The family of III-V semiconductors is of high significance in photonics for
two main reasons. First, not only they are the most practical material platforms for active photonic devices but also they are suitable for monolithic
integration of passive and active photonic devices. Second, some III-V compounds exhibit high values of second and third-order nonlinear coefficients
– the property useful in all-optical signal processing and wavelength conversion. This Ph.D. thesis explores the above perspectives with two candidates
from the group III-V family, namely AlGaAs and InGaAsP. The dissertation
consists of two main parts. The first part is dedicated to the theoretical modelling of nonlinear bianisotropic AlGaAs metasurfaces, while the second part
focuses on the experimental studies of the nonlinear optical performance of
InGaAsP waveguides.
Concerning the first part, due to the high confinement of light supported by
the Mie resonances, AlGaAs nanoantennas and metasurfaces with both high
refractive index and high nonlinear susceptibility have found a unique place
in planar nonlinear optics, where not only the presence of high intensity of
light is of significant matter, but also the optically thin thickness of the entities releases the device from phase matching. We first describe the linear optical properties of AlGaAs meta-atoms and metasurfaces such as relatively
high scattering cross-sections and the bianisotropic effect. Also, we derive
and explain all required analytic formulas for this purpose. Bianisotropic
metasurfaces with magnetoelectric coupling and asymmetric optical properties have sparked considerable interest in linear meta-optics. However, further in this thesis, we explore the nonlinear features of bianisotropic AlGaAs
metasurfaces. In particular, we explore a second-harmonic generation in a
bianisotropic AlGaAs metasurface based on the multipolar interference inside the meta-atoms and the nonlinear polarization current. We theoretically
demonstrate that it is possible to obtain several orders of magnitude secondharmonic power differences for the forward and backward illuminations by
adjusting the geometrical parameters of the meta-atoms in such a way that quasi-bound states in the continuum (quasi-BICs) are achievable. This research paves the way for the generation of directional higher-order waves.
Concerning the second part, the research is focused on exploring nonlinear
material platforms for monolithic integration of active and passive devices
on the same chip. In this regard, we explore InGaAsP/InP waveguides of
different geometries. First, we provide the theoretical background such as
the nonlinear Schrodinger equation and four-wave mixing (FWM) equations
in a nonlinear waveguide, then we solve the set of FWM equations using
MATLAB to observe the qualitative behavior of the signal, idler, and the
pump inside a nonlinear waveguide. Furthermore, we design and employ
two waveguide geometries i.e. half-core and nanowire waveguides. We first
design these waveguides so that achieving zero group velocity dispersion
is possible through a suitable material composition and certain geometrical dimensions. However, for the rest of the work, we continued with the
waveguides of different dimensions compared to the designed ones (due
to some limitations in fabrication). We demonstrate self-phase modulation
(SPM) and FWM for the half-core waveguides. For the case of the nanowire
waveguides, we also demonstrate the FWM effect. We measured and extracted the effective value of the nonlinear refractive index of InGaAsP/InP
waveguides to be n2 = 1.9 × 10−13 cm2/W through the relation between the
idler and the pump power when the phase mismatch is negligible. Finally,
we experimentally observe the two-photon absorption effect in our waveguides through the nonlinear characteristics of input and output powers of the
waveguides from which the two-photon absorption coefficient of 19 cm/GW
is calculated.
| Identifer | oai:union.ndltd.org:uottawa.ca/oai:ruor.uottawa.ca:10393/44135 |
| Date | 04 October 2022 |
| Creators | Mobini, Ehsan |
| Contributors | Dolgaleva, Ksenia |
| Publisher | Université d'Ottawa / University of Ottawa |
| Source Sets | Université d’Ottawa |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | application/pdf |
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