Thin-disk Multipass Amplifier Research Articles

Compact 20-pass thin-disk multipass amplifier stable against thermal lensing effects and delivering 330 mJ pulses with M2 < 1.17.

We report on an Yb:YAG thin-disk multipass amplifier delivering 100 ns long pulses at a central wavelength of 1030 nm with an energy of 330 mJ at a repetition rate of 100 Hz. The beam quality factor at the maximum energy was measured to be M2 < 1.17. The small signal gain is 21.7, and the gain at 330 mJ was measured to be 6.9. The 20-pass amplifier is designed as a concatenation of stable resonator segments in which the beam is alternately Fourier transformed and relay-imaged back to the disk by a 4f-imaging optical scheme stage. The Fourier transform propagation makes the output beam robust against spherical phase front distortions, while the 4f-stage is used to compensate the thermal lens of the thin-disk and to reduce the footprint of the amplifier.

Thin-disk multi-pass amplifier for kilowatt-class ultrafast lasers

Abstract We report on an improved ytterbium-doped yttrium aluminum garnet thin-disk multi-pass amplifier for kilowatt-level ultrafast lasers, showcasing excellent beam quality. At a repetition rate of 800 kHz, the 6.8 ps, 276 W seed laser is amplified up to an average power of 1075 W, corresponding to a pulse energy of 1.34 mJ. The 36-pass amplifier is designed as a compact mirror array in which the beam alternately propagates between the mirrors and the disk by a quasi-collimated state. We adopted a quasi-collimated propagation to confine stray and diffracted light by the slight curvature of the disk, which enables us to achieve an outstanding extraction efficiency of up to 57% with excellent beam quality in stable laser operation at high power. The beam quality at 1075 W was measured to be M2 &lt; 1.51. Furthermore, stability testing was demonstrated with a root-mean-square power fluctuation of less than 1.67% for 10 min.

Thin-disk multipass amplifier delivering sub-400 fs pulses with excellent beam quality at an average power of 1 kW

We present an improved multipass amplifier design, enabling the amplification of ultrashort pulses with excellent beam quality to more than 1 kW of average output power. 260 fs short pulses at an average power of 105 W and a repetition rate of 1 MHz were directly amplified up to an average power of 1033 W. The pulse duration at this power level was measured to be 388 fs assuming a Gaussian temporal shape. This corresponds to a peak power of 2.5 GW. The power stability was measured to be 0.16% RMS over a duration of more than two hours at a sampling rate of 2 Hz. High beam quality is proven with measured values of M x 2 = 1 .16 in the horizontal and M y 2 = 1 .19 in the vertical plane according to ISO Standard 11146.

Azimuthally polarized picosecond vector beam with 1.7 kW of average output power.

We report on a thin-disk multipass amplifier delivering azimuthally polarized, 7.8 ps short, laser pulses at an average power and with pulse energies of up to 1.7 kW and 5.8 mJ, respectively. High polarization purity was achieved by compensating for the arbitrary linear phase shifts that are introduced by tilted optical elements.

Thin-disk laser system operating above 10 kW at near fundamental mode beam quality.

We report on a thin-disk laser system with more than 10 kW of output power and a beam quality of M2=1.76 at an overall optical-to-optical efficiency of 51%. The system consists of two thin-disk laser oscillators and a thin-disk multi-pass amplifier system. To reach high output powers while maintaining good beam quality, the output beams of two identical laser oscillators are polarization-combined. Subsequently, the beam is amplified in a multi-pass system. To the best of our knowledge, this is the highest output power achieved for a thin-disk laser system with a beam quality close to fundamental mode.

Ultrafast green thin-disk laser exceeding 1.4 kW of average power.

We present an ultrafast laser with a near-diffraction-limited beam quality delivering more than 1.4 kW of average power in the visible spectral range. The laser is based on second harmonic generation in a lithium triborate crystal of a Yb:YAG thin-disk multipass amplifier emitting more than 2 kW of average power in the infrared.

Ultrafast thin-disk multipass amplifier with 720mJ operating at kilohertz repetition rate for applications in atmospheric research.

We present an ultrafast thin-disk based multipass amplifier operating at a wavelength of 1030 nm, designed for atmospheric research in the framework of the Laser Lightning Rod project. The CPA system delivers a pulse energy of 720 mJ and a pulse duration of 920 fs at a repetition rate of 1 kHz. The 240 mJ seed pulses generated by a regenerative amplifier are amplified to the final energy in a multipass amplifier via four industrial thin-disk laser heads. The beam quality factor remains ∼ 2.1 at the output. First results on horizontal long-range filament generation are presented.

Ultrafast thin-disk multi-pass amplifier system providing 1.9 kW of average output power and pulse energies in the 10 mJ range at 1 ps of pulse duration for glass-cleaving applications.

