Abstract
We experimentally investigate the noise properties of a homemade 586 MHz mode-locked laser (MLL). The variation of the timing jitter versus the harmonic order is measured, which is consistent with the theoretical analyses. The dominant contributions to the timing jitter are detailedly studied by analyzing the phase noises at different harmonic frequencies. For low-order harmonics, the intensity noise and relative-intensity-noise-coupled (RIN-coupled) jitter mainly contribute to the timing jitter, while for high-order harmonics, the amplified spontaneous emission (ASE) noise makes the dominant contribution. Then we find that a higher output ratio has an obvious improvement on reducing the timing jitter and suppressing the phase noise because of the shorter pulse duration and lower net cavity dispersion caused by the higher output ratio. Finally a comparison of the noise performance between the MLL and a commercial signal generator is made, which shows that the optically generated radio-frequency signal (OGRFS) has a lower phase noise at high offset frequencies, however the higher phase noise at low offset frequencies leads to a higher timing jitter than the commercial SG.
Highlights
In recent years, passively mode-locked fiber lasers (MLLs) have rapidly developed and been widely used in many application fields, such as optical frequency comb generation [1], [2], high-resolution optical sampling [3], precision optical metrology [4], low noise microwave signal extraction [5], [6], photonics-based radar system [7], and so on
The influence of the output ratio of the MLL on timing jitter is studied in Section 4, the results show that a higher output ratio assists in reducing the timing jitter and suppressing the phase noise by narrowing the pulse duration and decreasing the net cavity dispersion
We find that the measured timing jitter decreases with the increasing harmonic order at first and remains constant with a ±20 fs fluctuation
Summary
Passively mode-locked fiber lasers (MLLs) have rapidly developed and been widely used in many application fields, such as optical frequency comb generation [1], [2], high-resolution optical sampling [3], precision optical metrology [4], low noise microwave signal extraction [5], [6], photonics-based radar system [7], and so on In these systems, the noise property should be improved as much as possible in order to assure the required system performance in terms of sensitivity and precision. No detailed study on timing jitter and phase noise at different harmonics of a passively MLL has been done so far as we know, which is important in generating low noise high frequency microwave signal from a MLL and some other applications.
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