There are two main design concerns for making a femtosecond, mode-locked oscillator (and many smaller ones):

• The cavity needs a saturable absorber to support pulse formation and suppress continuous-wave lasing
• The cavity needs to support perfectly periodic pulse evolutions (e.g., but not limited to, solitons)

Recently, the Mamyshev mechanism has been shown to act as a super-strong saturable absorber. This enables not only new power levels, but new types of pulse evolutions in fiber oscillators. The big problem with these lasers is the saturable absorber is so strong that they typically require seed pulses from a separate mode-locked laser to start.

I designed a Mamyshev oscillator that largely solves this problem, and is able to self-start without an additional laser. The laser is also exceptionally easy to construct. The cavity is very carefully designed to feature a type of pulse evolution that relies on a nonlinear attractor based on a complex interplay between shifting inversion levels in Yb-doped gain fiber and parabolic (self-similar-like) pulse shaping.

The end result is an all-fiber-integrated laser smaller than a shoebox, which is dead-simple to construct, and makes 40 fs pulses that reach over 1 MW peak power. This is over 20 x higher than any previous all-fiber, self-starting oscillator. Read about it here.