Mitigating transverse mode instability in all-fiber laser oscillator and scaling power up to 2.5 kW employing bidirectional-pump scheme.

Transverse mode instability (TMI) is one of the main limiting factors in kW-level fiber lasers. Unlike fiber amplifiers, TMI in fiber laser oscillators attracts less attention from researchers. In this work, we construct an all-fiber ytterbium-doped laser oscillator and investigate the performance in co-pumping and bidirectional-pumping configurations, respectively. In the co-pumping scheme, TMI occurs at ~1.6kW and restricts further output power scaling. Different from the characteristic of dynamic TMI in fiber amplifiers, quasi-static TMI is observed in the laser oscillator. Details of the temporal characteristic around the TMI threshold are provided. In the bidirectional-pumping scheme, experimental results validate that the TMI is mitigated notably by employing bidirectional-pumping instead of co-pumping. The output laser power is further scaled to 2.5kW with a slope efficiency of 74.5% and good beam quality (M2~1.3). At the maximum power, the FWHM bandwidth of optical spectra is 5.2nm, and the Raman stokes light is ~20dB below the signal.

[1]  L. Petit,et al.  Short-Term and Long-Term Stability in Ytterbium-Doped High-Power Fiber Lasers and Amplifiers , 2014, IEEE Journal of Selected Topics in Quantum Electronics.

[2]  Arlee V. Smith,et al.  Mode instability in high power fiber amplifiers. , 2011, Optics express.

[3]  Jesper Lægsgaard,et al.  Static thermo-optic instability in double-pass fiber amplifiers. , 2016, Optics express.

[4]  Cesar Jauregui,et al.  Simplified modelling the mode instability threshold of high power fiber amplifiers in the presence of photodarkening. , 2015, Optics express.

[5]  M. Kanskar,et al.  1-kilowatt CW all-fiber laser oscillator pumped with wavelength-beam-combined diode stacks. , 2012, Optics express.

[6]  Eric Honea,et al.  Threshold power and fiber degradation induced modal instabilities in high-power fiber amplifiers based on large mode area fibers , 2014, Photonics West - Lasers and Applications in Science and Engineering.

[7]  F. Jansen,et al.  Passive mitigation strategies for mode instabilities in high-power fiber laser systems. , 2013, Optics express.

[8]  Pengfei Ma,et al.  Influence of core NA on thermal-induced mode instabilities in high power fiber amplifiers , 2015, 1506.01300.

[9]  Arlee V Smith,et al.  Steady-periodic method for modeling mode instability in fiber amplifiers. , 2013, Optics express.

[10]  T. Eidam,et al.  Experimental observations of the threshold-like onset of mode instabilities in high power fiber amplifiers. , 2011, Optics express.

[11]  Peter Cheng,et al.  1.2-kW single-mode fiber laser based on 100-W high-brightness pump diodes , 2012, Other Conferences.

[12]  M. Zervas,et al.  High Power Fiber Lasers: A Review , 2014, IEEE Journal of Selected Topics in Quantum Electronics.

[13]  Kristian Rymann Hansen,et al.  Theoretical analysis of mode instability in high-power fiber amplifiers. , 2013, Optics express.

[14]  Pu Zhou,et al.  1.5  kW, near-diffraction-limited, high-efficiency, single-end-pumped all-fiber-integrated laser oscillator. , 2014, Applied optics.

[15]  Dapeng Yan,et al.  High power all-fiber amplifier with different seed power injection. , 2016, Optics express.

[16]  Xiangjie Meng,et al.  2.5 kW monolithic continuous wave (CW) near diffraction-limited fiber laser at 1080 nm , 2014 .

[17]  Pu Zhou,et al.  3.15 kW direct diode-pumped near diffraction-limited all-fiber-integrated fiber laser. , 2015, Applied optics.

[18]  John D. Minelly,et al.  3kW single-mode direct diode-pumped fiber laser , 2014, Photonics West - Lasers and Applications in Science and Engineering.

[19]  X. Wang,et al.  Bidirectional pumped high power Raman fiber laser. , 2016, Optics express.

[20]  Hideaki Tobioka,et al.  2.1 kW single mode continuous wave monolithic fiber laser , 2015, Photonics West - Lasers and Applications in Science and Engineering.

[21]  A. Tünnermann,et al.  Narrow linewidth, single mode 3 kW average power from a directly diode pumped ytterbium-doped low NA fiber amplifier. , 2016, Optics express.

[22]  Dietrich Marcuse,et al.  Curvature loss formula for optical fibers , 1976 .

[23]  Andreas Tünnermann,et al.  Build up and decay of mode instability in a high power fiber amplifier. , 2012, Optics express.

[24]  Pengfei Ma,et al.  1.3 kW monolithic linearly polarized single-mode master oscillator power amplifier and strategies for mitigating mode instabilities , 2015 .

[25]  Iyad Dajani,et al.  Modal instability-suppressing, single-frequency photonic crystal fiber amplifier with 811 W output power. , 2014, Optics letters.

[26]  Cesar Jauregui,et al.  Controlling mode instabilities by dynamic mode excitation with an acousto-optic deflector. , 2013, Optics express.

[27]  Cesar Jauregui,et al.  Temporal dynamics of mode instabilities in high-power fiber lasers and amplifiers. , 2012, Optics express.

[28]  Arlee V. Smith,et al.  Influence of pump and seed modulation on the mode instability thresholds of fiber amplifiers. , 2012, Optics express.

[29]  Benjamin Ward,et al.  Theory and modeling of photodarkening-induced quasi static degradation in fiber amplifiers. , 2016, Optics express.

[30]  Pengfei Ma,et al.  1.89 kW all-fiberized and polarization-maintained amplifiers with narrow linewidth and near-diffraction-limited beam quality. , 2016, Optics express.

[31]  B. Ward,et al.  Origin of thermal modal instabilities in large mode area fiber amplifiers. , 2012, Optics express.

[32]  Cesar Jauregui,et al.  High-power fibre lasers , 2013 .

[33]  A. Smith,et al.  Spontaneous Rayleigh Seed for Stimulated Rayleigh Scattering in High Power Fiber Amplifiers , 2013, IEEE Photonics Journal.

[34]  Zejin Liu,et al.  Study of Wavelength Dependence of Mode Instability Based on a Semi-Analytical Model , 2015, IEEE Journal of Quantum Electronics.

[35]  Zejin Liu,et al.  Mitigating of modal instabilities in linearly-polarized fiber amplifiers by shifting pump wavelength , 2014, 1412.0965.

[36]  Arlee V. Smith,et al.  Increasing mode instability thresholds of fiber amplifiers by gain saturation. , 2013, Optics express.

[37]  K. Hejaz,et al.  Controlling mode instability in a 500 W ytterbium-doped fiber laser , 2014 .

[38]  Daiichiro Tanaka,et al.  2 kW single-mode fiber laser with 20-m long delivery fiber and high SRS suppression , 2016, LASE.