Three-dimensional (3D) glass chips are promising waveguide platforms for building hybrid 3D photonic circuits due to their 3D topological capabilities, large transparent windows, and low coupling dispersion. At present, the key challenge in scaling down a benchtop optical system to a glass chip is the lack of precise methods for controlling the mode field and optical coupling of 3D waveguide circuits. Here, we propose an overlap-controlled multi-scan (OCMS) method based on laser-direct lithography that allows customizing the refractive index profile of 3D waveguides with high spatial precision in a variety of glasses. On the basis of this method, we achieve variable mode-field distribution, robust and broadband coupling, and thereby demonstrate dispersionless LP₂₁-mode conversion of supercontinuum pulses with the largest deviation of <0.1 dB in coupling ratios on 210 nm broadband. This approach provides a route to achieve ultra-broadband and low-dispersion coupling in 3D photonic circuits, with overwhelming advantages over conventional planar waveguide-optic platforms for on-chip transmission and manipulation of ultrashort laser pulses and broadband supercontinuum.

One of the major challenges in the rapidly advancing field of nanophotonics is creating high-aspect-ratio nanostructures over large-area with consistent precision. Traditional techniques like photolithography and etching fall short, being limited to fabricating structures with a typical feature size of 100 nm and a maximum aspect ratio of 30:1. To break through these barriers, herein we introduce a strategy, called wet-chemical etching assisted aberration-enhanced single-pulsed femtosecond laser-supplemented nanolithography (WEALTH), for manufacturing large-area deep holey nanostructures. This strategy enables fabrication of nanostructures with diameters as small as 25 nm (exceeding 1/30 of Abbe’s diffraction limit), aspect ratios greater than 10⁴:1, and large-area holey lattices spanning 10 mm² with potential scalability up to several cm². We have successfully harnessed this technique to develop cutting-edge applications, including immunoassay biosensing chips, large-area nanophotonic crystals, nanophotonic crystal microcavities, and chiral nanophotonic devices. Moreover, it is adaptable to a wide range of materials, including crystals, glasses, and silicon-based semiconductors. Our approach offers high flexibility in customizing large-area holey nanophotonic structures, paving the way for breakthrough advancements in 3D integrated optics.

Laser‐induced periodic surface structure (LIPSS) can form structural color on the metal surfaces with high production efficiency and thermal stability, and has been used in various industrial applications such as unfaded color marking and anti‐counterfeiting. Herein, a novel fabrication scheme of multilayer LIPSS is proposed by multiple writing in situ with changing the laser polarization direction, to exhibit an effect of color superposition. To verify this approach, the color formation mechanism of LIPSS on the stainless‐steel surface is analyzed by finite‐element numerical calculation and reveals that the high‐angular dispersion of LIPSS is mainly the result of optical diffraction occurring on the surface of periodic structures. The relationship between the angular dispersion of multilayer LIPSS and laser‐processing parameters is established. Through the proposed multilayer LIPSS coloring technology, vivid full‐color patterns on the steel surface are demonstrated, and the in situ superposition of three‐layer graphs is realized, which can greatly enrich the color levels and be competitive in industrial applications.

High-gain materials and high-quality structures are the two main conditions that determine the amplification performance of optical waveguides. However, it has been hard to balance each other, to date. In this work, we demonstrate breakthroughs in both glass optical gain and optical waveguide structures. We propose a secondary melting dehydration technique that prepares high-quality Er³⁺–Yb³⁺ co-doped phosphate glass with low absorption loss. Additionally, we propose a femtosecond laser direct-writing technique that allows controlling the cross section, size, and mode field of waveguides written in glass with high accuracy, leveraging submicron-resolution multi-scan direct-writing optical waveguide technology, which is beneficial for reducing insertion loss. As a proof of concept demonstration, we designed and fabricated two kinds of waveguides, namely, LP₀₁- and LP₁₁-mode waveguides in the Er³⁺–Yb³⁺ co-doped phosphate glass, enabling insertion loss as low as 0.9 dB for a waveguide length of 2 mm. Remarkably, we successfully achieved an optical amplification for both the waveguides with a net gain of >7 dB and a net-gain coefficient of >3.5 dB/mm, which is approximately one order of magnitude larger than that in the Er³⁺–Yb³⁺ co-doped phosphate glass fabricated by the traditional melt-quenching method. This will open new avenues toward the development of integrated photonic chips.