Wolf Seelert

Power scaling of semiconductor laser pumped Praseodymium-lasers

We report on efficient lasing of Pr-doped fluoride materials with cw output powers up to 600 mW in the visible spectral range. Praseodymium doped LiYF(4) and LiLuF(4) crystals were pumped either by an intracavity frequency doubled optically pumped semiconductor laser with output powers up to 1.6 W and nearly diffraction limited beam quality or by a multimode GaN-laser diode with an output power of about 370 mW. Furthermore, intracavity frequency doubling of the red Pr-laser radiation to 320 nm reaching output powers of more than 360 mW with a conversion efficiency of 61% and an optical-to-optical efficiency of 22% are presented.

Semiconductor-laser-pumped high-power upconversion laser

A high-power optically pumped semiconductor laser operating around 970 nm has been used as a pumping source for an upconversion laser based on an Er3+ doped LiLuF4 crystal. Nearly 0.5 W of continuous wave (cw) output power and 0.8 W peak power at a 50% pump duty cycle could be achieved at a wavelength of 552 nm. This represents the highest output power from a room temperature upconversion laser ever reported. Laser threshold and slope efficiency were measured to be below 100 mW of absorbed pump power and 30%, respectively. This experiment could be an important step along the route to realizing a compact and efficient upconversion laser emitting in the Watt level power regime.

Continuous-wave ultraviolet generation at 320 nm by intracavity frequency doubling of red-emitting Praseodymium lasers

We describe a new approach for the generation of coherent ultraviolet radiation. Continuous-wave ultraviolet light at 320 nm has been obtained by intracavity frequency doubling of red-emitting Praseodymium lasers. Lasing at the 640-nm fundamental wavelength in Pr:LiYF(4) and Pr:BaY(2)F(8) was realized by employing an optically pumped semiconductor laser at 480 nm as pump source.Using LiB(3)O(5) as nonlinear medium, ~19 mW of ultraviolet radiation with ~9% optical efficiency with respect to absorbed power was reached for both laser crystals; the visible-to-ultraviolet conversion efficiency was 26% and 35% for Pr:LiYF(4) and Pr:BaY(2)F(8), respectively.

New wavelengths in the yellow-orange range between 545 nm and 580 nm generated by an intracavity frequency-doubled optically pumped semiconductor laser

Diode pumped frequency doubled Optically Pumped Semiconductor lasers (OPS), has proven to be a reliable source of laser radiation in the blue and blue-green spectral range between 460 nm and 505 nm. One of the major advantages of using semiconductors as gain medium is the possibility to tailor the wavelength of the semiconductor material by means of band gap engineering. Here we report about new OPS material enabling the wavelength region between 1090 nm and 1160 nm which allows the realization of frequency doubled lasers between 545 nm and 580 nm. Laser results up to several Watts in the yellow spectral range as well as efficiency and lifetime data will be presented.

UV generation by intracavity frequency doubling of an OPS-pumped Pr:YLF laser with 500 mW of cw power at 360 nm

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.

1 W of 261 nm cw generation in a Pr3+:LiYF4 laser pumped by an optically pumped semiconductor laser at 479 nm

The lack of blue pump sources for Pr-doped materials has been overcome with the recent progress in optically pumped semiconductor lasers (OPS) operating at 479 nm. The availability of reliable high power OPS pump lasers, makes Pr3+-doped crystals ideal gain media for compact and efficient ultraviolet solid-state lasers with output power in the Watt range. We report on the scalability of a 522/261 nm Pr:YLF cw laser that is dual-end-pumped by two OPS lasers at 479 nm. At 9.6 W of incident pump power more than 4 W were obtained at 522 nm with a slope efficiency of 45%. Intracavity frequency doubling of 522 nm resulted in 1 Watt of cw UV output at 261 nm.

Optically pumped semiconductor lasers: a new reliable technique for realizing highly efficient visible lasers

Optically pumped semiconductor material is a complimentary gain medium for rare earth or transition metal doped crystals. The design of several compositions based on GaAs allows the realization of a wavelength range between 710nm and 1180nm. This can be diode pumped and frequency doubled to cover the near UV up to the yellow spectral range. The power is scaleable and we have realized several Watts at 488nm and 460nm. Experimental results will be presented and discussed as well as reliability data to show that this technology has ripened for industrial applications.

1 W 488 nm cw air-cooled optically pumped semiconductor laser

We present an air-cooled optically pumped semiconductor laser that provides a cw output power of 1W at 488 nm. This performance was achieved via intracavity frequency doubling at a laser diode pump power of 2.5 Watts. The increased efficiency was realized by optimizing the OPS chip design and improving the heat extraction from the OPS chip. Efficient cooling of the OPS chip and a compact and mechanically stable folded resonator provide maintenance-free long life laser operation with an M2 of less than 1.1 and a noise of less than 0.25% rms. The size of the laser head is the same as for the 20 mW commercially available version, namely 125 x 70 x 34 mm.

522/261 nm cw generation of Pr:YLF laser pumped by OPS laser

In this paper, we report on 2.5 Watts of output power at 522 nm of Pr:YLF laser end pumped by 5.3 W Coherent High Power OPS Laser at 479 nm, and on 620 mW of cw ultraviolet radiation at 261 nm, which has been obtained by intracavity frequency doubling of the Pr:YLF laser with a BBO crystal.

Ten years optically pumped semiconductor lasers: review, state-of-the-art, and future developments

Optically Pumped Semiconductor Lasers - OPSLs - have been introduced in 2001. Their unique features such as power scalability and wavelength flexibility, their excellent beam parameters, power stability and reliability opened this pioneering technology access to a wide range of applications such as flow cytometry, confocal microscopy, sequencing, medical diagnosis and therapy, semiconductor inspection, graphic arts, forensic, metrology. This talk will introduce the OPSL principles and compare them with ion, diode and standard solid state lasers. It will revue the first 10 years of this exciting technology, its current state and trends. In particular currently accessible wavelengths and power ranges, frequency doubling, ultra-narrow linewidth possibilities will be discussed. A survey of key applications will be given.