Internal modification of glass by ultrashort laser pulse and its application to microwelding

Characterization of Plasma in Microwelding of Glass Using Ultrashort Laser Pulse at High Pulse Repetition Rates

“…However, the quality of the pictures is not good enough to evaluate the absorption property from the pictures, because of fringe patterns appeared in the pictures. In addition, the light emission from the hot plasma can compete with the SHG Nd:YAG laser beam transmitted through the band pass filter, since rather strong plasma emission lasts between the fs-laser pulses due to the heat accumulation effect at high pulse repetition rates [14,21]. Thus pictures of the laser-induced plasma taken without SHG Nd:YAG laser are solely shown in the paper, and the evolution of free-electron density in conduction band is estimated by the simulation based on the rate equation model [10,11,22].…”

“…It is also known it takes some time of the order of ms before steady temperature distribution is established [14] with accompanying some fluctuation of laser-matter interaction [20,21]. Therefore difficulty is found to use existing pump-probe technique [9,10] for characterizing plasma at high pulse repetition rates.…”

“…However, internal modification using USLP with high pulse repetition rates is rather complicate, where the modified region with dual-structure [14], which consists of teardrop-shaped inner structure and elliptical outer structure. The laser energy is absorbed by nonlinear process in the inner structure [14], which can be much larger than focus volume of USLP.…”

“…The laser energy is absorbed by nonlinear process in the inner structure [14], which can be much larger than focus volume of USLP. Physical process in the modified region has been analysed by the experimental measurement of nonlinear absorptivity [15], and simulation based on thermal conduction model [16,17].…”

[INVITED] Ultrafast laser micro-processing of transparent material

“…The novel idea of the prebonding drastically improved the joining strength and reliability of ultrafast laser micro-welding [95,96]. Miyamoto further clarified the crackfree condition that is related to the dual-structure of the processed area [97,98]. A new idea such as the reinforced direct bonding [99] is attractive for fast and wide welding.…”