We report on detailed spectroscopic investigations and efficient visible upconversion laser operation of Er3+:LiLuF4. This material allows for efficient resonant excited-state-absorption (ESA) pumping at 974 nm. Under spectroscopic conditions without external feedback, ESA at the laser wavelength of 552 nm prevails stimulated emission. Under lasing conditions in a resonant cavity, the high intracavity photon density bleaches the ESA at 552 nm, allowing for efficient cw laser operation.We obtained the highest output power of any room-temperature crystalline upconversion laser. The laser achieves a cw output power of 774 mW at a slope efficiency of 19% with respect to the incident pump power delivered by an optically-pumped semiconductor laser. The absorption efficiency of the pump radiation is estimated to be below 50%.To exploit the high confinement in waveguides for this laser, we employed femtosecond-laser pulses to inscribe a cladding of parallel tracks of modified material into Er3+:LiLuF4 crystals. The core material allows for low-loss waveguiding at pump and laser wavelengths. Under Ti:sapphire pumping at 974 nm, the first crystalline upconversion waveguide laser has been realized. We obtained waveguide-laser operation with up to 10 mW of output power at 553 nm. (C) 2015 Elsevier B.V. All rights reserved.

Excitation mechanisms and requirements on materials, and pump sources for crystalline up-conversion lasers will be discussed. Using suitable pump- and resonator arrangements significant improvement of existing results concerning room temperature up-conversion lasers could be achieved.

The dynamic behavior of the continuous wave output of an intracavity frequency doubled optically pumped semiconductor disk laser is described. These lasers typically exhibit stable emission. The reasons are found to be the tendency to single-mode operation and the high gain coupling of different modes due to an extremely short gain medium and the resonant periodic gain structure. A dependence of the fluctuation amplitude on gain decoupling of different fundamental modes is demonstrated. With the presented laser setup, more than 80% of conversion efficiency with respect to the available fundamental power has been achieved.

We present an efficient in-band-pumped Er(0.2 at%):Sc(2)O(3)-laser at 1581 nm with a maximum output power of 0.95 W and a maximum slope efficiency of 31%. (C) 2008 Optical Society of America

In this paper, we report on 500 mW of cw ultraviolet radiation at 360 nm, which has been obtained by intracavity frequency doubling of a Pr:YLF laser, end pumped by 1.8 W Coherent High Power OPS Laser at 479 nm. We have demonstrated the scalability of Pr:YLF laser to pump power of 5.3Watts, resulting in real continuous wave 2.5 Watts of output power at 720 nm and cw 1.3 Watts at 360 nm.

We review spectroscopic properties, basic laser parameters, and efficient lasing of Pr-doped fluoride materials. Continuous output powers up to 600 mW in the visible spectral range as well as intracavity frequency doubling to the UV spectral region under semiconductor laser pumping is reported. We achieved powers of 600 mW in the visible spectral region and 360 mW of UV radiation corresponding to a conversion efficiency of 61% with an optical-to-optical efficiency of 22%.

Using an optically pumped semiconductor laser as pumping source nearly 0.5 W cw and 0.8 W maximum output at 50% pump duty cycle are achieved from a room temperature Er 3+ :LiLuF 4 upconversion laser at 552 nm.

A 1.5 µm-Er,Yb:glass laser endpumped by a 3.7 W laser diode at a wavelength of 975 nm was investigated in continuous wave as well as in active Q-switch operation. The experimental results have been compared to a laser simulation based on a model of rate equations.