Preface to the special issue on advanced laser sensing techniques and applications

Recent advance in lasers and optoelectronic devices has opened up new opportunities for Optics and Photonics. Laser based optical and photonic techniques have become the powerful support of information technique, industry, human life and other important aspects of modern society.^1–4 This Special Issue of the journal, JOURNAL OF LASER APPLICATIONS, entitled “Advanced Laser Sensing Techniques and Applications” focused on the latest development in these fields. Here, the relevant publications are summarized in this editorial.

Laser-induced breakdown spectroscopy (LIBS) as an efficient diagnostic tool has been widely applied in various fields, such as environment, industry, biology, medicine, geology, agriculture, food, archeology, aerospace, etc. LIBS has prominent advantages of fast response, high selectivity and high sensitivity, which is suitable for solid, liquid, and gas samples with little pretreatment. In this special issue, LIBS combined with electro-deposition (ED) technique was reported by Ma et al.⁵ for detection of heavy metals in solutions, such as copper (Cu²⁺), cadmium (Cd²⁺), chromium (Cr³⁺), and nickel (Ni²⁺). The results indicated that the LIBS technique coupled with ED could be a reliable and accurate method for the detection of heavy metals in solution.

With the development of the photoelectric and optical fiber communication industries, the optical fiber sensing technique has also made great progress. Combined with spatial division multiplexing technique, fiber sensors can build large-scale sensor networks. In this field, a multiplexing method of sensor subnets for the multiparameter heterogeneous fiber sensor network (MHFSN) was proposed by Zhu et al.⁶ for improving stability and robustness of fiber sensor networks. By designing a continuous laser signal with a different wavelength in each sensor subnet, the correct recognition rate of approximate100% was achieved. The proposed MHFSN model shows a great potential for fiber sensor system stability analysis.

Laser Doppler diagnostics technique is highly attractive for real-time investigating the processes of laser evaporation of biological tissues in biomedicine, especially for laser surgery. Therefore, an overview of various aspects of self-mixing or autodyne detection of backscattered radiation for Doppler diagnostics of laser evaporation of biological and laser surgery was reported by Dmitriev et al.⁷ Laser surgical systems based on this technique can be used in the development of new approaches to precision low-traumatic and organ-saving laser operations.

The growing implementation of aluminum alloys in industry has focused interest on studying transformation processes. Laser welding is an advanced manufacturing technology that is widely applied in industry mainly due to its versatility, efficiency, and adaptability. However, internal defects that are difficult to detect, such as porosity, are one of the most critical irregularities in laser welding. For resolving this key technical issue, a porosity prediction method based on a high-speed camera monitoring system and powerful machine learning (ML) algorithms was proposed to resolve the prediction problem by Rivera et al.⁸ The proposed model and methodology indicate that they could be implemented in industrial applications for enhancing the final product quality for welded plates, reducing process waste and product quality analysis time, and increasing the operational performance of the process.

Finally, we hope this collection is enjoyed by the broad readers or researchers of laser related fields, and we would like to thank all of the authors, numerous reviewers and all the Journal staff for their great effort, and special effort for the Journal editor Prof. Yongfeng Lu and Journal Manager Alexandra Giglia, as well as our Guest Editors Prof. Kun Liu (Tianjin University) and Prof. Wei Ren (Chinese University of Hong Kong).