Observing the collapse of super-Bloch oscillations in strong-driving photonic temporal lattices

Super-Bloch oscillations (SBOs) are amplified versions of direct current (dc)-driving Bloch
oscillations realized under the detuned dc- and alternating current (ac)-driving electric fields. A unique
feature of SBOs is the coherent oscillation inhibition via the ac-driving renormalization effect, which is
dubbed as the collapse of SBOs. However, previous experimental studies on SBOs have only been limited
to the weak ac-driving regime, and the collapse of SBOs has not been observed. Here, by harnessing
a synthetic temporal lattice in fiber-loop systems, we push the ac-field into a strong-driving regime and
observe the collapse of SBOs, which manifests as the oscillation-trajectory localization at specific ac-driving
amplitudes and oscillation-direction flip by crossing collapse points. By adopting arbitrary-wave ac-driving
fields, we also realize generalized SBOs with engineered collapse conditions. Finally, we exploit the
oscillation-direction flip features to design tunable temporal beam routers and splitters. We initiate and
demonstrate the collapse of SBOs, which may feature applications in coherent wave localization control
for optical communications and signal processing.