A study of a higher order FM mode‐locking laser with double phase modulators

Abstract

AbstractGenerating high‐repetition‐rate short pulses from higher order FM mode‐locked lasers requires many sidebands. However, in reality, the physical limit of modulators makes it impossible to increase the modulation index. This paper proposes a novel higher order FM mode‐locked laser that has two PM‐I‐FP sets (phase modulator, isolator, and Fabry‐Perot filter) and presents an analysis of its performance. The laser uses a new technique that makes the value of the synthesized transfer function of a PM‐I‐FP equal in both the 0 and π phase states. This technique improves the frequency characteristics of the modulator substantially. As a result, the maximum repetition rate is doubled, and the laser also generates a chirp‐free and narrower pulse train with uniform amplitude and pulse width. We also propose a system that has only one PM‐I‐FP. This eliminates problems that arise due to differences in the PM‐I‐FP characteristics when two PM‐I‐FP sets are used. The same effects as mentioned above are achieved. © 2003 Wiley Periodicals, Inc. Electron Comm Jpn Pt 2, 86(3): 1–10, 2003; Published online in Wiley InterScience (www.interscience. wiley.com). DOI 10.1002/ecjb.10083