Gain Saturation and Output Characteristics of Index-Antiguided Planar Waveguide Amplifiers With Homogeneous Broadening

We investigate numerically and analytically the propagation characteristics of gain-guided modes in index-antiguided planar waveguides. We show that the gain-guided mode has modal confinement proportional to the modal gain, and single-transverse mode propagation is very robust in such waveguides. The power evolution of the fundamental mode can be described analytically with very good accuracy. Limiting power and optimum length of the waveguide amplifiers can also be obtained analytically.