查看更多>>摘要：? 2021 Elsevier B.V.We present a scheme to realize multiple-qubit quantum state transfer and quantum logic gate by combining the advantages of Vitanov-style pulses and dressed-state-based shortcut to adiabaticity (STA) in Rydberg atoms. The robustness of the scheme to spontaneous emission can be achieved by reducing the population of Rydberg excited states through STA technology. Meanwhile, the control errors can be minimized through using the well-designed pulses. Moreover, the dressed-state method applied in the scheme makes the quantum state transfer more smoothly turned on or off with high fidelity and also faster than traditional shortcut to adiabaticity methods. By using Rydberg antiblockade (RAB) effect (Su et al., 2020 [1]), the multiple-qubit Toffoli gate can be constructed under a general selection conditions of the parameters.
查看更多>>摘要：? 2021 Elsevier B.V.In this paper, we demonstrate the shaping of an incident Gaussian beam into a tunable hyperbolic Airy-like beam, using an acoustooptics cell. The latter contains a transparent liquid (water), where an ultrasound wave propagating and creating a sinusoidal refractive index variation (giving rise to a sinusoidal phase transmittance). By adding an aperture, this sinusoidal phase transmittance becomes equivalent to a cubic phase (sin(x)≈x?x3/3! for x<0.2λa, λa is the ultrasound wavelength), which allows the generation of a tunable Airy-like beam. Using the Fresnel-Kirchhoff diffraction integral, we derive analytical expressions for the diffracted Gaussian beam by the acoustooptics cell in two cases; (a) with and (b) without the aperture. For the first case, the algebra is straightforward and the field has a closed analytical expression, however for the second case, the diffraction integral has no analytical expression, thus, we expand the aperture into a weighted sum of Gaussian functions, to overcome such problem. Based on the obtained mathematical expressions, we study the effect of each parameter of the acoustooptics interaction, on the propagation behavior of the generated Airy-like beam. We believe that the results of this paper could be useful for many interesting applications, involving Airy beams, such as particle manipulation, optical tweezing, and optical communication.
查看更多>>摘要：? 2021 Elsevier B.V.A novel microstructured polymer tube (MPT) incorporating a central hollow, ring core, porous outer cladding is proposed for terahertz (THz) orbital angular momentum (OAM) guidance, focusing on the enhancement of the quantity of modes and bandwidth. The proposed MPT can support 70 modes (66 THz OAM ones) with large mode effective refractive index separation (>2.197×10?3) over 0.6～1.25 THz while maintaining single-mode condition radially, and the number of guiding modes can be further increased by properly equiproportional enhancing the size of the tube. Besides, the designed MPT has strong confinement property, high purity (>97.06%), and flat dispersion over the whole operating bandwidth. The result of this work reveals that this kind of MPT is promising to accelerate the development of the compact, light-weight THz communication system, and can be applied in OAM-based mode-division multiplexing combined with wavelength-division multiplexing technique without multiple-input multiple-output digital signal processing.
查看更多>>摘要：? 2021The microwave light emitting plasma (MLEP) is an important environmentally friendly UV light source. Finding the optimal condition (pressure, ratio and microwave power) of a MLEP spectral line which makes its intensity strongest is the key work to improve its efficiency in applications, but it has not been studied under the condition with multiple variables yet. In this paper, taking Ar+N2 MLEP as an example, a novel method for optimizing the condition of MLEP by employing ANN to model the relationship between the condition and target spectral line intensity using experimental optical emission spectra data is proposed for the first time. The evaluation parameters showed that the ANN has good prediction accuracy. The optimal pressure, Ar concentration and microwave power were simultaneously predicted for UV spectral lines of 281.13 nm, 295.27 nm, 308.91 nm, 313.14 nm, 336.14 nm and 353.00 nm of Ar+N2 MLEP. Their intensities were increased by 53%, 22%, 64%, 17%, 20% and 22% respectively under the predicted optimal condition compared with the maximum intensity in pure experimental method. Therefore, the proposed method is feasible for optimizing the condition of UV luminescence of MLEP, and has great significance in accurately improving the specific spectral line intensity of light sources.
查看更多>>摘要：? 2021 Elsevier B.V.Through taking maximum advantage of fast data processing characteristic of optical computing, optronic convolutional neural networks (OPCNNs) make all computation operations executed in optics to reduce calculation burden in electronic to the maximum extent and successfully performing classification tasks on both hand-written digit dataset and fashion product dataset. However, practical performance of OPCNNs is sensitive to the position variation of testing images caused by whether the alignment error of components or the translation of classified target. The classification performance reduction in such situations severely limits the application scenarios of OPCNNs. In this paper, we improve the original architecture and achieve position-robust optronic convolutional neural networks (PROPCNNs) with translation invariance through replacing strided convolutional operation and fully connected operation with spectral pooling and global average pooling. PROPCNNs contain less optical components and experiments demonstrate their streamlined architecture is capable of maintaining prediction performance in majority situation of images position variation. This consistent performance provides support for applying our architecture in more complex environment such as loaded on moving vehicles or transported in portable way.
