Spectrally-resolved statistical characterization of seeded supercontinuum suppression using optical time-stretch

Abstract

Real-time experimental measurements of the spectrally-resolved noise properties of supercontinuum (SC) have been challenging because of the lack of ultrafast optical spectrometer technologies. Understanding the SC noise is increasingly important because it not only can gain new insight of the complex spectral dynamics of SC generation, but also provides clues to search for stable SC source. Driven by the intense interest in the active seeding mechanism for SC generation, we experimentally demonstrate real-time spectrally-resolved, broadband, statistical characterization of minute continuous-wave (CW) seeded SC, enabled by an ultrahigh-speed spectral acquisition technique called optical time-stretch (OTS). The shot-to-shot statistical analysis shows that the seeded SC exhibits a general compromise between SC bandwidth and spectral stability. OTS also allows us to experimentally identify the seeding condition for SC suppression, in which the spectral broadening is mainly contributed by the cascaded parametric process that delays Akhmediev Breather breakup process and subsequent soliton self-frequency shift. Additionally, the characteristic spectral signature of the Raman solitons, which are becalmed by the minute CW seed, can be clearly captured in real-time by OTS operated at a spectral acquisition rate as high as 20 MHz. We anticipate the OTS technique could provide further new insights for understanding more complex mechanisms of seeded-SC generation which can be examined experimentally.

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

“…Femtosecond laser pumping is considered the most straightforward method 11 , since then in the anomalous dispersion soliton fission (SF) and soliton self-frequency shift dominate the broadening, while the contribution of the MI compared to picosecond and nanosecond pumping is strongly suppressed. More elaborate solutions are based on seeding, which introduces a seed wavelength component with deterministic phase in a four-wave mixing process 12 13 14 . An alternative approach makes use of fiber tapers, in which initial broadening occurs in the anomalous dispersion-pumped regime, and evolves into normal dispersion broadening during propagation along the taper 15 .…”

Real-time characterization of spectral coherence of ultrafast laser based on optical time-stretch

“…More practically, deeper understanding of these underlying processes could provide insight into how to manipulate them and thus pave the way for developing highly stable (shot-to-shot), low-noise pulsed lasers, especially valuable for applications requiring high temporal stability, such as ultrafast imaging and spectroscopy [2]. Note that seeded/triggered SC has already been studied with time-stretch spectral intensity measurements, especially in the context of "stimulating" or "inhibiting" rogue wave formation [10,51], which give clues for SC enhancement or suppression [27]. Again, the dynamics of spectral coherence have not been fully characterized in many of these highly nonlinear SC generation processes.…”

“…While optical time stretch has opened a new avenue for spectrally-resolved single-shot characterization at an ultrahigh speed, majority of the existing effort focuses on intensity measurement and analysis [24][25][26][27]. Although phase retrieval from single pulses is possible with iterative computational techniques [28], the phase accuracy is inherently limited by the time-bandwidth product, not to mention that the increased experimental complexity due to the required multiple/cascaded measurements [29].…”

Coherent supercontinuum generation in soft glass photonic crystal fibers

“…A low-power seed signal can also be in-coupled to the fiber (often a continuous-wave signal) at a wavelength corresponding to SC fragments affected by MI amplification of noise. The purpose of the seed signal is delivering spectral components with pulse-to-pulse deterministic phase [26][27][28]. An alternative way is the use of a tapered fiber as the nonlinear medium [29].…”