Fiber laser system produces record power

Oct. 1, 2000
Scientists at the Institute for Applied Physics of the Friedrich Schiller University (Jena, Germany) and the Max Born Institute (Berlin, Germany) have demonstrated a powerful sub-picosecond fiberoptic laser system at a wavelength of 1.06 µm.

Scientists at the Institute for Applied Physics of the Friedrich Schiller University (Jena, Germany) and the Max Born Institute (Berlin, Germany) have demonstrated a powerful sub-picosecond fiberoptic laser system at a wavelength of 1.06 µm. The system, which is based on chirped pulse amplification (CPA) in double-clad fibers and pulse compression, achieved 10-µJ pulses at a repetition rate of 2 MHz using a multimode fiber as the amplifier. Output was 22 W with a reasonable beam quality (m2 approaching 7). With a monomode amplifying fiber, the laser produced 100-µJ pulses at a 32 kHz repetition rate in a nearly diffraction-limited beam (m2 near 1.6).

According to Professor Andreas Tünnermann and colleagues at the Institute for Applied Physics, the modelocked oscillator of the laser system supplies 150-fs, 1.2-nJ pulses at an 82-MHz repetition rate (see figure). An acousto-optic modulator selects every 40th pulse to be fed into a pulse stretcher made of a 2-km standard single-mode fiber. A chain of two neodymium-doped preamplifiers and two ytterbium-doped amplifiers, cladding pumped by fiber-coupled laser diodes, yields the output that is fed to the grating compressor. A second acousto-optic modulator allows the selection of a repetition rate between 32 kHz and 2 MHz to yield the output specified above.

Slope efficiency of the multimode fiber amplifier is 52% (optical to optical). The pulse width is 710 fs, full-width half-maximum. With a pulse energy of 100 µJ, the peak power reaches 140 MW.

The researchers believe the diode-pumped solid-state device, with its unprecedented power and considerably higher frequency than Ti:sapphire CPA systems, has possible applications in micromachining and extreme-ultraviolet generation. Further development of the system may also someday lead to reliable high-power lasers that can be tailored for emission at visible wavelengths such as red, green, and blue for display purposes. For more information, contact Tünnermann at [email protected].

About the Author

Uwe Brinkmann | Contributing Editor, Germany

Uwe Brinkmann was Contributing Editor, Germany, for Laser Focus World.

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