93 research outputs found
Tailoring Optical Complex Fields with Nano-Metallic Surfaces
Recently there is an increasing interest in complex optical fields with spatially inhomogeneous state of polarizations and optical singularities. Novel effects and phenomena have been predicted and observed for light beams with these unconventional states. Nanostructured metallic thin film offers unique opportunities to generate, manipulate and detect these novel fields. Strong interactions between nano-metallic surfaces and complex optical fields enable the development of highly compact and versatile functional devices and systems. In this review, we first briefly summarize the recent developments in complex optical fields. Various nano-metallic surface designs that can produce and manipulate complex optical fields with tailored characteristics in the optical far field will be presented. Nano-metallic surfaces are also proven to be very effective for receiving and detection of complex optical fields in the near field. Advances made in this nascent field may enable the design of novel photonic devices and systems for a variety of applications such as quantum optical information processing and integrated photonic circuits
Optimization-Free Optical Focal Field Engineering through Reversing the Radiation Pattern from a Uniform Line Source
A simple and flexible method is presented for the generation of optical focal field with prescribed characteristics. By reversing the field pattern radiated from a uniform line source, for which the electric current is constant along its extent, situated at the focus of a 4Pi focusing system formed by two confocal high-NA objective lenses, the required illumination distribution at the pupil plane for creating optical focal field with desired properties can be obtained. Numerical example shows that an arbitrary length optical needle with extremely high longitudinal polarization purity and consistent transverse size of ~0.36λ over the entire depth of focus (DOF) can be created with this method. Coaxially double-focus with spot size of ~0.36λ in the transversal direction and ~λ in the axial direction separated by a prescribed spacing is illustrated as another example. The length of optical needle field and the interval between double-focus are determined by the length of uniform line source. These engineered focal fields may found potential applications in particle acceleration, optical microscopy, optical trapping and manipulations
Creation of Identical Multiple Focal Spots with Prescribed Axial Distribution
We present a scheme for the construction of coaxially equidistant multiple focal spots with identical intensity profiles for each individual focus and a predetermined number and spacing. To achieve this, the radiation field from an antenna is reversed and then gathered by high numerical aperture objective lenses. Radiation patterns from three types of line sources, i.e., the electric current, magnetic current and electromagnetic current distributions, with cosine-squared taper are respectively employed to generate predominately longitudinally polarized bright spots, azimuthally polarized doughnuts, and focal spots with a perfect spherically symmetric intensity distribution. The required illuminations at the pupil plane of a 4Pi focusing configuration for the creation of these identical multiple focal spots can be easily derived by solving the inverse problem of the antenna radiation field. These unique focal field distributions may find potential applications in laser direct writing and optical microscopy, as well as multiple-particle trapping, alignment, and acceleration along the optical axis
Tailoring Optical Complex Field with Spiral Blade Plasmonic Vortex Lens
Optical complex fields have attracted increasing interests because of the novel effects and phenomena arising from the spatially inhomogeneous state of polarizations and optical singularities of the light beam. In this work, we propose a spiral blade plasmonic vortex lens (SBPVL) that offers unique opportunities to manipulate these novel fields. The strong interaction between the SBPVL and the optical complex fields enable the synthesis of highly tunable plasmonic vortex. Through theoretical derivations and numerical simulations we demonstrated that the characteristics of the plasmonic vortex are determined by the angular momentum (AM) of the light, and the geometrical topological charge of the SBPVL, which is govern by the nonlinear superposition of the pitch and the number of blade element. In addition, it is also shown that by adjusting the geometric parameters, SBPVL can be utilized to focus and manipulate optical complex field with fractional AM. This miniature plasmonic device may find potential applications in optical trapping, optical data storage and many other related fields
Workflow-based Fast Data-driven Predictive Control with Disturbance Observer in Cloud-edge Collaborative Architecture
Data-driven predictive control (DPC) has been studied and used in various
scenarios, since it could generate the predicted control sequence only relying
on the historical input and output data. Recently, based on cloud computing,
data-driven predictive cloud control system (DPCCS) has been proposed with the
advantage of sufficient computational resources. However, the existing
computation mode of DPCCS is centralized. This computation mode could not
utilize fully the computing power of cloud computing, of which the structure is
distributed. Thus, the computation delay could not been reduced and still
affects the control quality. In this paper, a novel cloud-edge collaborative
containerised workflow-based DPC system with disturbance observer (DOB) is
proposed, to improve the computation efficiency and guarantee the control
accuracy. First, a construction method for the DPC workflow is designed, to
match the distributed processing environment of cloud computing. But the
non-computation overheads of the workflow tasks are relatively high. Therefore,
a cloud-edge collaborative control scheme with DOB is designed. The low-weight
data could be truncated to reduce the non-computation overheads. Meanwhile, we
design an edge DOB to estimate and compensate the uncertainty in cloud workflow
processing, and obtain the composite control variable. The UUB stability of the
DOB is also proved. Third, to execute the workflow-based DPC controller and
evaluate the proposed cloud-edge collaborative control scheme with DOB in the
real cloud environment, we design and implement a practical workflow-based
cloud control experimental system based on container technology. Finally, a
series of evaluations show that, the computation times are decreased by 45.19%
and 74.35% for two real-time control examples, respectively, and by at most
85.10% for a high-dimension control example.Comment: 58 pages and 23 figure
Genuine full characterization of partially coherence beam
For partially coherent light fields with random fluctuations, the intensity
distributions and statistics have been proven to be more propagation robust
compared with coherent light. However, its full potential in practical
applications has not been realized due to the lack of four-dimensional optical
field measurement. Here, a general modal decomposition method of partially
coherent light field is proposed and demonstrated. The decomposed random modes
can be used to, but not limited to, reconstruct average intensity, cross
spectral density and orthogonal decomposition properties of the partially
coherent light fields. Due to its versatility and flexibility, this method
provides a powerful tool to further reveal light field invariant or retrieve
embedded information after propagation through complex media. The
Gaussian-shell-model beam and partially coherent Gaussian array are used as
examples to demonstrate the reconstruction and even prediction of second-order
statistical characteristics. This method is expected to pave the way for
applications of partially coherent light in optical imaging, optical encryption
and anti-turblence optical communication
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