RESUMO
Today, glass and other similar dielectric materials are widely used in modern manufacturing. However, glass is a brittle and a heat sensitive material. Laser technology is used to process glass but quality and throughput are still a key issue. In the present paper, we investigate dual-wavelength double ultrashort laser pulses in order to control free electrons dynamics and subsequent ablation for fused silica processing, and further improve the understanding of this laser-material interaction. We used a high average power Yb-doped femtosecond laser source (100 W) with two optical lines exhibiting different pulse durations and wavelengths (500 fs at 515 nm; and 1 or 10 ps at 1030 nm) with various fluences and delays. The best configuration in terms of ablation efficiency is expected to take place when the green pulse first induces free electrons, followed by their heating by the red pulse. The obtained results are discussed in terms of optical transmission as well as ablated volume, and are compared with single pulse ablation. Our experimental results are supported by absorbed energy density calculations based on a model considering the two-color laser induced electron dynamics, including photoionization, laser heating of free electrons, and their recombination. We demonstrate that there is an optimal cooperating effect between the two sub-pulses for a 1-ps delay, nevertheless there is no beneficial effect in splitting the beam for optimizing fused silica ablation compared with the single-pulse green configuration.
RESUMO
A mode-locked thin-disk laser based on Yb:CALGO is demonstrated for the first time. At an average output power of 28 W we obtained pulses with a duration of 300 fs and a pulse energy of 1.3 µJ. 197 fs pulses with 0.9 µJ of energy were achieved at an average output power of 20 W. The shortest pulse duration measured in our experiments was 135 fs with a spectrum centered at 1043 nm. The experiments also revealed a very broad tunability from 1032 to 1046 nm with sub-200 fs pulses.
RESUMO
Using passive coherent beam combining of two ultrafast fiber amplifiers, we demonstrate the generation of high temporal quality 300 fs and 650 µJ pulses corresponding to 60 W of average power at a repetition rate of 92 kHz. Furthermore, at 2 MHz of repetition rate record coherent combining average powers of 135 W before and 105 W after compression are measured. A combining efficiency higher than 90% is maintained over the whole range of output powers and repetition rates investigated demonstrating the efficiency and robustness of the passive combining technique. The measured pulse-to-pulse relative power fluctuation at high energy is 2%, indicating that the system is essentially immune to environmental phase noise. We believe the passive combining method to be an attractive approach for compact multi-GW peak power femtosecond fiber-based sources.
RESUMO
We report on the rare-earth-doped fiber-based generation of nearly transform-limited 10-ps pulses based on self-phase-modulation-induced spectral compression. An ytterbium-doped low nonlinearity photonic crystal fiber is used as a gain medium. An average power of as much as 97 W at a repetition rate of 47 MHz, corresponding to a peak power as high as 200 kW, was obtained. Furthermore, efficient second-harmonic generation by application of this high-power laser source is discussed.
RESUMO
We demonstrate a passively mode-locked diode-pumped thin-disk Yb:YAG laser generating 810-fs pulses at 1030 nm with as much as 60 W of average output power (without using an amplifier). At a pulse repetition rate of 34.3 MHz, the pulse energy is 1.75 microJ and the peak power is as high as 1.9 MW. The beam quality is close to the diffraction limit, with M2 < 1.1.
RESUMO
A diode-pumped Yb>(3+):Ca(4)GdO(BO>(3))(3) (Yb:GdCOB) laser generating 90-fs pulses at a center wavelength of 1045 nm is demonstrated. This is, to our knowledge, the shortest pulse duration obtained from an ytterbium laser with a crystalline host. This laser is mode locked with a high-finesse semiconductor saturable-absorber mirror and emits 40 mW of average power at a repetition rate of 100 MHz.
RESUMO
An Yb:glass regenerative amplifier directly side pumped by four 20-W diodes is demonstrated. By use of a novel pumping scheme and introduction of cylindrical optics into the cavity, a free-running average output power as great as 4 W with a TEM(00) -like mode was achieved from the bare cavity, with a 0.56 pump duty cycle. When the regenerative amplifier injected, 1-mJ 200-fs FWHM pulses were obtained following compression by use of 2-ms pump pulses and up to a 150-Hz repetition rate.
RESUMO
We obtained 74-kW peak power and 3.5-W average output power in 1-ps pulses from a diode-pumped Yb:YAG laser at 1030 nm that was passively mode locked with a semiconductor saturable-absorber mirror. Another laser produced 57-kW peak power and as much as 8.1-W average output power in 2.2-ps pulses, split into two nearly diffraction-limited beams (M(2)<1.2) . To our knowledge, these are by far the highest reported peak and average output powers from a diode-pumped mode-locked laser in this pulse-duration regime.
RESUMO
Diode-pumped Yb:phosphate and Yb:silicate glass lasers have been passively mode locked for the first time to the authors' knowledge. Reliable self-starting mode locking without critical cavity alignment has been achieved with intracavity semiconductor saturable-absorber mirrors and soliton mode locking. We generated pulses as short as 58 fs with the Yb:phosphate laser and 61 fs with the Yb:silicate laser at average output powers of 65 and 53 mW, respectively. The pulse repetition rate was 112 MHz. Additionally, we demonstrated tunability of femtosecond pulses from 1025 to 1065 nm for the Yb:phosphate and from 1030 to 1082 nm for the Yb:silicate glasses. The highest mode-locked output power was 405 mW, with 183-fs pulses from the phosphate glass. The diode pump power was 1.68 W, corresponding to 24% optical-to-optical efficiency. The highest cw output power was 510 mW at the same incident pump power.
