The application of modern technology is a key breakthrough in the current global protection of cultural relics. Among them, laser cleaning technology for cultural relics has become a revolutionary tool in the field of cultural heritage restoration due to its non-contact, high-precision, and environmentally friendly characteristics. The principle and development of laser cleaning technology Laser cleaning technology is a non-contact cleaning technology that utilizes the photothermal or optomechanical effects generated by the interaction between laser beams and materials to selectively remove surface pollutants from materials. The core principle can be summarized as "selective photothermal effect", which means that different substances have significant differences in the absorption rate of specific wavelength lasers. By precisely controlling the laser wavelength, energy density, and pulse frequency, it is possible to achieve precise removal of pollutants without damaging the cultural relics themselves. In the 1970s, American scientists such as Asums believed that lasers could be used to clean ancient murals and sculptures, and for the first time, they conducted a series of cleaning experiments on the hard shell pollutants on the stone surface of Venice, thus opening up the application of laser cleaning technology in the field of cultural relic protection. In the 1980s, with the rapid development of laser technology, European countries began to apply this technology to the protection of stone cultural relics. Some sculptures of world-renowned landmarks such as Amiens Cathedral in France, Cologne Cathedral in Germany, and Stephen's Cathedral in Austria have been restored to their former glory through laser cleaning technology. After more than 30 years of development, modern laser cleaning technology has achieved a technological leap from nanosecond to femtosecond ultra short pulses, with cleaning accuracy reaching the micrometer level. Compared with traditional cleaning methods, laser cleaning has revolutionary advantages: non-contact operation avoids physical friction damage, sub micron precision is suitable for cleaning complex patterns, no chemical reagent residue effectively avoids secondary damage, and the cleaning process can be monitored in real time. These characteristics make it a "precision surgical knife" in the field of modern cultural relic protection. Since 2000, there have been many successful cases of laser cleaning technology in the field of cultural preservation. Among them, the femtosecond laser system developed by the Electronic Structure and Laser Research Institute of the Greek Research and Technology Foundation successfully removed stubborn crusts on the marble components of the Acropolis in Athens. It has successively completed the cleaning work of precious cultural relics such as the wall sculptures of the Parthenon Temple, the Fritz sculptures of the Winged Victory Goddess Temple, and the roof of the portico of the Erechtion Temple. In addition, the mobile laser equipment of Italian OPTO company has been widely used in the protection of Pompeii ancient city murals, and the British Museum has established a complete laser cleaning parameter database... Laser cleaning technology has become an important technical means in the field of world cultural heritage. The best choice to balance safety and effectiveness is in the Temple of Erechtion on the Acropolis in Athens, where six female statues with a history of over 2400 years were once deeply affected by the erosion crisis of black crust. These marble statues have undergone three repairs, but the sulfide deposition caused by the intensification of Athens' industrialization in the 1950s resulted in their surface being covered by a dense black shell, gradually blurring the details. In 2010, the Acropolis Museum and the Greek Institute of Electronic Structures and Laser Research team innovatively used a combination of 1064nm infrared and 355nm ultraviolet dual wavelength laser technology to accurately layer and remove pollutants. Infrared laser reduces the thickness of the black shell, and ultraviolet laser removes residual particles, which not only avoids the damage of traditional cleaning to marble, but also cleverly avoids the risk of substrate yellowing. The Diocletian Palace in the ancient city of Split, Croatia has a history of over 1700 years, with 16 towers and 4 palace gates. The two 11 meter wide arcades located in the center of the palace attract tourists from all over the world to stop and admire. However, its iconic milky white arches and stone pillars have turned black over time. In the late 19th to mid-20th century, nearby industrial smoke and dust further obscured the unique style and decorations of the building, with dirt accumulating in some areas up to several centimeters thick. The excessively heavy attachments make traditional cleaning methods prone to damage the building itself, resulting in the loss of cultural relics details. Since 2010, local cultural relic protectors have pioneered the use of laser cleaning technology to "wash away the millennium dust" of this 4th century Roman palace. This is the first large-scale stone building laser cleaning work carried out in Europe, and the entire project took ten years, demonstrating its technological advantages in complex scenes. In 2012, the Louvre Museum in France exhibited Leonardo da Vinci's posthumous work "Madonna, Child, and Saint Anne", which had undergone laser cleaning on the surface. The three characters in the painting were "liberated" from the dull and gloomy tones. Laser technology accurately removes pollutants, reproducing delicate and layered tones in the image, becoming a classic case of oil painting restoration. The murals of the "Mysterious Manor" in the ancient city of Pompeii, Italy, are mottled due to volcanic ash coverage. The laser penetrates surface impurities and restores the original magnificent colors of the mural without damaging the pigment. It has been evaluated by the Italian Department of Cultural Heritage as the "best choice to balance safety and effectiveness". Despite the significant advantages of laser cleaning technology, its application still faces challenges due to technological breakthroughs and global collaboration. In terms of material adaptability, different materials will have different performances after laser cleaning. For example, the mature laser cleaning technology in Europe will cause yellowing when cleaning White Marble materials in China. In September 2020, under the guidance of the Ministry of Science and Technology and the recommendation of the Ministry of Culture and Tourism, the "China Greece Joint Laboratory for Cultural Relics Protection Technology 'the Belt and Road'" jointly applied by the Chinese Palace Museum and the Greek Electronic Structure and Laser Research Institute under the Greek Research and Technology Foundation was officially approved for construction, creating a new model of cultural protection technology innovation under the "the Belt and Road" framework. The Zhongxi team has tackled this technical challenge by adjusting multi wavelength combinations or auxiliary reagents, using ultra short pulse (picosecond laser) technology to reduce thermal effects and avoid substrate damage. In addition, the lack of standardization is a difficulty in promoting laser cleaning technology at present. Different cultural relics require customized parameters to facilitate practical operations by different departments. The laser holographic speckle interferometry device jointly developed by Shanghai University and IESL in Greece can detect micro cracks on the sub surface of cultural relics and provide quantitative basis for disease warning. Currently, various modern technologies are developing rapidly, and the integration of laser cleaning with other technologies is an important trend. In the Pompeii Ancient City project in Italy, the linkage of laser and hyperspectral imaging technology not only makes the restoration process quantifiable and traceable, but also establishes a full process management of "diagnosis repair monitoring", providing a model for technological collaboration and injecting technological momentum into the inheritance and development of cultural heritage. Laser cleaning technology transcends time and space, becoming a bridge for dialogue between Eastern and Western civilizations. The protection of cultural heritage is not only a technical issue, but also a practice of mutual learning among civilizations. In the future, with the intelligence of technology and the globalization of collaboration, laser cleaning technology will undoubtedly inject more wisdom and strength into the sustainable inheritance of human cultural heritage. (New Society)