It is well-known that the properties of the supercontinuum (SC) radiation depend critically on the initial pumping
conditions. For instance, if the SC is initiated by noise, namely modulation instability (MI), statistically rare "rogue
waves" can be observed with sizable spectral broadening and intensity enhancement in SC. Interestingly, such rouge
events can be actively controlled by adding an external weak pulse or by modulating the pump-pulse envelopes. In
contrast, we here present that a simple triggering mechanism using an extremely weak continuous wave (CW) can also
achieve such "rogue" enhancement. We experimentally demonstrated that a weak CW trigger (~200,000× weaker than
pump) can considerably broaden the SC bandwidth compared to the untriggered SC case (~100 nm wider). Such
enhancement was found to occur when the CW trigger's wavelength falls roughly within the modulation instability gain
bandwidth. CW triggering also significantly alters the SC amplitude statistics, i.e. from extreme-value statistics in the
untriggered SC to almost normal distribution in the triggered SC. Interferometric measurements also revealed the
improvement in the SC coherence when the SC is CW-triggered. The enhanced SC by minute CW triggering only
requires the CW-wavelength tuning for optimization and eliminates the necessity of high-precision (down to picoseconds)
timing between the pump and the seed as in the pulse-seeding case. It thus offers a more convenient and practical
approach to realize an enhanced and stable SC for many applications, especially in which real-time, ultrafast and singleshot
spectroscopic measurements are essential.
A fiber optical parametric chirped-pulse amplifier (FOPCPA) is experimentally demonstrated. A 1.76 ps signal at 1542
nm with a peak power of 20 mW is broadened to 40 ps, and then amplified by a 100-ps pulsed pump at 1560 nm. The
corresponding idler at 1578 nm is generated as the FOPCPA output. The same medium used to stretch the signal is
deployed to compress the idler to 3.8 ps, and another spool of fiber is deployed to further compress the idler to 1.87 ps.
The peak power of the compressed idler is 2 W, which corresponds to a gain of 20 dB.
An all-optical low-pass filter utilizing cross-gain modulation (XGM) in fiber optical parametric
amplifier (OPA) has been proposed and experimentally demonstrated. In this proposed low-pass filter,
the pump, signal and a continuous-wave probe were launched in the highly-nonlinear fiber (HNLF) to
introduce OPA and thereby XGM effects. Pump, signals and idlers were then being separated and then
filtered. With suitable time delay being introduced into different optical paths, the low-pass filter was
implemented, which was verified with the experimental results of pseudo-random signal. The timing
waveforms of the filtered signal were shown, followed by the transfer function of the low-pass filter's
frequency response. They all showed a good agreement with the numerical results.