Early Posting

Accepted papers to appear in an upcoming issue

Optica Publishing Group posts prepublication articles as soon as they are accepted and cleared for production. See the FAQ for additional information.

Global Caustic and Phase Chirality Reversal of the Focused Vortex Beam

Chaoxiang Wang, Ping Jiang, Yang Huajun, yan qin, and Liu Jianing

DOI: 10.1364/JOSAA.503536 Received 17 Aug 2023; Accepted 22 Sep 2023; Posted 22 Sep 2023  View: PDF

Abstract: We predict the reversal of the phase chirality before and after the focal plane during propagation based on ray tracing. The interference patterns of a focused vortex beam (FVB) and a plane beam during propagation verify the fact of phase chirality reversal through diffraction theoretical simulations and experiments. Besides, we deduce an analytical expression for the caustic based on the ray equation, which effectively represents the change of the hollow light field during propagation. Simulation and experimental results demonstrate the effectiveness of caustic in describing the variation of the global hollow dark spot radius. Furthermore, based on the caustic results at the focal plane, we customize FVBs with the same dark spot radii but different topological charges. Our research results reveal the characteristics of the light field and phase distribution of the FVB during propagation, which will expand our understanding of the properties of the FVB and provide a reference value for applications such as chiral particle manipulation and topological charge recognition.

Modulation Transfer Function formula for different age ranges

Roberto Sánchez, Francisco Puertas, and Luis Issolio

DOI: 10.1364/JOSAA.494721 Received 17 May 2023; Accepted 19 Sep 2023; Posted 19 Sep 2023  View: PDF

Abstract: The modulation transfer function (MTF) is one of the most complete tools to study the optical performance of the eye. We present the average radial MTF profiles measured in 68 subjects grouped in six age ranges (from 20 to 80 years) and a general formula to estimate the radial profile of human MTF as a function of pupil size and age. The mean MTF for each age group was fitted to an analytical expression to compute two parameters related to aging. The proposed formula fitted reasonably well to experimental data of the bibliography and predicted the average changes with aging of different optical quality parameters obtained from MTF.

UN-PUNet for phase unwrapping from a single uneven and noisy ESPI phase pattern

Hongxuan He, Chen Tang, Liao Zhang, Min Xu, and Zhenkun Lei

DOI: 10.1364/JOSAA.499453 Received 30 Jun 2023; Accepted 19 Sep 2023; Posted 19 Sep 2023  View: PDF

Abstract: The wrapped phase patterns of objects with varying materials exhibit uneven gray values. Phase unwrapping is a tricky problem from a single wrapped phase pattern in ESPI due to the gray unevenness and noise. In this paper, we propose a CNN model named UN-PUNet for phase unwrapping from a single wrapped phase pattern with uneven grayscale and noise. UN-PUNet leverages the benefits of a dual-branch encoder structure, a multi-scale feature fusion structure, a convolutional block attention module, and skip connections. Additionally, we have created an abundant dataset for phase unwrapping with varying degrees of unevenness, fringe density, and noise levels. We also propose a mixed loss function MS_SSIM+L2. Employing the proposed dataset and loss function, we can successfully train the UN-PUNet, ultimately realizing effective and robust phase unwrapping from a single uneven and noisy wrapped phase pattern. We evaluate the performance of our method on both simulated and experimental ESPI wrapped phase patterns, comparing it with DLPU, VUR-Net, and PU-M-Net. The unwrapping performance is assessed quantitatively and qualitatively. Furthermore, we conduct ablation experiments to evaluate the impact of different loss functions and the attention module utilized in our method. The results demonstrate that our proposed method outperforms the compared methods, eliminating the need for pre-processing, post-processing procedures, and parameter finetuning. Moreover, our method effectively solves the phase unwrapping problem while preserving the structure and shape, eliminating speckle noise, and addressing uneven grayscale.

Tunable birefringence and elliptical polarization eigenmodes in a biplate of two quarter-wave plates

Jhon Pabón Niño, Cristian Hernández Cely, and Rafael Torres

DOI: 10.1364/JOSAA.499731 Received 04 Jul 2023; Accepted 12 Sep 2023; Posted 14 Sep 2023  View: PDF

Abstract: The birefringence of elliptical polarization eigenmodes can be conceptualized as a composite system comprising two distinct media: one with linear polarization eigenmodes and the other with circular polarization eigenmodes. However, the practical realization of such a system often involves the combination of two birefringent quarter-wave plates (QWPs). In this study, our objective is to characterize the variable retardation and variable elliptical polarization eigenmodes exhibited by a biplate consisting of two quarter-wave plates. Additionally, we aim to analyze the geometric properties of the transformation of one state of polarization on the Poincaré sphere, employing the emerging states curve. This curve corresponds to the intersection between the Poincaré sphere and a cone. The outcomes of our study are presented as a function of the angle between the fast axes of the two QWPs. The findings have the potential to contribute to the configuration of q-plates and facilitate the development of quantum communication protocols.

Dispersive Perfectly Matched Layers and high order Absorbing Boundary Conditions for electromagnetic quasinormal modes

Guillaume Demesy, Tong Wu, Yoann Brûlé, Frederic Zolla, Andre Nicolet, Philippe Lalanne, and Boris Gralak

DOI: 10.1364/JOSAA.499370 Received 30 Jun 2023; Accepted 01 Sep 2023; Posted 01 Sep 2023  View: PDF

Abstract: Resonances, also known as quasinormal modes (QNM) in the non-Hermitian case, play a ubiquitous role in all domains of physics ruled by wave phenomena, notably in continuum mechanics, acoustics, electrodynamics, and quantum theory. The non-Hermiticity arises from the system losses, whether they are material (Joule losses in electromagnetism) or linked to the openness of the problem (radiation losses). In this paper, we focus on the latter delicate matter when considering bounded computational domains mandatory when using {e.g.} Finite Elements. We address the important question whether dispersive perfectly matched layer and high order absorbing boundary conditions offer advantages in QNM computation and modal expansion of the optical responses compared to non-dispersive PMLs.