Abstract
We report an Yb-doped fiber master-oscillator power-amplifier (MOPA) system with the capability of selectively generating doughnut-shaped radially and azimuthally polarized beams with user-defined temporal pulse shapes. The desired output polarization was generated with the aid of a nanograting spatially variant half-waveplate (S-waveplate). The latter was used to convert the linearly polarized fundamental (LP01) mode output from the preamplification stages to a doughnut-shaped radially polarized beam prior to the power amplifier stage. A maximum output pulse energy of ∼860 μJ was achieved for ∼100 ns pulses at 25 kHz with user-defined pulse shape for both radial and azimuthal polarization states. The polarization purity and beam propagation factor (M2) were measured to be >12 dB and 2.2, respectively.
Highlights
Since the vector TM01 and TE01 modes in circular core fibers have radial and azimuthal polarization states, respectively, it is possible to generate these unique beams from a fiber master-oscillator poweramplifier (MOPA) system while maintaining the capability of controlling the temporal pulse shape to benefit materials processing
In this Letter, for the first time to the best of our knowledge, we present an Yb-doped fiber (YDF) MOPA system for efficiently generating high-energy radially and azimuthally polarized nanosecond pulses
The spatial mode shaping is achieved by using an S-waveplate to convert the linearly polarized fundamental (LP01) mode from the preamplification stages into a doughnut-shaped radially polarized beam prior to the power amplifier
Summary
Since the vector TM01 and TE01 modes in circular core fibers have radial and azimuthal polarization states, respectively, it is possible to generate these unique beams from a fiber MOPA system while maintaining the capability of controlling the temporal pulse shape to benefit materials processing. In this Letter, for the first time to the best of our knowledge, we present an Yb-doped fiber (YDF) MOPA system for efficiently generating high-energy radially and azimuthally polarized nanosecond pulses.
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