The development of kW-class diode-pumped picosecond laser sources emitting at various wavelengths started at the HiLASE Center four years ago. A 500-W Perla C thin-disk laser with a diffraction limited beam and repetition rate of 50–100 kHz, a frequency conversion to mid-infrared (mid-IR), and second to fifth harmonic frequencies was demonstrated. We present an updated review on the progress in the development of compact picosecond and femtosecond high average power radiation sources covering the ultraviolet (UV) to mid-IR spectral range at the HiLASE Center. We also report on thin-disk manufacturing by atomic diffusion bonding, which is a crucial technology for future high-power laser development.

We report new observations on picosecond deep ultraviolet coherent beams generated in a CLBO as the fourth and fifth harmonics of a diode pumped high average power Yb:YAG thin disk laser operating at 77 kHz repetition rate at 1030 nm. The effects of the two-photon absorption were observed, e.g. the modification of phase matching conditions, lowering of the conversion efficiency. The fifth harmonic generation (4ω+1ω) was studied for different time delays between both pump beams and for the case of excess input power of the fundamental. The latter effect suggests a possibility of increasing DUV output at short crystals. The highest output power obtained at 257 nm was 7.6 W and 1 W at 206 nm. To our knowledge these DUV output powers rank among the highest for picosecond pulses at the repetition rate of the order of magnitude of 100 kHz.

In this paper, we present the stability characteristics of a supercontinuum (SC) generated in a 60 mm, 100 mm, and 130 mm long undoped yttrium aluminum garnet (YAG) crystal pumped by a Yb thin-disk regenerative amplifier. The 1.2 ps pulses with a central wavelength of 1030 nm and repetition rate of 89 kHz are loosely focused (NA = 0.0031) into the crystal in order to prevent laser-induced damage and to increase the energy stability of the generated SC. Out of the tested crystal lengths, the optimal is experimentally determined to be 130 mm. The energy contained in the blueshifted side, which has a 530 nm spectral cutoff, is 71 nJ and exhibits average power stability of 0.4% RMS, which is 2.5× better than the stability of the pump beam.

We report on the generation of picosecond pulses at 515 nm and deep ultraviolet pulses at 257 nm and 206 nm. They are generated as second, fourth and fifth harmonic frequencies of the high power diode-pumped Yb:YAG thin-disk laser at the fundamental wavelength of 1030 nm. The laser at the fundamental wavelength is based on a chirped-pulse amplification of oscillator pulses in two-stage regenerative amplifier based on thin-disks as active media. The diode pumping at the zero phonon line is used. The pulses are produced at ~100 kHz repetition frequency, 2-10 ps pulse duration and ≤2 mJ pulse energy. The fundamental beam is doubled in an LBO crystal at an efficiency of 42%. Subsequently the fourth harmonic frequency (257 nm) is produced by frequency doubling of the second harmonic frequency in a CLBO crystal. The unconverted part of the fundamental beam after SHG is used with the fourth harmonic beam as 1ω+4ω frequency sum in a further CLBO crystal for the fifth harmonic frequency (206 nm) generation. Two issues are important in the efficient optical conversion: nonlinear absorption given mainly by two-photon absorption (TPA) and proper timing of interacting pulses. In our simulations we take into account TPA and study the consequences of different timing of 1ω- and 4ω-pulses on the CLBO when generating the 5th harmonic. It was found that 1.4 ps delay of the 1ω-pulse after the 4ω-pulse is necessary to get the highest 5ω-output. Also the 5ω-pulse duration is affected by the timing.

The usage of coherent radiation in the mid-infrared (mid-IR) wavelength range (2 – 8 μm) covers a wide spectrum of applications in many different fields. To satisfy the demand for a high-power, picosecond mid-IR source, we are developing an optical parametric system tunable between 1.45 and 3.5 μm in wavelength. The pumping of the system is provided by an in-house built Yb:YAG thin-disk laser, delivering 80 W of average power at 93 kHz pulse repetition rate, 1030 nm wavelength and ~1.3 ps pulse duration. The optical parametric system consists of a double-pass optical parametric generator (OPG) based on a periodically poled lithium niobate. By utilizing four periods of poling and temperature tuning, wavelength tunability range is from 1.45 to 3.5 μm. Maximum signal output power was around 85 mW at 1850 nm wavelength at 2 W pump power. Subsequent amplification of the signal generated in the OPG stage takes place in an optical parametric amplifier (OPA), which consists of a pair of walk-off compensating KTA crystals, pumped by up to 50 W average power. Maximum output signal and idler sum power after the OPA stage was 8.4 W. The wavelength tunability of the amplifier spans from 1.5 to 3.2 μm. Further increase in the tunability range as well as gapfree tuning is currently crystal mount-limited.

Increase in energy of ultrashort (picosecond, femtosecond) laser pulses is typically based on chirped pulse amplification (CPA) method. The nanojoule energy pulses are temporally stretched by several orders of magnitude prior amplification. The peak power is significantly decreased and the gain s...