INTEGRATED PHOTONIC DEVICES AND COMPONENTS FOR LINEAR, NONLINEAR AND QUANTUM OPTICAL APPLICATIONS
DISPOSITIFS ET COMPOSANTS PHOTONIQUES INTÉGRÉS POUR DES APPLICATIONS OPTIQUES LINÉAIRES, NON LINÉAIRES ET QUANTIQUES
Résumé
Photonic technologies hold the potential to replace electronic technologies in near future
by solving most of the drawbacks of the electronic circuits. Generation and
manipulation of photons in an integrated waveguide-based platform are preferred
over bulk-optical components, mainly due to their compactness, stability, scalability,
connectivity, reproducibility, and low power consumptions. Sophisticated fabrication
techniques have enabled to design low-loss intricate planar and non-planar
architectures consisting of several twists and turns. Optical directional couplers
(DCs), polarization beam splitters (PBSs), microring resonators (MRRs), etc. are
some of the indispensable components of the photonic circuits having a plethora
of applications in the linear, nonlinear, and quantum optical applications. Silicon
(Si) has been the preferred material to design the photonic components due to the
high refractive-index, low-loss, low-cost, and high nonlinearity.
A corpus of works has been done to shrink the overall device footprint during
the last few decades. At the beginning of the dissertation, a novel scheme to
miniaturize the existing designs of optical DCs and PBSs based on off-centered,
asymmetric, and hybrid dielectric slot waveguides is discussed. Slot dimensions
and positions are optimized to achieve maximum coupling coefficient (> 88% enhancement)
between two adjacent silicon wire-waveguides. The scheme leads to
the device-length of 0.9 um, and 1.1 um, for the DC and the PBS, respectively,
which is a significant improvement over their contemporary counterparts. To
obtain ripple-free broadband band-pass or band-rejection filters, serially coupled
MRRs have been utilized which occupy large space on a chip. To overcome this
issue, non-concentric (off-axis) nested MRR has been proposed in this thesis work
that reduces the filter-size without compromising its performance, thereby enabling
high-density photonic integration on-chip. High thermo-optic coefficient of
Si is the Achilles heel of the silicon-on-insulator MRR based electro-optic modulators
(EOMs). Off-axis MRR also helps to mitigate the thermal red-shift in the spectral response of an MRR which facilitates its applicability to achieve athermal
EOM. By further improvement in non-concentric nested MRRs, it is possible to attain
and maintain high quality-factor and high extinction-ratio with a fabrication
tolerance of 10-20%. Initial experiments on nested MRRs confirm the theoretical
predictions. Such nested congurations will be highly efficient in bio-sensing and
quantum applications for a broad ambient temperature range.
The Kerr nonlinearity of the microresonators has been exploited through a
narrow line-width continuous-wave laser source for the generation of equispaced
coherent frequency lines known as the optical frequency comb (FC). Most of the
nonlinear materials used to generate FC, including Si, exhibit nonlinear losses
and free-carrier effects in the telecom wavelength range. In the next part of the
thesis, an analytical model of FC in the presence of nonlinear losses, free-carrier
absorption, and dispersion effects has been developed, which capacitates us to
explain several experimental results previously obtained. Further, numerical simulations
explore that, using dual-pump, it is possible to generate tunable FC
and synchronous all-optical buffers, which are robust to the writing-jitters, 3rd order
dispersion, and Raman effect. Apart from linear and nonlinear applications,
integrated optical devices provide an efficient testbed for the realization of the
invincible quantum technologies. In the final portion of the dissertation, efficient
pumping schemes have been discussed to generate continuous variable bipartite
and multipartite entanglement in different waveguide-pairs, simultaneously, using
an integrated 5X5 periodically poled lithium niobate waveguide array through
spontaneous parametric down conversion.
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Final PhD Thesis Raktim Haldar 14EC91R07 IITKGP Nov 2019.pdf (131.21 Mo)
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