The performance of fiber mode-locked lasers is limited due to the high nonlinearity induced by the spatial confinement of the single-mode fiber core.To massively increase the pulse energy of the femtosecond pulses,amp...The performance of fiber mode-locked lasers is limited due to the high nonlinearity induced by the spatial confinement of the single-mode fiber core.To massively increase the pulse energy of the femtosecond pulses,amplification is performed outside the oscillator.Recently,spatiotemporal mode-locking has been proposed as a new path to fiber lasers.However,the beam quality was highly multimode,and the calculated threshold pulse energy(>100 nJ)for nonlinear beam self-cleaning was challenging to realize.We present an approach to reach high energy per pulse directly in the mode-locked multimode fiber oscillator with a near single-mode output beam.Our approach relies on spatial beam self-cleaning via the nonlinear Kerr effect,and we demonstrate a multimode fiber oscillator with M^2<1.13 beam profile,up to 24 nJ energy,and sub-100 fs compressed duration.Nonlinear beam self-cleaning is verified both numerically and experimentally for the first time in a mode-locked multimode laser cavity.The reported approach is further power scalable with larger core sized fibers up to a certain level of modal dispersion and could benefit applications that require high-power ultrashort lasers with commercially available optical fibers.展开更多
文摘The performance of fiber mode-locked lasers is limited due to the high nonlinearity induced by the spatial confinement of the single-mode fiber core.To massively increase the pulse energy of the femtosecond pulses,amplification is performed outside the oscillator.Recently,spatiotemporal mode-locking has been proposed as a new path to fiber lasers.However,the beam quality was highly multimode,and the calculated threshold pulse energy(>100 nJ)for nonlinear beam self-cleaning was challenging to realize.We present an approach to reach high energy per pulse directly in the mode-locked multimode fiber oscillator with a near single-mode output beam.Our approach relies on spatial beam self-cleaning via the nonlinear Kerr effect,and we demonstrate a multimode fiber oscillator with M^2<1.13 beam profile,up to 24 nJ energy,and sub-100 fs compressed duration.Nonlinear beam self-cleaning is verified both numerically and experimentally for the first time in a mode-locked multimode laser cavity.The reported approach is further power scalable with larger core sized fibers up to a certain level of modal dispersion and could benefit applications that require high-power ultrashort lasers with commercially available optical fibers.
