  Using a focused He$^+$ beam for nanopatterning and writing of Josephson
barriers we fabricated specially shaped Josephson junctions of in-line geometry
in YBa$_2$Cu$_3$O$_7$ thin film microbridges with an asymmetry ratio of
critical currents of opposite polarities (non-reciprocity ratio) $\approx 7$ at
optimum magnetic field. Those Josephson diodes were subsequently used as
ratchets to rectify an applied ac current into a dc voltage. We also
demonstrate the operation of such a ratchet in the loaded regime, where it
produces a nonzero dc output power and yields a thermodynamic efficiency of up
to $75\,\mathrm{\%}$. The ratchet shows record figures of merit: an output dc
voltage of up to $212\,\mathrm{\mu V}$ and an output power of up to
$0.2\,\mathrm{nW}$. The device has an essential area $\approx 1\,\mathrm{\mu
m^2}$. For rectification of quasistatic Gaussian noise, the figures of merit
are more modest, however the efficiency can be as high as for the deterministic
ac drives within some regimes. Since the device is based on YBa$_2$Cu$_3$O$_7$,
it can operate at temperatures up to $\sim40\,\mathrm{K}$, where more noise is
available for rectification.
