We compare the design of three different single mode laser structures consisting in a Reflective Semiconductor Optical Amplifier coupled to a silicon photonic external cavity mirror. The three designs differ for the mirror structure and are compared in terms of SOA power consumption and side mode suppression ratio (SMSR). Assuming then a Quantum Dot active material, we simulate the best laser design using a numerical model that includes the peculiar physical characteristics of the QD gain medium. The simulated QD laser CW characteristics are shown and discussed.
Here we discuss the second harmonic generation (SHG) signal raised by a sample surface manifesting circular dichroism. The measurement were performed by studying the SHG efficiency in different polarization states of the light. In particular measurement performed with circular polarized light showing a very high sensitivity to the response of the studied metasurfaces.
Here we present both an overview of different nonlinear optical phenomena occurring in nanopatterned
materials and new results on the symmetry induced second harmonic generation (SHG) signal from metallic nanowires.
A discussion about symmetry breaking in artificial chiral metamaterials is presented, while the experimental evidence
was given by second order nonlinear optical measurements on different samples.
Here, new SHG measurements on regular array of tilted nanowires (NWs) produced by grazing evaporating
gold on a silicon substrate were presented and discussed.
The surface composed by tilted wires can induce an optical chiral response of the whole sample when the light
impinges on the sample on an out-of-normal incidence angle (extrinsic chirality). The measurements were performed by
using circular polarised laser excitation at the wavelength of 800nm and by observing the second harmonic response at
the wavelength of 400nm in different polarization states.
The second harmonic generation process results to be very sensitive to the symmetry breaking at the interfaces
of investigated samples.
Our main goal is to describe the basic steps for the emission control of the electromagnetic field leaving a tailored slit on a gold film, combined with a plasmonic grating designed on the output face, in order to make the emitted beam acquire the desired irradiation diagram (ID). A suitable numerical tool developed for a fast evaluation of the slit-grating system’s ID allows to spare time in the definition of the selected configurations. The customization of the ID is a primary step for the design of more complex structures with potential useful capabilities for the manipulation of impinging light waves and the consequent rise of interesting electromagnetic patterns.
Here we show the way to easily tune and engineer the optical response of hybrid structures composed by self ordered dielectric nanospheres partially covered by anisotropic plasmonic structures. The overall structure is a hybrid plasmonic-photonics nanostructure acting as a meta-surface witch morphology allows efficient and versatile light manipulation both for linear polarized and circular polarized fields in the visible and near infrared frequencies.
Here we present the measurements of the second harmonic generation (SHG) signal raised by self ordered dielectric nanospheres partially covered by thin (10nm) Au layer. The measurement were performed by studying the SHG efficiency in different polarization states of the light. In particular measurement performed with circular polarized light show the presence of chiral response of the nanospheres that is induced by the particular geometry of the metasurface.
Nonlinear effects can be enhanced and tailored on a subwavelength scale by taking advantage of high field confinement by selective coupling among resonant plasmonic nanostructures, called plasmonic nanoresonators and nanoantennas. In particular, we focus our attention on the process of second-harmonic (SH) generation. Excitation of localized surface plasmon polaritons at the fundamental frequency in these structures can remarkably modify the response of the system by enhancing surface and/or bulk nonlinear contributions to the overall SH field. Moreover, the radiation pattern of the generated field can be controlled and directed. Indeed, the overall structure behaves as a nonlinear nanoantenna for the SH harmonic field, whose emission pattern can be tailored.
We study second harmonic generation from dipole gold nanoantennas by analyzing the different contributions of bulk
and surface nonlinear terms. Numerical calculations have been performed applying a Green's tensor method. The SHG as
a function of the wires cross section size is investigated in both the near and far field regimes. We show that the
excitation of localized surface plasmon polaritons in these structures can remarkably modify the nonlinear response of
the system by enhancing surface and/or bulk contributions, creating regimes where bulk nonlinear terms dominate over
surface linear terms and vice versa. We also report results of calculations performed on Silver coupled 2D-nanoresonators.
Coupling is responsible for the formation of resonant modes that can be localized on small portions of
the structure or distributed over the whole structure.
We have developed a model based on a Green function approach to numerically investigate the second harmonic
generation process in two dimensional metallic nano-objects. The linear optical response of metals in the visible regime
is modeled by taking into account both free and bound electrons contributions. On the other hand, at this stage, only the
contribution of free electrons is considered for the nonlinear response. Both bulk and surface nonlinear polarization
source terms have been evaluated for objects of arbitrary shape. We show that our model has the potential for further
improvements and could be a useful tool to investigate second harmonic emission by single or periodically arranged
metallic sub-wavelength objects in a dielectric host material.
It is shown that by properly using the geometrical optics approximation it is possible to design particular optical
structures able to shape an optical beam in some wanted way. We discuss the application to hide to an incident plane
wave, objects contained in a finite space region.