1,721,086 research outputs found
Polarization-transparent FSR-free microring resonator filter with wide hitless tunability
No full textA coupled microring resonator architecture with non-integer Vernier ratio design and controllable loss is exploited to implement a polarization-transparent hitless tunable FSR-free filter operating over the extended C+L band (1520 nm-1620 nm). (C) 2021 The Author(s
Waveguide design optimization for compact silicon photonic ferroelectric phase shifters
Full text linkIn this paper, a new, to the best of our knowledge, design for a ferroelectric BaTiO3 cladded silicon photonic phase shifter with very small switching length for compact photonic integrated circuits (PICs) is proposed. The proposed design is based on the choice of a waveguide core with suitably slanted sidewalls in order to favor the desired polarization of ferroelectric cladding and to make guided modes spread toward the ferroelectric cladding with the consequence of further reduction in switching length compared to the conventional (rectangular core) structure. The proposed design also gives the additional benefit of having the identical switching length for both TE and TM modes with the same configuration. These results offer a viable strategy to realize compact non-volatile phase shifters for reconfigurable and programmable PICs
Active Compensation of Nonlinear Effects in Silicon Photonic Microring Filters
No full textWe propose a technique for automated active compensation of nonlinear effects in silicon photonic coupled microring resonator filters. Transmission performances of 200 Gbit/s DP 16-QAM signals up to 20 dBm are evaluated
Unscrambling Light Automatically on a Photonic Chip
Full text linkLight beams can get mixed by transmission through a scattering
system like a multimode channel. Separating beams
of the same wavelength and polarization would appear to be
very hard. Although the information carried by the beams is
not fundamentally lost, its recovery requires a coherent interferometric
reconstruction of the original signals, which have
been scrambled among the modes of the system.
In principle, a reconfigurable mesh of 2×2 interferometers
could perform the necessary unitary mathematical operation.1
In practice, however, use of such photonic meshes—the size
of which scales up quadratically with the number of modes—
has been hindered by the need for complex, time-consuming
procedures for calibration, control and configuration. Setting
up and stabilizing a complex network of interferometers can
be challenging, especially for interferometers buried inside
the mesh.
In work this year, we constructed a silicon photonics integrated
mesh that can self-configure automatically to unscramble
arbitrarily mixed optical beams, without any advance knowledge
of the scattering system.2 Our architecture integrates
six thermally controlled Mach-Zehnder interferometers that
are sequentially and automatically adjusted, without calculations,
to simultaneously reconstruct, separate (with a residual
crosstalk of less than –20 dB), and sort out four optical beams
that have been completely mixed in a multimode waveguide.
By keying each signal with a different pilot tone, built-in
transparent detectors3 monitor the evolution of each mode
along the mesh, allowing tuning and adaptive individual feedback
control of each interferometer with a simple, progressive
algorithm.4 The entire mesh, controlled by custom-designed
electronics, resets itself automatically after the mode mixing
is significantly perturbed, can completely reconfigure on a
time scale of a few seconds, and can track modes undergoing
time-varying mixing on a time scale of a few hundred
milliseconds.
Our calibration and control strategy enables scalability to
larger meshes (that is, to higher number of modes) without
substantially increasing control complexity. Further, the principle
of a self-configuring, self-resetting mesh can be extended
to different mesh topologies to implement nonunitary linear
operations4 and emerging programmable photonic processors,5
for applications in fields such as telecommunications, imaging,
sensing, secrecy and quantum information processing. This
work demonstrates that, despite the apparent challenges of
undoing complicated scattering and interferometric mixing
of optical beams, self-configuring and self-stabilizing optics
systems can automatically unscramble light in real time
Spectral Classification and Cloning of Photonic Integrated Filters for Volume Testing
Full text linkVolume testing is rapidly becoming a key step in the production chain of photonic integrated circuits (PICs), which are ever increasing their integration density and complexity, and are penetrating many market sectors. What makes PIC testing peculiar with respect to testing of electronic integrated circuits (EICs) is the fact that it generally requires also control and calibration procedures. Here, we present a method to perform time and cost-efficient volume testing of frequency-selective PICs. The described techniques enable to evaluate the deviation between the spectral responses of a device under test (DUT) and a reference (REF) device, without a direct measurement of the transfer function, which is a time and resource consuming procedure. Information on the DUT status is inferred from the integral power of a top-flat broadband optical source, which is shaped by the REF device and is transmitted through the DUT. In this way it is possible to classify the DUT according to specifically defined metrics, automatically tune it to replicate the REF spectral response and build LookUp Tables (LUTs) to be used in operative conditions. The proposed technique is validated experimentally on a reconfigurable silicon-photonics microring resonator filter implementing a Tuneable Optical Add/Drop Multiplexer, but we also provide conditions for its use for testing of frequency-selective devices
On the Design of Unconventional Optical Phased Array Antennas
No full textThe design of unconventional optical phased array architectures suitable for implementation within photonic integrated circuits, is addressed. Starting from a set of free-space-optics beam pattern requirements, thinned array layouts are optimized using a multi-objective approach with the double goal of minimize the array architecture complexity, while controlling the radiation pattern side lobes and main lobe beam width. A numerical example is reported showing an illustrative design of the proposed method
Automated Cloning and Lookup Table Generation for Reconfigurable Photonic Integrated Filters
No full textWe propose a strategy to automatically replicate the spectral response of photonic filters, here applied to coupled microring resonator architectures. This control scheme is exploited to generate Lookup Tables for devices operating in flexible networks
Canceling Thermal Cross-Talk Effects in Photonic Integrated Circuits
No full textThermal actuators are among the most consolidated and widespread devices for the active control of photonic integrated circuits (PICs). As a main drawback, mutual thermal crosstalk among actuated devices integrated onto the same photonic chip can affect the working point of the PIC and can reduce the efficiency of automated tuning and calibration procedures. In this paper, a strategy to cancel out the effects of the phase coupling induced by thermal crosstalk is presented. In our technique, we named thermal eigenmode decomposition (TED), all the actuators of the PIC are controlled simultaneously according to the eigensolution of the thermally coupled system. The effectiveness of the TED method is validated by numerical simulations and experiments carried out on coupled microring resonator and switch fabrics of Mach-Zehnder interferometers. With respect to individual control of phase actuators, where thermal crosstalk can hinder the convergence of automated tuning algorithms, with the TED technique convergence is always reached, requires a lower number of iterations, and is less sensitive to the initial state of the PIC. The proposed TED method can he applied to generic tuning and locking algorithm, can be employed in arbitrary PIC architectures and its validity can be extended to systems where phase coupling is induced by other physical effects, such as mutual mechanical stress and electromagnetic coupling among RF lines
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