We experimentally demonstrate ultrafast laser-writing wide-gamut structural colors on TiAlN thin film that is coated on TiN substrate via laser-induced surface oxidation. The experiments involve thorough control over laser parameters, including powers, scanning speeds and pulse durations, to investigate the interplay between these variables and the resulting structural colors. Surface characterization techniques, such as scanning electron microscopy, energy-dispersive x-ray spectroscopy and atomic force microscopy, are employed to analyze the properties of laser-induced oxide layers and their chromatic responses. Our findings indicate that while laser powers and scanning speeds are critical in determining the irradiated dose and the subsequent coloring effects, the pulse duration exerts a distinct influence, particularly at low laser powers as well as slow scanning speeds. Longer pulse durations are found to produce a more significant coloring change despite exhibiting lower oxygen content. This is attributed to the increased surface roughness and deeper oxidation layer achieved with prolonged pulses. We propose two oxidation mechanisms – photo-oxidation and thermal-oxidation – to elucidate the influence of pulse duration on laser coloring effects. These findings not only refine existing paradigms in laser-induced surface coloration but also stimulate further exploration of structural colors’ multifaceted applications across diverse technological contexts.

In this study, a ray tracing model based on the law of reflection in vector form was developed to obtain the design parameters of multipass cells (MPC) with dense spot patterns. Four MPCs with distinct patterns were obtained using an established mathematical model. An MPC with a four-concentric-circle pattern exhibited the longest optical path length (OPL) of approximately 38 m and an optimal ratio of optical path length to volume (RLV) of 13.8 cm^-2. A light-induced thermoelastic spectroscopy (LITES)-based methane (CH₄) sensor was constructed for the first time using the developed optimal MPC and Raman fiber amplifier (RFA). A novel trapezoidal-tip quartz tuning fork (QTF) was used as the detector to further improve the sensing performance. The CH₄-LITES sensor exhibited an excellent linear response to optical power and CH₄ concentration. The minimum detection limit (MDL) of the CH₄-LITES sensor reached 322 ppb when the output optical power of the RFA was 350 mW. The Allan deviation of the system indicated that the MDL decreased to 59.5 ppb when the average time was increased to 100 s.

Femtosecond laser fabrication technology has been applied to photonic-lantern mode (de)multiplexers owing to its 3D fabrication capability. Current photonic-lantern mode (de)multiplexer designs based on femtosecond laser fabrication technology mostly follow a fibre-type photonic lantern design, which uses trajectory-symmetry structures with non-uniform waveguides for selective mode excitation. However, non-uniform waveguides can lead to inconsistent waveguide transmission and coupling losses. Trajectory-symmetry designs are inefficient for selective-mode excitation. Therefore, we optimised the design using trajectory asymmetry with uniform waveguides and fabricated superior ultrafast laser-inscribed photonic-lantern mode (de)multiplexers. Consistent waveguide transmission and coupling losses (0.1 dB/cm and 0.2 dB/facet, respectively) at 1550 nm were obtained on uniform single-mode waveguides. Based on the trajectory-asymmetry design for photonic-lantern mode (de)multiplexers, efficient mode excitation (

,

, and

) with average insertion losses as low as 1 dB at 1550 nm was achieved, with mode-dependent losses of less than 0.3 dB. The photonic-lantern design was polarisation-insensitive, and the polarisation-determined losses were less than 0.2 dB. Along with polarisation multiplexing realised by fibre-type polarisation beam splitters, six signal channels (

,

,

,

,

, and

), each carrying 42 Gaud/s quadrature phase-shift keying signals, were transmitted through a few-mode fibre for optical transmission. The average insertion loss of the system is less than 5 dB, while its maximum crosstalk with the few-mode fibre is less than −12 dB, leading to a 4-dB power penalty. The findings of this study pave the way for the practical application of 3D integrated photonic chips in high-capacity optical transmission systems.

Lunar sample return missions are crucial for researching the composition and origin of the Moon. In recent decades, several lunar sample return missions have been conducted, yielding abundant and valuable lunar samples. As the latest development in lunar sample returns, the Chang’e-6 mission aimed to implement lunar farside sampling. The shorter time available for sampling requires higher sampling efficiency. In this study, the main factors in the sampling site selection and sampling process are introduced and a vision-based sampling implementation is designed for the Chang’e-6 mission to significantly simplify manual operation while maintaining high sampling quality. By sufficiently leveraging the point cloud data reconstructed from the binocular camera images, autonomous terrain analysis and sample point selection are achieved. A 6D pose estimation pipeline based on point cloud registration provides a robust method for sampler pose measurement, replacing the previous manual fine-tuning process and achieving better accuracy. Owing to the well-analyzed sample points and accurate fine-tuning, the proposed approach demonstrates high accuracy in controlling the scooping depth, while significantly reducing the time cost of the sampling implementation, effectively supporting the Chang’e-6 lunar sample mission.