High-Repetition-Rate Ultrafast Fiber Lasers for Material Processing

Abstract

Ultrafast lasers operating at high repetition rates, in particular the GHz range, enable new possibilities in lasermaterial processing, particularly accessing the recently demonstrated ablation-cooled regime. We provide a unified perspective of the unique opportunities created by operating at high repetition rates together with our efforts into the development of enabling laser technology, including new results on further scaling up the capabilities of the laser systems. In order to access GHz repetition rates and microjoule-level pulse energies without requiring kilowatts of average power, we implement burst-mode operation. Our results can be grouped into two distinct directions: low-and highpower systems. Pulsed pumping is employed in the later stages of low-power systems, which have low burst repetition rates to achieve high pulse energies, whereas the technique of doping management is developed for the continuously pumped power amplifier stage of high power systems. While most of the developments have been at 1-µm wavelength range due to the relative maturity of the laser technology, we also report the development of Tm-fiber lasers around the 2-µm region specifically for tissue processing and laser-surgery applications.

Ultra-Short Pulse Lasers for Microfabrication: A Review

“…Ultra-high pulse repetition rate is a way of upscaling the process efficiency. The laser could be implemented in the burst mode to access GHz repetition rates and microjoule-level pulse energies without requiring kilo-watts of average power [33]. The 2.65 GHz repetition rate bursts of ultra-short laser pulses containing a desirable number of pulses within a burst with identical pulse separation and adjustable amplitude were demonstrated in an active fiber loop [34].…”

4 mJ Rectangular- Envelope GHz-Adjustable Burst-Mode Fiber-Bulk Hybrid Laser and Second-Harmonic Generation

“…To produce sufficient peak power and offer flexibility of pulse parameters, almost all of the burst-mode laser systems involve a master oscillator power amplifier (MOPA) configuration [15][16][17][18][19][20][21][22][23][24]. To generate the burst-mode seeds, time gating high repetition rate mode-locked or gain-switched pulses is one popular method [15][16][17][18]. Besides, mode-locked ultrafast laser and time gate could achieve ultrafast (such as ~fs) burst laser [15][16].…”

“…To generate the burst-mode seeds, time gating high repetition rate mode-locked or gain-switched pulses is one popular method [15][16][17][18]. Besides, mode-locked ultrafast laser and time gate could achieve ultrafast (such as ~fs) burst laser [15][16]. In addition, pulse stacking could produce the burst-mode pulses with complexity [19][20].…”

Twelve-Wavelength-Switchable Thulium-Doped Fiber Laser With a Multimode Fiber Bragg Grating

“…Thus, the TDFL is well suited for cutting and vaporizing biological tissue [7], [8]. Furthermore, the TDFL has wide applications, such as in material processing [9], coherent Doppler lidar [10] and pump source in generating Mid-Infrared Super Continuum [11]. Thus, the TDFL is currently in great demand and needs to be further developed.…”