Direct comparison of shot-to-shot noise performance of all normal dispersion and anomalous dispersion supercontinuum pumped with sub-picosecond pulse fiber-based laser.

Mariusz Klimczak,Ryszard Buczyński,Rafał Kasztelanic,Krzysztof M Abramski,Grzegorz Soboń

doi:10.1038/srep19284

Abstract

Coherence of supercontinuum sources is critical for applications involving characterization of ultrafast or rarely occurring phenomena. With the demonstrated spectral coverage of supercontinuum extending from near-infrared to over 10 μm in a single nonlinear fiber, there has been a clear push for the bandwidth rather than for attempting to optimize the dynamic properties of the generated spectrum. In this work we provide an experimental assessment of the shot-to-shot noise performance of supercontinuum generation in two types of soft glass photonic crystal fibers. Phase coherence and intensity fluctuations are compared for the cases of an anomalous dispersion-pumped fiber and an all-normal dispersion fiber. With the use of the dispersive Fourier transformation method, we demonstrate that a factor of 100 improvement in signal-to-noise ratio is achieved in the normal-dispersion over anomalous dispersion-pumped fiber for 390 fs long pump pulses. A double-clad design of the photonic lattice of the fiber is further postulated to enable a pump-related seeding mechanism of normal-dispersion supercontinuum broadening under sub-picosecond pumping, which is otherwise known for similar noise characteristics as modulation instability driven, soliton-based spectra.

Highlights

Method[11], since in the anomalous dispersion soliton fission (SF) and soliton self-frequency shift dominate the broadening, while the contribution of the modulation instability (MI) compared to picosecond and nanosecond pumping is strongly suppressed
In this work we report the direct comparison of shot-to-shot noise performance of all-normal dispersion and anomalous dispersion-pumped supercontinuum generation
With the use of interference fringe visibility measurements and dispersive Fourier transformation method (DFT) measurements, we have demonstrated a direct comparison of the phase coherence and the shot-to-shot spectral fluctuations of a soliton-based SC and an SC contained completely in the normal dispersion range of wavelengths of a nonlinear fiber

Summary

Discussion of the phase coherence of supercontinuum

The SC signals, generated in each of the fibers were first launched into an unequal path Michelson-type interferometer in order to investigate the phase coherence properties for the two cases (details on the interferometer setup are provided in the Methods section). Out of the many possible higher order modes, which can be excited in the photonic cladding of our ANDi PCF, the one included in the MM GNLSE simulation experiences dispersion, which stretches the seed signal over the assumed PCF length comparatively to the stretching of the SC pulse (see Methods for examples of dispersion profiles of modes in the photonic lattice calculated for this fiber). This situation is shown in the numerical spectrograms, plotted separately for the SC mode from the core and the seed signal mode in the cladding, at the output of the fiber. Present results call for investigation of the spatiotemporal dynamics in such a “double cladding” nonlinear PCF, which would enable optimization of its structure with respect to the process of seeding from the photonic lattice

Conclusions

Methods

Author Contributions

Additional Information