Prof. Philip Russell (Max Planck Institute for the Science of Light) discusses the development of photonic crystal fibers, in a conversation with Prof. Long Zhang (Chinese Academy of Sciences).

Label-free vibrational stimulated Raman microscopy surpasses the diffraction limit by employing structured illumination, opening new avenues for super-resolution imaging of biological targets.

The study by Shao et al.1 marks a critical advancement in quantum simulations by reporting the first experimental observation of the antiferromagnetic (AFM) phase transition in a 3D fermionic Hubbard model (FHM) using ultracold lithium-6 atoms. This experiment bridges a significant gap in our understanding of strongly correlated systems and provides a new platform to explore low-temperature quantum phases. This commentary will analyze the results, place them in the context of ongoing research, and discuss their broader implications for the field of quantum materials and technologies.

Modern optical communications rely heavily on dense wavelength-division multiplexing (DWDM) technology because of its capability of significantly increasing transmission channels. Here, we demonstrate, for the first time to the best of our knowledge, a compact photonic chip for DWDM transmitters on lithium-niobate-on-insulator (LNOI) by introducing the array of 2×2 Fabry–Perot (FP) cavity electro-optic (EO) modulators. A four-channel LNOI photonic chip for DWDM is designed and realized with a channel spacing of 1.6 nm (which is the narrowest one reported until now for LNOI optical transmitters), exhibiting a total excess loss of 1.3 dB and high 3-dB EO bandwidths of >67 GHz for all channels. Specifically, these four 2×2 FP cavities are designed with broadened LNOI photonic waveguides in the cavity sections, and they are placed very closely on the chip so that their resonance wavelengths are aligned precisely with the desired channel-spacing of ∼1.6 nm. Finally, the generation of 4×80-Gbps on–off keying and 4×100-Gbps PAM4 signals is demonstrated successfully with four channels, and the power consumption is as low as ∼5.1 fJ/bit. The present photonic chip has a compact footprint of about 0.78 mm×0.58 mm, showing great potential to work with more than four channels and to be very useful for future large-capacity optical links.

Recent advances in metasurface lenses (metalenses) have shown great potential for opening a new era in compact imaging, photography, light detection, and ranging (LiDAR) and virtual reality/augmented reality applications. However, the fundamental trade-off between broadband focusing efficiency and operating bandwidth limits the performance of broadband metalenses, resulting in chromatic aberration, angular aberration, and a relatively low efficiency. A deep-learning-based image restoration framework is proposed to overcome these limitations and realize end-to-end metalens imaging, thereby achieving aberration-free full-color imaging for mass-produced metalenses with 10 mm diameter. Neural-network-assisted metalens imaging achieved a high resolution comparable to that of the ground truth image.

Two-photon microscopy provides sectioned excitation, but in practical settings, it often suffers from contrast limitations. Here, we report the observation of a strong acousto-optic modulation of two-photon excited fluorescence. Harnessing this effect yields enhanced image detail and contrast and improves optical sectioning in deep brain tissue in vivo. Ultrasound-modulation assisted multiphoton imaging (UMAMI) is compatible with standard multiphoton microscopes, without requiring changes to the optical path or image acquisition parameters.

Terahertz (THz) communications are vulnerable to eavesdropping due to their scattering and diffraction properties, which limits their practical deployment. We propose a photonic THz chaos encryption and synchronization scheme to secure THz communications. We experimentally demonstrate the generation, encryption, and wireless transmission of a 5 Gbit/s non-return-to-zero signal at 120 GHz using flexible photonic THz chaos. In addition, we achieve high-quality chaos synchronization with a neural network, attaining a correlation coefficient of up to 90.6%. This scheme offers a viable solution for secure THz communications, showing significant potential for enhancing wireless communication privacy.

Soliton molecules, referred to as closely bounded solitons, have recently attracted considerable interest in both fundamental nonlinear physics research and refreshed application promises. To date, extensive efforts have been made on the generation of quadratic soliton molecules. These are soliton molecules whose formation exclusively involves second-order dispersion and Kerr nonlinearity. Here, for the first time, we demonstrate the realization of various third-order dispersion-supported soliton molecules, including vector dark–anti-dark solitons, vector anti-dark solitons, and vector anti-dark soliton molecules formed in a fiber laser with net cavity dispersion near the zero-group-velocity-dispersion point. High-order dispersion could greatly alter the internal soliton interaction within a soliton molecule. This finding could open exciting new avenues in soliton research.