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Design of Power-Splitter With Selectable Splitting-Ratio Using Angled and Cascaded MMI-Coupler
A concept of power splitter with selectable splitting-ratios is proposed based on two multimode interference (MMI) sections connected by a phase-shifting region, in which phase-matching conditions can be fulfilled by using a simple angled section or alternatively using matched phase-shifters. The design example of an asymmetrical splitter (10 : 90) is optimized by using the transfer matrix method and three-dimensional full-vectorial beam propagation method. The numerical results reveal that a simple 1.2° angled section can yield a 10 : 90 splitter with an insertion loss of 0.74 dB and a total length of 192 μm. It is also shown that, for the cascaded MMI couplers based splitter, a more compact length of 58 μm with a lower insertion loss of 0.41 dB can be achieved. The fabrication tolerances are also investigated for the proposed asymmetrical power splitter
Integrated photonic quantum gates for polarization qubits
Integrated photonic circuits have a strong potential to perform quantum
information processing. Indeed, the ability to manipulate quantum states of
light by integrated devices may open new perspectives both for fundamental
tests of quantum mechanics and for novel technological applications. However,
the technology for handling polarization encoded qubits, the most commonly
adopted approach, is still missing in quantum optical circuits. Here we
demonstrate the first integrated photonic Controlled-NOT (CNOT) gate for
polarization encoded qubits. This result has been enabled by the integration,
based on femtosecond laser waveguide writing, of partially polarizing beam
splitters on a glass chip. We characterize the logical truth table of the
quantum gate demonstrating its high fidelity to the expected one. In addition,
we show the ability of this gate to transform separable states into entangled
ones and vice versa. Finally, the full accessibility of our device is exploited
to carry out a complete characterization of the CNOT gate through a quantum
process tomography.Comment: 6 pages, 4 figure
Integrated Photonic Sensing
Loss is a critical roadblock to achieving photonic quantum-enhanced
technologies. We explore a modular platform for implementing integrated
photonics experiments and consider the effects of loss at different stages of
these experiments, including state preparation, manipulation and measurement.
We frame our discussion mainly in the context of quantum sensing and focus
particularly on the use of loss-tolerant Holland-Burnett states for optical
phase estimation. In particular, we discuss spontaneous four-wave mixing in
standard birefringent fibre as a source of pure, heralded single photons and
present methods of optimising such sources. We also outline a route to
programmable circuits which allow the control of photonic interactions even in
the presence of fabrication imperfections and describe a ratiometric
characterisation method for beam splitters which allows the characterisation of
complex circuits without the need for full process tomography. Finally, we
present a framework for performing state tomography on heralded states using
lossy measurement devices. This is motivated by a calculation of the effects of
fabrication imperfections on precision measurement using Holland-Burnett
states.Comment: 19 pages, 7 figure
MULTI-MODE AND SINGLE MODE POLYMER WAVEGUIDES AND STRUCTURES FOR SHORT-HAUL OPTICAL INTERCONNECTS
Single mode and multi-mode polymer optical waveguides are a viable solution for replacing copper interconnects as high speed and large bandwidth short-haul optical interconnects in next-generation supercomputers and data servers. A precision laser direct writing method is implemented for producing various single mode and multi-mode polymer waveguide structures and their performance is evaluated experimentally showing agreement with theoretically developed models. The laser direct writing method is the optimal solution for low-rate cost-effective prototyping and large area panel production.
A single mode polymer waveguide bridge module for silicon to glass optical fibers is designed, modeled, fabricated, and measured. The bridge module is designed for waveguide pitch control and low coupling loss from high-density silicon photonic interconnects within CMOS devices and optical silica fibers for long-haul low-loss transmission. A fan-out structure using waveguide S-bend structures is utilized to perform pitch control. Optical coupling within the bridge module is achieved through a novel polymer taper structure to reduce the numerical aperture mismatch between silicon waveguides and silica fibers. Research and development has been implemented into the theoretical understanding and experimental assessments of solving practical interconnect challenges for commercial realization of polymer waveguides
Single-mode and single-polarization photonics with anchored-membrane waveguides
An integrated photonic platform with anchored-membrane structures, the
T-Guide, is proposed and numerically investigated. These compact air-clad
structures have high index contrast and are much more stable than prior
membrane-type structures. Their semi-infinite geometry enables single-mode and
single-polarization (SMSP) operation over unprecedented bandwidths. Modal
simulations quantify this behavior, showing that an SMSP window of 2.75 octaves
(1.2 - 8.1 {\mu}m) is feasible for silicon T-Guides, spanning almost the entire
transparency range of silicon. Dispersion engineering for T-Guides yields broad
regions of anomalous group velocity dispersion, rendering them a promising
platform for nonlinear applications, such as wideband frequency conversion
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