Suppression of parasitic lasing and inter-pulse self-pulsing in a pulsed Erbium–Ytterbium co-doped fiber amplifier

• Published in: Applied physics. B, Lasers and optics Vol. 126; no. 1
• Main Authors: Agrawal, Lalita, Ganotra, Dinesh
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 2020; Springer Nature B.V
• Subjects: Applied physics; Bandpass filters; Broadband; Configuration management; Configurations; Doped fibers; Engineering; Erbium; Fiber lasers; Lasers; Lasing; Optical Devices; Optics; Photonics; Physical Chemistry; Physics; Physics and Astronomy; Power amplifiers; Preamplifiers; Pulse duration; Quantum Optics; Relaxation oscillations; Rollover; Semiconductor lasers; Signal quality; Spectra; Spontaneous emission; Ytterbium
• ISSN: 0946-2171; 1432-0649
• DOI: 10.1007/s00340-019-7368-8

Performance of an Erbium–Ytterbium co-doped fiber (Nufern PM EYDF 12/130) has been investigated as a power amplifier stage for developing a pulsed, high peak power, 1550 nm laser with 30 ns pulse duration at 10 kHz repetition rate. A directly modulated, broadband, Fabry–Perot laser diode has been employed as seed laser in all fiber master oscillator power amplifier (MOPA) configuration. Amplifier performance was significantly improved by improving the spectral quality of seed and preamplifiers using two band-pass filters in tandem. This may be attributed to the reduction in inter-pulse Amplified Spontaneous Emission (ASE) noise. Comparative results have been presented for two different MOPA configurations. MOPA with broader signal spectrum resulted in Yb parasitic lasing at 5 W pump power causing roll over in the output energy. Also, onset of strong self-pulsing was observed during off period (in absence of signal pulse) at ~ 6.3 W input. Nature of these pulses resembled relaxation oscillations. Theoretically calculated time period (10–12 µs) of the self-pulses at various pump powers matched fairly well with the experimental results. However, with improved signal spectral quality, no such inter-pulse self-pulsing and parasitic lasing was observed up to 12 W pump power. More than 75 µJ energy per pulse was achieved, limited by power-handling capability of the output isolator. We present here several novel experimental results in terms of spectral, temporal and energy output for a pulsed EYDF amplifier generating 2.5 kW pulses @ 1550 nm.