Quarter Century Development of Laser Peening and Recent Strides toward Expansion of Applications

Underwater laser ablation with nanoseconds lasers generates high-pressure plasma exceeding GPa, and can be used as a hammer to forge the surface of most metals. This technology is known as laser peening (LP) and has been used in aeronautical and nuclear industries since the late 1990s. Most recently, we have developed a novel LP process without water by using a femtosecond laser, which extends the application to integrated systems with mechanics and electronics incompatible with aqueous environment, and even to components in space. Various applications would be realized by enhancing usability through miniaturization and simplification. In this context, we have developed ultra-compact handheld microchip lasers with passive Q-switch generating sub-nanosecond pulses, which paves the way to a wide range of new applications beyond the horizons posed by current laser systems.