Christian Stolzenburg

Ultrafast thin-disk Yb:KY(WO 4 ) 2 regenerative amplifier with a 200-kHz repetition rate

We report an Yb:KYW thin-disk amplifier system that provides ultrashort pulses in the 10-microJ energy range at high repetition rates. The thin-disk concept uses large laser beam cross sections to avoid high peak intensities. Without using a traditional diffraction-grating stretcher, pulse energies of approximately 9 microJ with pulse durations of 280 fs at repetition rates of 200 kHz were generated.

Recent developments in high power thin disk lasers at TRUMPF Laser

This paper highlights the latest advances of disk laser technology at TRUMPF. The disk laser combines unique properties, especially high output brilliance (at the lowest pump brilliance requirements of any high power platform), power scalability and insensitivity to back reflections. In the latest generation of CW disk lasers, 6kW are extracted from one disk in an industrial product at beam qualities suitable for cutting and welding. Laboratory results with up to 4 kW laser power at nearly diffraction limited beam quality (M2=1.38) and 8 kW with a beam quality of 3 mm mrad from a single disk and even higher output power levels with lower beam quality will be presented. Finally, results of a frequency doubled CW disk laser will be shown.

Picosecond Regenerative Yb:YAG Thin Disk Amplifier at 200 kHz Repetition Rate and 62 W Output Power

We report on a picosecond regenerative Yb:YAG thin disk amplifier capable of delivering 62 W of average output power with repetition rates up to 200 kHz and nearly diffraction-limited beam quality.

Recent disk laser development at Trumpf

This paper highlights the latest advances of disk laser technology at Trumpf. The disk laser combines unique properties, especially high output brilliance (at the lowest pump brilliance requirements of any high power platform), power scalability and broad applicability from cw to ps systems. In the new generation of cw disk lasers, 6kW are extracted from one disk in an industrial product at beam qualities suitable for welding. Moreover, scaling laser power to 10 kW per disk and resonators with higher brilliance are discussed. These advances are enabled by a combination of power scaling and increase of optical-to-optical efficiency. In addition, applications of the disk laser principle to pulsed operation, from ns to ps duration, at infrared and green wavelengths are discussed. Finally, an outlook on the capabilities of disk lasers towards highest cw power and ultra-high peak powers of petawatts and beyond is given.

The broad applicability of the Disk Laser principle — from CW to ps

The quasi two-dimensional geometry of the disk laser results in conceptional advantages over other geometries. Fundamentally, the thin disk laser allows true power scaling by increasing the pump spot diameter on the disk while keeping the power density constant. This scaling procedure keeps optical peak intensity, temperature, stress profile, and optical path differences in the disk nearly unchanged. The required pump beam brightness - a main cost driver of DPSSL systems - also remains constant. We present these fundamental concepts and present results in the wide range of multi kW-class CW-sources, high power Q-switched sources and ultrashort pulsed sources.

Cavity-dumped intracavity-frequency-doubled Yb:YAG thin disk laser with 100 W average power

We report on a cavity-dumped Yb:YAG thin disk laser with intracavity-frequency doubling to provide pulses in the millijoule energy range at a repetition rate of up to 100 kHz. The maximum average output power at 515 nm was 102 W with pulses of a pulse length of 300 ns. An additional advantage of the presented laser setup is the wide tunability of the pulse duration.

200 kHz electro-optic switch for ultrafast laser systems

A method for obtaining very high electro-optic switching rates is demonstrated and employed for regenerative amplification of ultrashort pulses at high repetition rates. The intracavity polarization switch consists of a transverse-field BBO Pockels cell and a dielectric thin film polarizer. By multiple-shift usage of a single BBO crystal as Pockels cell, it is possible to keep thermal dissipation losses in the Pockels cell driver below 200 W. Using this intracavity polarization switch in an ultrafast thin-disk Yb:KYW regenerative amplifier, pulse energies of about 9 μJ with pulse durations of 280 fs at repetition rates of 200 kHz were generated.

700W intracavity-frequency doubled Yb:YAG thin-disk laser at 100 kHz repetition rate

The thin-disk laser concept with its advantages high efficiency, excellent beam quality, and low depolarization losses provides a reliable platform for the generation of high power lasers in the infrared as well as the green spectral range. By employing intracavity-frequency conversion, we have obtained a maximum output power of 700 W at 515 nm and a repetition rate of 100 kHz from a Q-switched Yb:YAG thin-disk laser. An LBO crystal cut for critical phase matching of type I was mounted near one of the end mirrors inside the laser cavity. An optical efficiency (green output power with respect to incident pumping power) greater than 35% could be reached. By changing the low-loss duration at the Q-switch the pulse duration of the laser system can be adjusted between 200 ns and 750 ns with the longer pulse durations being generated with the highest efficiency. This feature can be used to maintain a constant pulse duration when varying the pumping power or repetition rate. The beam parameter product of 4 mmmrad (M2 < 25) allows for beam delivery via an optical fiber with 100 μm core diameter. To the best of our knowledge, the average power significantly exceeds all previously published results for lasers in the visible spectrum.

Latest advances in high brightness disk lasers

In the last decade diode pumped solid state lasers have become an important tool for many industrial materials processing applications. They combine ease of operation with efficiency, robustness and low cost. This paper will give insight in latest progress in disk laser technology ranging from kW-class CW-Lasers over frequency converted lasers to ultra-short pulsed lasers. The disk laser enables high beam quality at high average power and at high peak power at the same time. The power from a single disk was scaled from 1 kW around the year 2000 up to more than 10 kW nowadays. Recently was demonstrated more than 4 kW of average power from a single disk close to fundamental mode beam quality (M²=1.38). Coupling of multiple disks in a common resonator results in even higher power. As an example we show 20 kW extracted from two disks of a common resonator. The disk also reduces optical nonlinearities making it ideally suited for short and ultrashort pulsed lasers. In a joint project between TRUMPF and IFSW Stuttgart more than 1.3 kW of average power at ps pulse duration and exceptionally good beam quality was recently demonstrated. The extremely low saturated gain makes the disk laser ideal for internal frequency conversion. We show >1 kW average power and >6 kW peak power in multi ms pulsed regime from an internally frequency doubled disk laser emitting at 515 nm (green). Also external frequency conversion can be done efficiently with ns pulses. >500 W of average UV power was demonstrated.

Advanced pulsed thin disk laser sources

Advanced pulsed thin disk laser sources based on several pulse generation schemes, including regenerative amplification as well as cavity-dumping, will be presented. These sources are able to produce pulse energies in the multi-millijoule range at repetition rates of up to several 100 kHz, resulting in average output powers in excess of 100 W. Also the efficient intra-cavity frequency conversion of these sources will be discussed.