The valve-controlled hydraulic cylinder system (VCHCS) is commonly used for actuators such as manipulators in deep-sea equipment, whose working performance is crucial to subsea tasks. Affected by the ambient pressure introduced by the pressure compensator, the viscosity of the hydraulic oil increases significantly. On this basis, the viscosity changes further when flowing in the slender pipeline, making the pipeline pressure loss substantially increase and subsequently affecting the working performance of the deep-sea VCHCS. Aiming at this issue, a detailed nonlinear mathematical model of the deep-sea VCHCS is established, in which the viscosity-pressure characteristics of the hydraulic oil is considered to take the viscosity changes in the pipeline into account. Besides, the hydrodynamic effects are also included in the model. Then the corresponding numerical simulation model of the deep-sea VCHCS is established, and its working performance at different depths is simulated and analyzed. When the depth is 11km, the extension and retraction movements are delayed by 52.50% and 43.12% respectively. The root cause of the delay is then analyzed and discussed. Finally, the parameters that affect the working performance are studied, and suggestions to reduce or eliminate the delay phenomenon are given. The results can provide theoretical support for the performance optimization of the deep-sea VCHCS.

The rise of high-performance functional devices has driven significant breakthroughs in various research fields, with ultrafast laser processing offering unprecedented opportunities for advanced device fabrication. This review summarizes recent progress and future prospects for ultrafast laser in fabricating functional optical, semiconductor, and sensor devices. Central to these advances is a deeper understanding of ultrafast laser–matter interaction physics, including nonlinear optical effects, multiphoton ionization, avalanche ionization, and laser-induced plasma dynamics. These phenomena govern carrier excitation, energy deposition, and subsequent structural modification. We further review how such interactions enable controlled refractive index changes, selective ablation, and nanoscale material structuring in photosensitive, dielectric, semiconductor, and metallic substrates. Key applications are then reviewed, including ultrafast laser fabrication of optical devices (e.g., optical waveguide devices, optical data storage elements, optical elements, and artificial compound eyes, integrated photonic devices), semiconductor devices (e.g., semiconductor light-emitting devices, photodiodes, solar cells, and photodetectors), and sensors (e.g., fiber optic sensors, flexible sensors, and biochemical sensors). Recent breakthroughs showcase ultrafast laser-induced precision in device miniaturization, improved optoelectronic characteristics, and integration of complex functions (e.g., topological photonic circuits fabricated via sub-100-nm laser writing, 5D optical data storage in glass with > 1 TB/cm3 density, perovskite solar cells achieving 25.7% efficiency through laser-induced phase engineering, alongside plasmonic biosensors with 100× sensitivity enhancement, and stretchable graphene sensors for wearables). Finally, this review discusses core challenges, such as enhancing the scalability of ultrafast laser processes for industrial-scale production and optimizing laser-material interactions to improve device reliability and performance. Future efforts should address key challenges such as the limited scalability of ultrafast laser processing and the incomplete understanding of laser–matter interactions at ultrafast timescales. Integrating ultrafast lasers with AI-driven control, beam shaping, and advanced materials such as 2D heterostructures may enable smarter and more multifunctional device platforms. A unified theoretical framework is also needed to guide precise and efficient fabrication. These directions highlight critical opportunities for bridging current limitations and enabling transformative advances. While not exhaustive, this review lays a foundation for further research into the transformative potential of ultrafast laser in functional device fabrication.