Alexander Killi

Er:Yb-doped waveguide laser fabricated by femtosecond laser pulses

Laser action is demonstrated in a 20-mm-long waveguide fabricated on an Er:Yb-doped phosphate glass by femtosecond laser pulses. An output power of 1.7 mW with approximately 300 mW of pump power coupled into the waveguide is obtained at 1533.5 nm. Waveguides are manufactured with the 520-nm radiation from a frequency-doubled, diode-pumped, cavity-dumped Yb:glass laser operating at a 166-KHz repetition rate, with a 300-fs pulse duration.

High-repetition-rate picosecond pump laser based on a Yb:YAG disk amplifier for optical parametric amplification

We report an optically synchronized picosecond pump laser for optical parametric amplifiers based on an Yb:YAG thin-disk amplifier. At 3 kHz repetition rate, pulse energies of 25 mJ with 1.6 ps pulse duration were achieved with an rms fluctuation in pulse energy of <0.7% by utilizing a broadly intermittent single-energy regime in the deterministic chaos of a continuously pumped regenerative amplifier.

Subpicosecond thin-disk laser oscillator with pulse energies of up to 25.9 microjoules by use of an active multipass geometry

The pulse shaping dynamics of a diode-pumped laser oscillator with active multipass cell was studied experimentally and numerically. We demonstrate the generation of high energy subpicosecond pulses with a pulse energy of up to 25.9 microJ at a pulse duration of 928 fs directly from a thin-disk laser oscillator. These results are achieved by employing a selfimaging active multipass geometry operated in ambient atmosphere. Stable single pulse operation has been obtained with an average output power in excess of 76 W and at a repetition rate of 2.93 MHz. Self starting passive mode locking was accomplished using a semiconductor saturable absorber mirror. The experimental results are compared with numerical simulations, showing good agreement including the appearance of Kelly sidebands. Furthermore, a modified soliton-area theorem for approximating the pulse duration is presented.

1.1 kW average output power from a thin-disk multipass amplifier for ultrashort laser pulses

We report on a thin-disk multipass amplifier for ultrashort laser pulses delivering an average output power of 1105 W. The amplifier was seeded by a Trumpf TruMicro5050 laser with a power of 80 W at a wavelength of 1030 nm, pulse duration of 6.5 ps, and repetition rate of 800 kHz. The energy of the amplified pulses is 1.38 mJ with a duration of 7.3 ps. The amplifier exhibits an optical efficiency of 44% and a slope efficiency of 46%. The beam quality was measured to be better than M²=1.25.

Mode-locked Yb:YAG thin-disk oscillator with 41 µJ pulse energy at 145 W average infrared power and high power frequency conversion

We demonstrate the generation of 1.1 ps pulses containing more than 41 µJ of energy directly out of an Yb:YAG thin-disk without any additional amplification stages. The laser oscillator operates in ambient atmosphere with a 3.5 MHz repetition rate and 145 W of average output power at a fundamental wavelength of 1030 nm. An average output power of 91.5 W at 515 nm was obtained by frequency doubling with a conversion efficiency exceeding 65%. Third harmonic generation resulted in 34 W at 343 nm at 34% efficiency.

Waveguide lasers in the C-band fabricated by laser inscription with a compact femtosecond oscillator

Femtosecond laser writing of high-quality optical waveguides by means of a compact diode-pumped cavity-dumped Yb:glass laser oscillator is reported. Waveguides have been written on an erbium-ytterbium co-doped phosphate glass for active device production. A detailed analysis of the optical characteristics of waveguides written with different repetition rates, pulse energies, and translation speeds is presented, and an optimum set of writing parameters is established. Coupling losses as low as 0.1 dB/facet with standard telecom fibers and propagation losses lower than 0.4 dB/cm have been obtained. Characterization of the active properties of the waveguides is also presented, together with the demonstration of waveguide laser action in the whole C-band with peak output power of more than 30 mW.

Optical waveguide writing with a diode-pumped femtosecond oscillator

Optical waveguide writing is demonstrated by means of a diode-pumped cavity-dumped Yb:glass femtosecond laser oscillator with a pulse energy of 270 nJ at a 166-kHz repetition rate. Waveguides realized on an Er:Yb-doped phosphate glass are almost perfectly mode matched to standard single-mode fibers at 1.55 microm and show a 1.2-dB net gain in a standard telecommunications amplifier setup. Waveguide writing with a compact femtosecond laser oscillator is an important step toward introducing this technique into an industrial context.

High-peak-power pulses from a cavity-dumped Yb:KY(WO4)2 oscillator

We report generation of 1.35 microJ femtosecond laser pulses with a peak power of 3 MW at 1 MHz repetition rate from a diode-pumped Yb:KY(WO4)2 laser oscillator with cavity dumping. By extracavity compression with a large-mode-area fiber and a prism sequence, we generate ultrashort pulses with a duration of 21 fs and a peak power of 13 MW.

C-band waveguide amplifier produced by femtosecond laser writing

An optical waveguide amplifier fabricated on erbium-ytterbium-doped phosphate glass by direct femtosecond laser writing is demonstrated. The waveguides are manufactured using 1040-nm radiation from a diode-pumped cavity-dumped Yb:KYW oscillator, operating at a 885 kHz repetition rate, with a 350 fs pulse duration. Peak internal gain of 9.2 dB is obtained at 1535 nm, with a minimum internal gain of 5.2 dB at 1565 nm. Relatively low insertion losses of 1.9 dB enable for the first time an appreciable net gain in the full C-band of optical communications.

Ultrafast thin-disk multipass laser amplifier delivering 1.4 kW (4.7 mJ, 1030 nm) average power converted to 820 W at 515 nm and 234 W at 343 nm

We report on an Yb:YAG thin-disk multipass laser amplifier delivering sub-8 ps pulses at a wavelength of 1030 nm with 1420 W of average output power and 4.7 mJ of pulse energy. The amplifier is seeded by a regenerative amplifier delivering 6.5 ps pulses with 300 kHz of repetition rate and an average power of 115 W. The optical efficiency of the multipass amplifier was measured to be 48% and the beam quality factor was better than M2 = 1.4. Furthermore we report on the external second harmonic generation from 1030 nm to 515 nm using an LBO crystal leading to an output power of 820 W with 2.7 mJ of energy per pulse. This corresponds to a conversion efficiency of 70%. Additionally, 234 W of average power were obtained at the third harmonic with a wavelength of 343 nm.