LIEKKI Introduces Optimized Polarization Maintaining Fiber for High-Energy Amplification

Lohja, Finland  August 15, 2006

LIEKKI, the leading supplier of highly doped optical fibers, has developed an ideal polarization maintaining fiber for amplifying pulses from 1 μm lasers.

LIEKKI expands its broad, ytterbium-doped fiber product family with a highly doped, large mode area fiber with very high cladding absorption (LIEKKI™ Yb1200-20/125DC-PM). Typical applications of this fiber are materials processing (cutting, marking, drilling), laser ranging, remote chemical detection, and nonlinear frequency conversion for access to wavelengths from the infrared to the ultraviolet. These applications require pulsed amplifiers with mJ output energies, diffraction-limited beam quality and single polarizations, specifications that have previously been unattainable with fiber-based laser systems. Development of a fiber with a large mode area and short active fiber length provided the breakthrough required to minimize nonlinear effects, the key limitation on the achievable output energy from conventional fiber amplifiers. “Overcoming this limitation will substantially increase the range of applications that can be addressed by fiber lasers,” says Mr. Mikko Söderlund, Product Manager of LIEKKI’s fiber products.

“This highly doped ytterbium fiber with its extremely high pump absorption, high power conversion efficiency, polarization preservation and large mode area is excellent for amplification of pulses with durations ranging from nanoseconds to femtoseconds. Such high-power pulses are typically used in material processing and micromachining”, continues Mr. Söderlund. The LIEKKI™ Yb1200-20/125DC-PM fiber features a unique combination of a highly doped, 20 μm diameter core and a large core-to-cladding ratio. These features result in a nominal cladding pump absorption of 7.1 dB/m at 920 nm rising to as much as 30 dB/m for absorption near the peak at around 976 nm, enabling use of very short active fiber lengths (less than a meter for 976 nm pumping). Applications using this fiber benefit from high extractable energy and excellent beam quality. The use of standard 125 μm cladding diameter is another advantage, broadening the fiber’s usability, for example, with standard telecom fiber stripping, splicing, and connectorization equipment.

LIEKKI supplies a passive fiber matched to the active ytterbium fiber, so that excellent beam quality is maintained throughout the monolithic fiber laser or amplifier assembly. Combiners, such as 6+1/1 based on tapered fiber bundle technology, and endcaps are also available through LIEKKI. “This approach is part of our mission to provide complete solutions to our customers”, concludes Mr. William Willson, LIEKKI's Vice President Marketing and Sales.

Fig. 1: Cladding absorption of LIEKKI’s Yb1200-20/125DC-PM fiber

Fig. 2: Typical power conversion efficiency of LIEKKI’s Yb1200-20/125DC-PM fiber