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Pump modulated suppression of self pulsing in a pulsed fibre amplifier
Published in SPIE
2018
Volume: 10683
   
Abstract
We present an experimental study on the suppression of self pulsing in a single stage pulsed master oscillator power amplifier (MOPA), using pump modulation. Many applications require pulsed lasers operating at low repetition rate. Leaving the pump on for long duration without a seed pulse leads to accumulation of amplified spontaneous emission (ASE) and generation of a self-pulse that can damage the laser. For this experiment, the amplifier was fed with peak seed power of 500 mW having a pulse width and repetition rate of 100 ns and 10 kHz respectively. To study the effect of pump modulation on self-pulsing, we carried out the experiment with both a continuous pump and with a pulsed pump. The output was characterized using a constant fractional discriminator (CFD) that generated TTL pulses, in turn fed to a frequency counter. In case of a continuous pump of 2.4 W, with a low repetition rate of 10 kHz for the seed, we noticed self-pulsing of the MOPA. We obtained a maximum amplified signal output peak power of 162 W, or a pulse energy of 7.91 μJ. A further increase in pump power could lead to permanent damage to the system. In case of pulsed pump, the generated pump pulses were synchronized with the seed laser and had a 50 % duty cycle. The resulting output was again characterized with a CFD and counter. We were able to increase the pump power to 6.5 W with an output peak power of 160 W and pulse energy of 9.37 μJ without any sign of self-pulsing. Thus, using a simple method of pump modulation, we were able to reduce the accumulation of ASE and suppressed the phenomenon of self-pulsing at low repetition rates of the seed laser. © 2018 SPIE.
About the journal
JournalData powered by TypesetProceedings of SPIE - The International Society for Optical Engineering
PublisherData powered by TypesetSPIE
ISSN0277786X
Open AccessNo
Concepts (16)
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    Fiber amplifiers
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    Fiber lasers
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    Fibers
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    Glass
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    Modulation
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    OPTICAL PHASE CONJUGATION
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    Power amplifiers
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    Pulse repetition rate
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    Pulsed lasers
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    Spontaneous emission
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    AMPLIFIED SPONTANEOUS EMISSIONS
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    GAIN MODULATION
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    MASTER OSCILLATOR POWER AMPLIFIERS
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    PUMP MODULATION
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    SELF-PULSING
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    Optical pumping