  Optical control of correlated electronic states promises unprecedented
tunability of novel functional materials. Tailored optical excitations can
steer a system along non-equilibrium pathways to metastable states with
specific structural or electronic properties. A much-desired feature is the
reproducible and ultrafast switching to functional states. The light-induced
hidden state of 1T-TaS$_{2}$, with its strongly enhanced conductivity and
exceptionally long lifetime, represents a unique model system for studying the
switching of correlated electronic states using femtosecond optical stimuli.
However, despite intense investigation, the switching mechanism and the
structural origins of the distinctive electronic properties of the hidden state
have not been fully uncovered. Here, we use surface-sensitive electron
diffraction in combination with a femtosecond optical quench to reveal
coexistent charge-density wave chiralities as a new structural feature of the
hidden state. We find that a single-pulse optical quench produces a state with
long-range structural order and different weights of the two chiral
enantiomorphs of the charge-density wave. Harnessing a double-pulse optical
quench, we trace the origin of the mixed chirality to the transient electronic
excitation of the host crystal. The coexistent long-range-order of both
chiralities suggests the presence of extended heterochiral charge-density wave
interfaces, which results in a higher-level, fractal-type moir\'{e}
superstructure. Density functional theory simulations for such a charge-density
wave moir\'{e} superstructure reveal multiple flat bands, Dirac cones, and a
kagome electronic subsystem around the Fermi energy. Our findings shed light on
novel electronic properties gained by chiral interface engineering, and create
avenues for light-induced moir\'{e} superstructures in quasi-two-dimensional
materials.
