Abstract
Active phase locking of a multicore erbium-doped fiber amplifier is demonstrated for 180 ns narrow-linewidth pulses at 1545 nm. A spatial light modulator is used at the input of the amplifier to control the optical phase of 7 beams injected in the hexagonally-arranged cores, ensuring efficient combining through a SPGD algorithm. At the output, combining is performed using a diffractive optical element. This experiment establishes multicore amplifiers as a promising way to scale the energy of Brillouin-limited pulsed amplifiers for LIDAR applications. We also present a simple lensless technique to measure phase shifts between pairs of adjacent channels that could be implemented in future active coherent combining systems.
Highlights
Power scaling of fiber-based laser sources has shown tremendous progress over last decades
Active phase locking of a multicore erbium-doped fiber amplifier is demonstrated for 180 ns narrow-linewidth pulses at 1545 nm
A spatial light modulator is used at the input of the amplifier to control the optical phase of 7 beams injected in the hexagonally-arranged cores, ensuring efficient combining through a SPGD algorithm
Summary
Power scaling of fiber-based laser sources has shown tremendous progress over last decades. Applications require ever-increasing performances, in various temporal regimes An example of such application is Doppler LIDAR, where long (~100 ns) energetic (~100 μJ - 1 mJ) narrow-linewidth pulses are used to probe wind speed [1] in the atmosphere. In this regime, Brillouin scattering limits the peak power at the output of large mode area fiber amplifiers to around 1 kW [2]. Coherent Beam Combining (CBC) is widely recognized as a way to scale the power and energy of laser sources while retaining the spatial and temporal properties of a single source. This work is a promising step towards multi-kW peak power systems for Doppler LIDAR applications
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