查看更多>>摘要：? 2021 Elsevier B.V.In this paper, we proposed an effective method to generate tunable sub-wavelength longitudinal polarized optical needle arrays. Based on the vector diffraction theory, a radially polarized light beam is tailored with a self-designed binary-phase filter (BPF), which is engineered on demand by particle swarm optimization (PSO) algorithm. We are able to garner single longitudinally polarized sub-wavelength (0.433λ) and long (6λ) optical needle with almost perfect uniformity of 98%, ultrahigh beam quality of 96%, and negligible sidelobe of 15%. Furthermore, we engineer a novel multi-focus phase filter (MFPF) in combination with the initial binary filter. It is found that longitudinally polarized sub-wavelength optical needle arrays (ONAs) can be created in the focal volume. More impressively, in addition to maintaining all of properties of single light needle, the number, position, and texture of the optical needles could be mediated flexibly through the MFPF, thus leading to tunable optical needle array. The findings demonstrated here may evoke wide-ranging applications in material processing, lithography and fluorescence imaging.
查看更多>>摘要：? 2021 Elsevier B.V.System geometrical calibration is critical for accurate stereo deflectometry. Conventional calibration approaches involve displaying checkerboard, circle, or fringe patterns on a systemic LCD screen, and the system parameters are calculated via reflection using a markerless mirror at three different locations. These approaches introduce form errors into the system because of defocus images. When using fringe patterns, the calibration procedure becomes more complex for acquiring a plethora of fringe patterns in two orthogonal directions, and ambient light influences the accuracy of the unwrapped phase map. In this study, we propose a novel calibration method for a stereo deflectometry system using a speckle pattern to improve the system measurement accuracy with a flexible calibration procedure. The proposed method includes an improved similarity evaluation function based on KAZE features to improve the accuracy of feature matching between images with perspective transformation, and a coarse-to-precise algorithm is applied to suppress the defocusing effect and refine the matched set. The initial geometrical parameters are calculated based on the refined matching results. The final procedure optimises all geometrical parameters into a single cost function using the Levenberg–Marquardt algorithm. Experiments using a stereo deflectometry system demonstrated that the proposed method achieves high accuracy with while being simple and flexible.
查看更多>>摘要：? 2021 Elsevier B.V.Non-diffracting beams have contributed greatly to recent developments in high power applications such as laser micromachining. Well known for their elongated focal region (also known as a focal line) are zeroth-order Bessel and Bessel vortical beams which allow achieving high aspect ratio modifications inside transparent materials. A superposition of several optical Bessel vortices of different topological charges allows generating high aspect ratio beams with complexly engineered transverse intensity patterns. Non-diffracting Bessel vortices commonly are created using a conical prism — an axicon. Therefore, they can be referred to as axicon beams. In this work, we have studied the formation of high power and energy axicon vortical beams both numerically and experimentally. We have inscribed sub-wavelength birefringent structures inside fused silica glass to create geometrical phase elements for the azimuthal modulation of the spatial spectra of a zeroth-order axicon (Bessel) beam which allows creating a high power superposition of several Bessel vortices. To prove the concept, we apply azimuthally modulated axicon vortical beams to create modifications inside fused silica glass samples.
查看更多>>摘要：? 2021 Elsevier B.V.The display quality of lens-based integral imaging systems can be negatively affected by lens aberrations. However, different regions of an elemental image (EI) are covered by different fields of a lens, leading to variation in the aberrations within a single EI. And the pre-correction of aberrations using a Wiener filter can produce ringing artifacts in regions with severe aberrations, while the use of a convolutional neural network (CNN) for pre-correction can produce an image that is more blurry than with a Wiener filter in areas with slight aberrations. Therefore, a combined pre-correction method is proposed in the present study based on the variation in aberration severity, with each EI is divided into regions with slight aberrations and regions with severe aberrations. The former is pre-corrected using a Wiener filter, and the latter is pre-corrected using a CNN. The regions are then stitched together to produce a joint corrected EI for final optical reconstruction. We validate our approach using simulated and experimental data and compare the results to Wiener filtering and CNN learning individually.
查看更多>>摘要：? 2021 The Author(s)We demonstrate analytically and numerically that the transverse spatial coherence (the spectral degree of coherence) of the field radiated by two partially correlated electromagnetic sources oscillates as a function of propagation distance in free space. In particular, it is possible for its magnitude to completely collapse to zero on propagation, and then return again to unity at a further distance. Our results are a direct demonstration of the wave character of the optical correlation functions. A similar oscillatory effect occurs for the degree of polarization.
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