Reduction of timing jitter and intensity noise in normal-dispersion passively mode-locked fiber lasers by narrow band-pass filtering.

Peng Qin,Hyoji Kim,Youjian Song,Minglie Hu,Junho Shin,Dohyeon Kwon,Jungwon Kim,Chingyue Wang

doi:10.1364/oe.22.028276

Peng Qin, Hyoji Kim + Show 6 more

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https://doi.org/10.1364/oe.22.028276

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Abstract

Fiber lasers mode-locked with normal cavity dispersion have recently attracted great attention due to large output pulse energy and femtosecond pulse duration. Here we accurately characterized the timing jitter of normal-dispersion fiber lasers using a balanced cross-correlation method. The timing jitter characterization experiments show that the timing jitter of normal-dispersion mode-locked fiber lasers can be significantly reduced by using narrow band-pass filtering (e.g., 7-nm bandwidth filtering in this work). We further identify that the timing jitter of the fiber laser is confined in a limited range, which is almost independent of cavity dispersion map due to the amplifier-similariton formation by insertion of the narrow bandpass filter. The lowest observed timing jitter reaches 0.57 fs (rms) integrated from 10 kHz to 10 MHz Fourier frequency. The rms relative intensity noise (RIN) is also reduced from 0.37% to 0.02% (integrated from 1 kHz to 5 MHz Fourier frequency) by the insertion of narrow band-pass filter.

Highlights

Mode-locked lasers can generate optical pulse trains with extremely low timing jitter down to the attoseconds level, as predicted by laser noise theory [1,2]
The direct output pulse duration will decrease with cavity dispersion in the absence of narrow band-pass filtering
Several mode-locking conditions are investigated in terms of cavity dispersion map and narrow band-pass filtering

Summary

Introduction

Mode-locked lasers can generate optical pulse trains with extremely low timing jitter down to the attoseconds level, as predicted by laser noise theory [1,2]. All experimental demonstrations of timing jitter reduction in fiber lasers have required a careful optimization of cavity dispersion towards zero [11,12], where the pulse train is immune to the Gordon-Haus jitter [13]. Fiber lasers operating at normal dispersion is proved to have much larger jitter due to the larger Gordon-Haus jitter as has been experimentally characterized in [8] It has been shown both theoretically [1,2] and experimentally [22,23] that intra-cavity filtering can act as a restoring force to reduce Gordon-Haus jitter in passively mode-locked lasers. It has been predicted that a narrow bandpass filter can make the jitter independent of cavity dispersion map due to amplifier-similariton formation [24]

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Conclusion