Pulse dynamics in mode-locked lasers: relaxation oscillations and frequency pulling

Curtis R Menyuk,Jared K Wahlstrand,John Willits,Steven T Cundiff,Ryan P Smith,Thomas R Schibli

doi:10.1364/oe.15.006677

Abstract

A theoretical description of the pulse dynamics in a modelocked laser including gain dynamics is developed. Relaxation oscillations and frequency pulling are predicted that influence the pulse parameters. Experimental observations of the response of a mode-locked Ti:sapphire laser to an abrupt change in the pump power confirm that the predicted behavior occurs. These results provide a framework for understanding the effects of noise on the spectrum of the laser.

Highlights

Remarkable advances in the ability to measure and control the phase evolution of the pulses produced by mode-locked lasers have occurred over the last few years [1]
Efforts to describe the dynamics of a mode-locked laser have been based on an approach described in a seminal paper by Haus and Mecozzi [13]
We have experimentally measured some elements in the matrix A that describes the dynamics of the pulse parameters in a Ti:sapphire mode-locked laser

Summary

Introduction

Remarkable advances in the ability to measure and control the phase evolution of the pulses produced by mode-locked lasers have occurred over the last few years [1]. There are contributions from changes in the center frequency [6, 8], which depends on the intensity through frequency pulling, contributions from changes in the pulse timing due to shock [9], and modification due to dispersion management in the laser [10] These studies did not develop an understanding of the dynamical aspects of these effects, while experimental results only distinguished slow thermal effects from faster non-thermal ones [8]. An accurate theoretical description of the pulse dynamics will aid efforts to improve the feedback control of mode-locked lasers because the dynamics become part of the transfer function of the servo loop Such a theoretical description will allow the effect of noise on the frequency comb to be analyzed. Experimental characterization of the dynamics show that the dynamics of the gain medium must be included

Background

Experiment

Frequency pulling

Conclusion