Mamyshev fiber oscillators: environmental stability and record performance (Conference Presentation)

Abstract

Ultrafast fiber lasers could provide a compact, robust and cheaper alternative to solid-state sources, such as Ti:sapphire oscillators. If fiber sources can provide equal performance at a fraction of the cost, then many applications of ultrafast pulses and frequency combs will be poised for explosive adaption beyond research laboratories. For the past decade, a major impediment to this has been the reliance on nonlinear polarization rotation (NPR) to mode-lock the lasers. Without NPR, performance is usually insufficient. With NPR, the laser is environmentally unstable. In the past year, remarkable developments have been made based on the use of the Mamyshev regenerator, which simply combines the power-dependent spectral broadening of self-phase modulation with offset spectral filtering to achieve power-dependent transmission. A gain fiber is used to compensate for filtering losses. By arranging two Mamyshev regenerators with opposing spectral filter offsets in a loop, we created a Mamyshev oscillator. Polarization maintaining fibers are used for environmental stability. The power-dependent transmission means that continuous wave lasing is suppressed, and only pulsed operation is possible. This simple but significant change means that incredibly large nonlinear phase shifts can be tolerated. We leverage this large nonlinearity to create spectral bandwidth in a parabolic pulse. We find that the Mamyshev oscillator provides an order-of-magnitude better performance – 1 MW from standard single-mode fiber - than any previous design. Simulations suggest that still greater performance is achievable, and experiments in our laboratory show promise to 10 MW and beyond. Finally, self-starting Mamyshev oscillator results will be discussed.