Koray Eken

83 W, 3.1 MHz, square-shaped, 1 ns-pulsed all-fiber-integrated laser for micromachining

We demonstrate an all-fiber-integrated laser based on off-the-shelf components producing square-shaped, 1 ns-long pulses at 1.03 μm wavelength with 3.1 MHz repetition rate and 83 W of average power. The master-oscillator power-amplifier system is seeded by a fiber oscillator utilizing a nonlinear optical loop mirror and producing incompressible pulses. A simple technique is employed to demonstrate that the pulses indeed have a random chirp. We propose that the long pulse duration should result in more efficient material removal relative to picosecond pulses, while being short enough to minimize heat effects, relative to nanosecond pulses commonly used in micromachining. Micromachining of Ti surfaces using 0.1 ns, 1 ns and 100 ns pulses supports these expectations.

Texturing of titanium (Ti6Al4V) medical implant surfaces with MHz-repetition-rate femtosecond and picosecond Yb-doped fiber lasers

We propose and demonstrate the use of short pulsed fiber lasers in surface texturing using MHz-repetition-rate, microjoule- and sub-microjoule-energy pulses. Texturing of titanium-based (Ti6Al4V) dental implant surfaces is achieved using femtosecond, picosecond and (for comparison) nanosecond pulses with the aim of controlling attachment of human cells onto the surface. Femtosecond and picosecond pulses yield similar results in the creation of micron-scale textures with greatly reduced or no thermal heat effects, whereas nanosecond pulses result in strong thermal effects. Various surface textures are created with excellent uniformity and repeatability on a desired portion of the surface. The effects of the surface texturing on the attachment and proliferation of cells are characterized under cell culture conditions. Our data indicate that picosecond-pulsed laser modification can be utilized effectively in low-cost laser surface engineering of medical implants, where different areas on the surface can be made cell-attachment friendly or hostile through the use of different patterns.

Fiber amplification of pulse bursts up to 20 μJpulse energy at 1 kHz repetition rate

We demonstrate burst-mode operation of a polarization-maintaining Yb-doped fiber amplifier. Groups of pulses with a temporal spacing of 10 ns and 1 kHz overall repetition rate are amplified to an average pulse energy of ∼20 μJ and total burst energy of 0.25 mJ. The pulses are externally compressed to ∼400 fs. The amplifier is synchronously pulsed-pumped to minimize amplified spontaneous emission between the bursts. We characterize the influence of pump pulse duration, pump-to-signal delay, and signal burst length.

Burst-mode Yb fiber amplifier producing 40 μJ individual pulse energy

We report 40-μJ individual pulse energy for 100-ns long amplified bursts with homogenized energy distribution from a 1-kHz Yb-fiber amplifier. Initial results on micromachining using burst-mode femtosecond pulses are presented for the first time.

Micromachining with square-shaped 1 ns-long pulses from an all-fiber Yb-doped laser-amplifier system

We demonstrate micromachining with 1ns-long pulses from an all-fiber laser. Fiber lasers generating uncompressible long pulses have been ignored as undesired modes, however their robust, low-repetition-rate operation is well suited to micromachining.

Burst-mode Yb fiber amplifier producing 30 μJ individual pulse energy

We report 40-μJ individual pulse energy for 100-ns long amplified bursts with homogenized energy distribution from a 1-kHz Yb-fiber amplifier. Initial results on micromachining using burst-mode femtosecond pulses are presented for the first time.

83 W, 1 ns, 3.1 MHz all-fiber laser for micromachining

Fiber lasers are commonly used for various material processing applications. The advantages (such as simplicity of the system, high material removal rate) and disadvantages (larger heat-affected zone, reduced precision) of nanosecond pulses over sub-picosecond pulses are well known.