Analysis of Self-Starting Harmonic Mode-Locking in an Electro-Optic-Feedback Laser

The concept of the self-starting harmonic mode-locking (SSHML) by electro-optical feedback in a solid-state laser is studied. Such an operational mode with m equidistant pulses in a laser cavity is controlled by a delayed single negative electro-optical feedback loop which comprises an intracavity electro-optical modulator and a fast high-voltage photodiode mounted directly on it. Analytical expressions for the feedback delay time and the short pulse duration are derived depending on laser parameters. The build-up time of the SSHML process and the limiting gain values are assessed by a high-resolution numerical simulation. For the purposes of accelerator physics, the pulse duration estimations for a set of the widely used Nd and Yb active media are provided. Robustness, high limiting gain and low sensitivity to gain level make SSHML laser an attractive platform for future multi-bunch photoinjector design.