This review examines the state-of-the-art in spatial manipulation of ultrafast laser processing using dynamic light modulators, with a particular focus on liquid crystal-based systems. We discuss phase modulation strategies and highlight the current limitations and challenges in surface and bulk processing. Specifically, we emphasize the delicate balance between high-fidelity beam shaping and energy efficiency, both critical for surface and bulk processing applications. Given the inherent physical limitations of spatial light modulators such as spatial resolution, fill factor, and phase modulation range. We explore techniques developed to bridge the gap between desired intensity distributions and actual experimental beam profiles. We present various laser light modulation technologies and the main algorithmic strategies for obtaining modulation patterns. The paper includes application examples across a wide range of fields, from surgery to surface structuring, cutting, bulk photo-inscription of optical functions, and additive manufacturing, highlighting the significant enhancements in processing speed and precision due to spatial beam shaping. The diverse applications and the technological limitations underscore the need for adapted modulation pattern calculation methods. We discuss several advancements addressing these challenges, involving both experimental and algorithmic developments, including the recent incorporation of artificial intelligence. Additionally, we cover recent progress in phase and pulse front control based on spatial modulators, which introduces an extra control parameter for light excitation with high potential for achieving more controlled processing outcomes.

Quantitative phase imaging (QPI) enables non-invasive cellular analysis by utilizing cell thickness and refractive index as intrinsic probes, revolutionizing label-free microscopy in cellular research. Differential phase contrast (DPC), a non-interferometric QPI technique, requires only four intensity images under asymmetric illumination to recover the phase of a sample, offering the advantages of being label-free, non-coherent and highly robust. Its phase reconstruction result relies on precise modeling of the phase transfer function (PTF). However, in real optical systems, the PTF will deviate from its theoretical ideal due to the unknown wavefront aberrations, which will lead to significant artifacts and distortions in the reconstructed phase. We propose an aberration-corrected DPC (ACDPC) method that utilizes three intensity images under annular illumination to jointly retrieve the aberration and the phase, achieving high-quality QPI with minimal raw data. By employing three annular illuminations precisely matched to the numerical aperture of the objective lens, the object information is transmitted into the acquired intensity with a high signal-to-noise ratio. Phase retrieval is achieved by an iterative deconvolution algorithm that uses simulated annealing to estimate the aberration and further employs regularized deconvolution to reconstruct the phase, ultimately obtaining a refined complex pupil function and an aberration-corrected quantitative phase. We demonstrate that ACDPC is robust to multi-order aberrations without any priori knowledge, and can effectively retrieve and correct system aberrations to obtain high-quality quantitative phase. Experimental results show that ACDPC can clearly reproduce subcellular structures such as vesicles and lipid droplets with higher resolution than conventional DPC, which opens up new possibilities for more accurate subcellular structure analysis in cell biology.

Accurate and real-time detection of hydrogen (H₂) is essential for ensuring energy security. Fiber-optic H₂ sensors are gaining attention for their integration and remote sensing capabilities. However, they face challenges, including complex fabrication processes and limited response times. Here, we propose a fiber-optic H₂ sensing tip based on Tamm plasmon polariton (TPP) resonance, consisting of a multilayer metal/dielectric Bragg reflector deposited directly on the fiber end facet, simplifying the fabrication process. The fiber-optic TPP (FOTPP) tip exhibits both TPP and multiple Fabry-Perot (FP) resonances simultaneously, with the TPP employed for highly sensitive H₂ detection. Compared to FP resonance, TPP exhibits more than twice the sensitivity under the same structural dimension without cavity geometry deformation. The excellent performance is attributed to alterations in phase-matching conditions, driven by changes in penetration depth of TPP. Furthermore, the FP mode is utilized to achieve an efficient photothermal effect to catalyze the reaction between H₂ and the FOTPP structure. Consequently, the response and recovery speeds of the FOTPP tip under resonance-enhanced photothermal assistance are improved by 6.5 and 2.1 times, respectively. Our work offers a novel strategy for developing TPP-integrated fiber-optic tips, refines the theoretical framework of photothermal-assisted detection systems, and provides clear experimental evidence.

With the rapid development of lithium batteries, it’s of great significance to ensure the safe use of it. An ultrasound imaging system based on fiber optic ultrasound sensor has been developed to monitor the internal changes of lithium batteries. Based on Fabry-Perot interferometer (FPI) structure which is made of a glass plate and an optical fiber pigtail, the ultrasound imaging system possesses a high sensitivity of 558 mV/kPa at 500 kHz with the noise equivalent pressure (NEP) of only 63.5 mPa. For the frequency response, the ultrasound sensitivity is higher than 13.1 mV/kPa within the frequency range from 50 kHz to 1 MHz. Meanwhile, the battery imaging system based on the proposed sensor has a superior resolution as high as 0.5 mm. The performance of battery safety monitoring is verified, in which three commercial lithium-ion ferrous phosphate/graphite (LFP||Gr) batteries are imaged and the state of health (SOH) for different batteries is obtained. Besides, the wetting process of an anode-free lithium metal batteries (AFLMB) is clearly observed via the proposed system, in which the formation process of the pouch cell is analyzed and the gas-related "unwetting" condition is discovered, representing a significant advancement in battery health monitoring field. In the future, the commercial usage can be realized when sensor array and artificial intelligence technology are adopted.

Ultrasonic neuromodulation has gained recognition as a promising therapeutic approach. A miniature transducer capable of generating suitable-strength and broadband ultrasound is of great significance for achieving high spatial precision ultrasonic neural stimulation. However, the ultrasound transducer with the above integrated is yet to be challenged. Here, we developed a fiber-optic photoacoustic emitter (FPE) with a diameter of 200 μm, featuring controllable sound intensity and a broadband response (−6 dB bandwidth: 162%). The device integrates MXene (Ti₃C₂T_x), known for its exceptional photothermal properties, and polydimethylsiloxane, which offers a high thermal expansion coefficient. This FPE, exhibiting high spatial precision (lateral: 163.3 μm, axial: 207 μm), is capable of selectively activating neurons in targeted regions. Using the TetTagging method to selectively express a cfos-promoter-inducible mCHERRY gene within the medial prefrontal cortex (mPFC), we found that photoacoustic stimulation significantly and temporarily activated the neurons. In vivo fiber photometry demonstrated that photoacoustic stimulation induced substantial calcium transients in mPFC neurons. Furthermore, we confirmed that photoacoustic stimulation of the mPFC using FPE markedly alleviates acute social defeat stress-induced emotional stress in mice. This work demonstrates the potential of FPEs for clinical applications, with a particular focus on modulating neural activity to regulate emotions.

Color as an indispensable element in our life brings vitality to us and enriches our lifestyles through decorations, indicators, and information carriers. Structural color offers an intriguing strategy to achieve novel functions and endows color with additional levels of significance in anti-counterfeiting, display, sensor, and printing. Furthermore, structural colors possess excellent properties, such as resistance to extreme external conditions, high brightness, saturation, and purity. Devices and platforms based on structural color have significantly changed our life and are becoming increasingly important. Here, we reviewed four typical applications of structural color and analyzed their advantages and shortcomings. First, a series of mechanisms and fabrication methods are briefly summarized and compared. Subsequently, recent progress of structural color and its applications were discussed in detail. For each application field, we classified them into several types in terms of their functions and properties. Finally, we analyzed recent emerging technologies and their potential for integration into structural color devices, as well as the corresponding challenges.