An ultrafast Yb-doped thin-disk multi-pass laser amplifier system with flexible parameters for material processing is reported. We can generate bursts consisting of four pulses at a distance of 20 ns and a total energy of 46.7 mJ at a repetition rate of 25 kHz. In single-pulse operation, 1.5 kW of average output is achieved at 400 kHz when optimizing for a beam quality of M2 = 1.5. Alignment for maximum output power provides 1.9 kW at the same repetition rate. All results are obtained without chirped-pulse amplification in the multi-pass set-up. The application potential of the system is demonstrated exploring its performance in materials processing of dielectrics. Cleaving of 3.8-mm-thick SCHOTT borofloat glass with a velocity of 1200 mm/s is demonstrated with 300 W of input power. Single-pass modification of 30 mm borosilicate glass is enabled with a Bessel beam at 1 kW of average power delivered by four-pulse bursts of an energy of 30 mJ.

Direct amplification of sub-300 fs pulses in a versatile thin-disk multipass amplifier

We report on a kW-class ultrafast laser amplifier emitting sub-300 fs pulses with a pulse peak power exceeding 1 GW. It is based on the direct amplification of 260 fs pulses in a versatile thin-disk multipass amplifier which provides fast modulation of the amplified beam on the workpiece by the implementation of a novel and robust polarization multiplexing scheme for the seed beam that is launched into the amplifier. Furthermore, the laser can be operated in a single-pulse or burst mode with a variable number of pulses per burst. Second harmonic conversion of the amplified beam by means of a lithium triborate crystal additionally led to an output power of up to 282 W in the green spectral range.

Exploiting nonlinear spectral broadening in a 400 W Yb:YAG thin-disk multipass amplifier to achieve 2 mJ pulses with sub-150 fs duration

Abstract We present investigations on the extent of spectral broadening occurring during the propagation of laser pulses in a Thin-Disk Multipass Amplifier (TDMPA) with the aim to exploit this nonlinear effect for pulse compression. The demonstrated compression of 2.05 mJ-pulses to a duration of about 136 fs FWHM at an average power of 409 W and a peak power of 9 GW is in good agreement with numerical pulse propagation simulations. Our spectral broadening and compression scheme introduced additional losses below 2%, is scalable to average powers of >1 kW with multi-mJ pulses, and strongly enhances the capabilities of ultrafast TDMPAs towards shorter pulses and higher peak powers.

Thin-disk multipass amplifier for fs pulses delivering 400 W of average and 2.0 GW of peak power for linear polarization as well as 235 W and 1.2 GW for radial polarization

We report on an Yb:YAG thin-disk multipass amplifier delivering linearly polarized laser pulses with a pulse duration of 885 fs at an average output power of 400 W and a repetition rate of 200 kHz, corresponding to a peak power of 2.0 GW. This is the highest average output power reported for thin-disk multipass amplifiers delivering pulses with peak powers in excess of 1 GW and it confirms the suitability of thin-disk multipass amplifiers to reach high average output and peak powers at the same time. The amplifier was seeded by a regenerative amplifier delivering laser pulses with a pulse duration of 805 fs and an average power of 40 W. We investigated the influence of self-phase-modulation on the amplified beam and compared it to results with lower peak intensities at a repetition rate of 800 kHz. Furthermore, we report on the amplification of a radially polarized beam leading to 235 W of average output power and 1.2 GW of peak power (at a pulse duration of 888 fs). To the best of our knowledge, this is the highest average output power demonstrated so far for radially polarized GW peak-level laser pulses.

Radially polarized emission with 635 W of average power and 2.1 mJ of pulse energy generated by an ultrafast thin-disk multipass amplifier.

We report on a thin-disk multipass amplifier delivering radially polarized laser pulses with an average power of 635W and 2.1mJ of pulse energy. To the best of our knowledge, this is the highest average output power and pulse energy reported so far for radially polarized ultrafast lasers. The amplifier is seeded by a TruMicro5050 with 115W of average output power, 6.5ps pulse duration, and a repetition rate of 300kHz. A segmented half-waveplate was used for converting the linearly polarized beam into radial polarization in front of the amplifier. We present a scheme for direct amplification of such doughnut-shaped radially-polarized beams, the results obtained, and a solution to compensate for the depolarizing phase shift introduced by the tilted mirrors in the amplifier.

11 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.

Pulsed operation of a high average power Yb:YAG thin-disk multipass amplifier

An Yb:YAG thin-disk multipass laser amplifier system was developed operating in a 10 Hz burst operation mode with 800 µs burst duration and 100 kHz intra-burst repetition rate. Methods for the suppression of parasitic amplified spontaneous emission are presented. The average output pulse energy is up to 44.5 mJ and 820 fs compressed pulse duration. The average power of 4.45 kW during the burst is the highest reported for this type of amplifier.