The ability to overcome the negative effects, induced by obstacles and turbulent atmosphere, is a core challenge of long-distance information transmission, and it is of great significance in free-space optical communication. The spatial-coherence structure, that characterizes partially coherent fields, provides a new degree of freedom for carrying information. However, due to the influence of the complex transmission environment, the spatial-coherence structure is severely damaged during the propagation path, which undoubtedly limits its ability to transmit information. Here, we realize the robust far-field orbital angular momentum (OAM) transmission and detection by modulating the spatial-coherence structure of a partially coherent vortex beam with the help of the cross-phase. The cross-phase enables the OAM information, quantified by the topological charge, hidden in the spatial-coherence structure can be stably transmitted to the far field and can resist the influence of obstructions and turbulence within the communication link. This is due to the self-reconstruction property of the spatial-coherence structure embedded with the cross-phase. We demonstrate experimentally that the topological charge information can be recognized well by measuring the spatial-coherence structure in the far field, exhibiting a set of distinct and separated dark rings even under amplitude and phase perturbations. Our findings open a door for robust optical signal transmission through the complex environment and may find application in optical communication through a turbulent atmosphere.

We investigated the Talbot effect in an anti-parity-time (PT) symmetric synthetic photonic lattice composed of two coupled fiber loops. We calculated the band structures and found that with an increase in the gain-loss parameter, the band transitions from a real spectrum to a complex spectrum. We study the influence of phase in the Hermitian operator on the Talbot effect, and the Talbot effect disappears when the period of the input field is N > 8. Further study shows that the variation of Talbot distance can also be modulated by non-Hermitian coefficients of gain and loss. This work may find significant applications in pulse repetition-rate multiplication, temporal invisibility, and tunable intensity amplifiers.

Fractional vortex beams exhibit a higher degree of modulation dimensions than conventional vortices, thus inheriting superior anti-turbulent transmission properties through the incorporation of additional coherence modulation. However, aliasing the mixed modes induced by coherence degradation makes the quantitative measurement of the topological charge in fractional vortex beams challenging. In this study, a coherence phase spectrum was introduced, and experimental demonstrations to quantitatively determine the fractional topological charge of partially coherent fractional vortex beams were performed. By leveraging the four-dimensional measurement of a partially coherent light field, the source coherence function was inversely reconstructed, and fractional topological charges were determined with high precision by extracting the phase spectrum of the coherence function. Laguerre–Gaussian, elliptical Gaussian, and plane-wave-fraction vortex beams with various degrees of coherence were used to demonstrate measurement precision. The proposed method is applicable to X-rays and electron vortices. It has potential applications in optical encryption, high-capacity optical communication, and quantum entanglement.

To improve the processing efficiency and extend the tuning range of 3D isotropic fabrication, we apply the simultaneous spatiotemporal focusing (SSTF) technique to a high-repetition-rate femtosecond (fs) fiber laser system. In the SSTF scheme, we propose a pulse compensation scheme for the fiber laser with a narrow spectral bandwidth by building an extra-cavity pulse stretcher. We further demonstrate truly 3D isotropic microfabrication in photosensitive glass with a tunable resolution ranging from 8 μm to 22 μm using the SSTF of fs laser pulses. Moreover, we systematically investigate the influences of pulse energy, writing speed, processing depth, and spherical aberration on the fabrication resolution. As a proof-of-concept demonstration, the SSTF scheme was further employed for the fs laser-assisted etching of complicated glass microfluidic structures with 3D uniform sizes. The developed technique can be extended to many applications such as advanced photonics, 3D biomimetic printing, micro-electromechanical systems, and lab-on-a-chips.

We introduce the Stokes scintillation indices and the corresponding overall Stokes scintillations for quantitatively studying the fluctuations of both the intensity and polarization of an optical vector beam transmitting through the atmospheric turbulence. With the aid of the multiple-phase-screen method, we examine the Stokes fluctuations of a radially polarized beam in Kolmogorov turbulence numerically. The results show that the overall scintillation for the intensity distribution is always larger than the overall scintillation for the polarization-dependent Stokes parameters, which indicates that the polarization state of a vector beam is stabler than its intensity distribution in the turbulence. We interpret the results with the depolarization effect of the vector beam in turbulence. The findings in this work may be useful in free-space optical communications utilizing vector beams.

Structured light with more extended degrees of freedom (DoFs) and in higher dimensions is increasingly gaining traction and leading to breakthroughs such as super-resolution imaging, larger-capacity communication, and ultraprecise optical trapping or tweezers. More DoFs for manipulating an object can access more maneuvers and radically increase maneuvering precision, which is of significance in biology and related microscopic detection. However, manipulating particles beyond three-dimensional (3D) spatial manipulation by using current all-optical tweezers technology remains difficult. To overcome this limitation, we theoretically and experimentally present six-dimensional (6D) structured optical tweezers based on tailoring structured light emulating rigid-body mechanics. Our method facilitates the evaluation of the methodology of rigid-body mechanics to synthesize six independent DoFs in a structured optical trapping system, akin to six-axis rigid-body manipulation, including surge, sway, heave, roll, pitch, and yaw. In contrast to previous 3D optical tweezers, our 6D structured optical tweezers significantly improved the flexibility of the path design of complex trajectories, thereby laying the foundation for next-generation functional optical manipulation, assembly, and micromechanics.