Abstract
Highly coherent and low-noise supercontinuum (SC) sources based on nonlinear spectral broadening of femtosecond pulses in all-normal dispersion (ANDi) fibers are attractive for many applications in ultrafast photonics. By simulating a real nonlinear pulse compression experiment, we numerically investigate the impact of shot noise and technical pump laser fluctuations on the quality and stability of single-cycle pulse generation and other multi-shot experiments based on the manipulation of the SC spectral phase. We find that for pump pulse durations of less than 600 fs, input relative intensity noise < 1 %, and correctly chosen fiber lengths, the initial fluctuations of the pump laser are at most amplified by a factor of three. We also show that the usual strong correlation between SC coherence and quality of the compressed pulses collapses in the presence of technical noise, and that in this situation the coherence is not a useful figure of merit to quantify pulse quality, noise amplification, or decoherence due to incoherent nonlinear dynamics. Our results highlight the very limited impact of technical pump laser noise on ANDi SC generation and are of practical relevance for many ultrafast photonics applications that require high-quality, low-noise SC sources.
Highlights
The nonlinear spectral broadening of femtosecond pulses in all-normal dispersion (ANDi) fibers has emerged as an attractive way of realizing low-noise, highly coherent, and octave-spanning supercontinuum (SC) sources [1]
While it was found that the ANDi SC generation dynamics do not significantly amplify technical noise and that the relative intensity noise (RIN) of the SC in the central part of the spectrum can be lower than the RIN of the mode-locked pump laser itself, it was observed that technical noise drastically affects the SC coherence, which starts degrading already at pump pulse durations of 50 - 100 fs if a weak pump laser RIN is taken into account [35]
We have presented a detailed numerical study on the impact of technical pump laser fluctuations on octave-spanning ANDi SC generation and its application in ultrafast photonics
Summary
The nonlinear spectral broadening of femtosecond pulses in all-normal dispersion (ANDi) fibers has emerged as an attractive way of realizing low-noise, highly coherent, and octave-spanning supercontinuum (SC) sources [1]. While it was found that the ANDi SC generation dynamics do not significantly amplify technical noise and that the RIN of the SC in the central part of the spectrum can be lower than the RIN of the mode-locked pump laser itself, it was observed that technical noise drastically affects the SC coherence, which starts degrading already at pump pulse durations of 50 - 100 fs if a weak pump laser RIN is taken into account [35] This result could have serious consequences for the applicability of ANDi SC in nonlinear pulse compression and ultrafast photonics in general, since reduced SC coherence is usually associated with poor compressed pulse quality and significant intensity, pulse duration, and timing jitters [9]. We emphasize that our results apply to a wide range of different ultrafast ANDi SC applications, which often involve the manipulation of the SC spectral phase in multi-shot experiments and are subject to the very similar noise limitations
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