We have built a fs laser welding setup with a custom built fs laser having adjustable parameters integrated to a scanning scheme including a linear translation stage and a simple stepper motor to obtain spiral scanning. We have obtained successful results with both raster scan and spiral scan using borofloat glass samples and compared them in terms of homogeneity and total elapsed time. We obtained better results in the case of spiral scanning. The modifications that have formed during spiral scanning were more homogeneous owing to the continuous motion between the start and end points and no apparent stress load were visible. We also investigated parameter space by adjusting rotation frequency and translation velocity and achieved successful welding results with 750 mm/s linear velocity, having >509.19 mm/s/W efficiency. These are the highest speed and efficiency welding results to our knowledge.
High quality thin glasses are emerging materials that find vast areas of applications in screen technologies, VR, microfluidics and solar cells. Due to the density of the glass material and the miniaturization trend in devices, thinner glasses are needed in the industry. Hence, in high-tech applications glasses and devices thin glasses are mostly used after a tempering process to achieve durability needed by the application. Some of the applications and design geometries necessitate these glasses to be welded. But due to the balance between compressive strength and tension inside glass is very delicate, laser processing of tempered glass is risky and may cause the glass to shatter if this balance is disturbed during a laser processing. Here we report, to our knowledge, first tempered glass welding of chemically tempered glasses using fs pulsed laser. We developed a fs laser system with adjustable parameters and integrated with a spiral scanning system to keep the stress load at minimum to prevent the shattering of the tempered glass due to stress. We observed successful welded regions in mm2 areas, by keeping the glasses transparent and intact.
We report an Yb-doped fiber laser oscillator that is generating femtosecond pulses with tunable spectral properties. Central wavelength and the bandwidth of the oscillator is adjusted via a manual iris aperture used as a spatial filter in the laser cavity. The tunability range of the central wavelength of the optical pulses generated from the oscillator is in the range of 1022 nm to 1038 nm and the bandwidth tunability range is 8 nm to 32 nm. The obtained pulses are all suitable for further amplification via fiber-based amplifiers and mostly in the mW average power range. The adjustability is satisfied by changing the aperture width and the system is open for improvement by adjusting the position of the filter too. We believe that this tunable oscillator is promising to be used as a seed for high power femtosecond pulse amplification schemes that necessitate certain central wavelength and bandwidth properties at the input of the amplifier and may enable more efficient and shorter pulse duration systems.
Since recently researchers at UFOLAB Group, Bilkent University discovered a new regime of ultrafast laser material processing which they named ablation-cooled material removal that utilizes very high repetition rate pulses [1], ultrashort pulses at GHz repetition rates have been attracting a lot of attention with respect to industrial material processing. Ablation cooling here refers to the method which has been used for the atmospheric reentry of rockets since 1950’s where a sacrificial layer is used to protect the rockets from burning and as a term it was first used in a 1934 novel “Triplanetary,” by E.E. ‘Doc’ Smith. In this regime, cooling of the material takes place simultaneously with ablation under the bombardment of pulses repeated with a period short enough so that relatively limited heat diffusion can take place from the targeted area to the surroundings. The targeted material heats with each successive pulse up to the critical temperature required for the evaporative removal, and the ablation takes place removing a major portion of the thermal energy localized at the targeted spot.
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