrate that the ultimate gain is achieved when the pump beam propagates
at its maximum speed. If the signal’s group velocity can be reduced by a factor of 10 compared to its value in a bulk silicon,
it may result in ultrahigh gains exceeding 100 dB. We also optimize the device parameters of a silicon Raman amplifier in the
regime of strong pump depletion and come up with general design guidelines that can be used in practice
Optimized gold nanoshell ensembles for biomedical applications
We theoretically study the properties of the optimal size distribution in the ensemble of hollow gold nanoshells (HGNs) that exhibits the best performance at in vivo biomedical applications. For the first time, to the best of our knowledge, we analyze the dependence of the optimal geometric means of the nanoshells’ thicknesses and core radii on the excitation wavelength and the type of human tissue, while assuming lognormal fit to the size distribution in a real HGN ensemble. Regardless of the tissue type, short-wavelength, near-infrared lasers are found to be the most effective in both absorption- and scattering-based applications. We derive approximate analytical expressions enabling one to readily estimate the parameters of optimal distribution for which an HGN ensemble exhibits the maximum efficiency of absorption or scattering inside a human tissue irradiated by a near-infrared laser
Guided Plasmon Modes of a Graphene-Coated Kerr Slab
We study analytically propagating surface plasmon modes of a Kerr slab sandwiched between two graphene layers. We show that some of the modes that propagate forward at low field intensities start propagating with negative slope of dispersion and positive flux of energy (fast-light surface plasmons) when the field intensity becomes high. We also discover that our structure supports an additional branch of low-intensity fast-light guided modes. The possibility of dynamically switching between the forward and the fast-light plasmon modes by changing the intensity of the excitation light or the chemical potential of the graphene layers opens up wide opportunities for controlling light with light and electrical signals on the nanoscale. © 2015, Springer Science+Business Media New York
Photon Pair Generation in Silicon Micro-Ring Resonator with Reverse Bias Enhancement
Photon sources are fundamental components for any quantum photonic
technology. The ability to generate high count-rate and low-noise correlated
photon pairs via spontaneous parametric down-conversion using bulk crystals has
been the cornerstone of modern quantum optics. However, future practical
quantum technologies will require a scalable integration approach, and
waveguide-based photon sources with high-count rate and low-noise
characteristics will be an essential part of chip-based quantum technologies.
Here, we demonstrate photon pair generation through spontaneous four-wave
mixing in a silicon micro-ring resonator, reporting a maximum
coincidence-to-accidental (CAR) ratio of 602 (+-) 37, and a maximum photon pair
generation rate of 123 MHz (+-) 11 KHz. To overcome free-carrier related
performance degradations we have investigated reverse biased p-i-n structures,
demonstrating an improvement in the pair generation rate by a factor of up to
2, with negligible impact on CAR.Comment: 5 pages, 3 figure
- …