Fiber MOPAs in the infrared wavelength region offer the advantage of high single mode output powers, independent
selection of pulse repetition rates and pulse durations, and access to high repetition rates. Despite these performance
advantages, most industrial and scientific applications in the visible and the ultraviolet spectral range are still dominated
by solid state lasers. We will give an overview of the technical challenges of harmonic generation in fiber lasers and
fiber amplifiers and discuss the state-of-the-art and future of Fiber MOPAs and bulk solid state lasers with harmonic
Quasi-cw UV light sources are of interest for replacing frequency-doubled Ar-Ion lasers in several applications. Our
target application in semiconductor inspection requires a narrow bandwidth cw or quasi-cw source at 258nm, which
cannot be achieved by frequency converting the output of a (modelocked) Neodymium-based laser.
We developed a fiber MOPA system which operates at a high repetition rate of 5MHz and generates 1ns long pulses.
The system consists of a low power oscillator and four consecutive amplifier stages. which boost the average power to
40W at 1031nm.
The IR output of the fiber system is frequency doubled and quadrupled using LBO and CLBO crystals for SHG and
FHG, respectively. We achieved SHG conversion efficiencies of up to 82% and a UV power of up to 14W.
We report on a hybrid fiber MOPA + solid-state amplifier for frequency conversion and compare a hybrid
scheme versus all- fiber MOPA. Using a thoroughly designed master oscillator and optimized fiber amplifiers we were
able to achieve 15-30ns long pulses at average powers above 20 W with a good spectral quality and suppressed SBS.
Bulk Vanadate amplifiers boosted the 1064nm output power to greater 65W at pulse repetition rates of 300-500 kHz.
More than 35 W in green and 20 W of UV light has been obtained at pulse repetition rates above 300 kHz and pulse
energies of 30-100 μJ.
We report a simple, environmentally-stable, passively mode-locked Yb-based fiber oscillator operating at 1035 nm with pulse duration of ~5 ps. Mode-locking was achieved using a saturable absorber mirror. The output of the laser exhibited a polarization extinction ratio >20 dB with the implementation a polarization maintaining fiber cavity and a polarization sensitive fiber coupler. The laser outputted near transform-limited pulses at 25-100 MHz at a pump threshold of 20-30
mW. We have tested operation of the laser using two different saturable absorber mirror structures: multiple quantum wells and quantum-dots at 1035 nm. Pulse properties and laser performance were comparable using quantum-dots and multiple quantum wells as the saturable absorber.