Using a focused ${\mathrm{He}}^{+}$ beam for nanopatterning and writing of Josephson barriers, we fabricated specially shaped Josephson junctions of in-line geometry in ${\mathrm{YBa}}_2{\mathrm{Cu}}_3{\mathrm{O}}_7$ thin film microbridges with an asymmetry ratio of critical currents of opposite polarities of approximately $7$ at the optimum magnetic field. Those Josephson diodes were subsequently used as ratchets to rectify an applied alternating 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%. The ratchet shows record figures of merit: an output dc voltage of up to $212\text{μ}\mathrm{V}$ and an output power of up to $0.2\mathrm{nW}$. The device has an essential area of approximately $1\text{μ}{\mathrm{m}}^2$. 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 ${\mathrm{YBa}}_2{\mathrm{Cu}}_3{\mathrm{O}}_7$, it can operate at temperatures up to approximately $40\mathrm{K}$, where more noise is available for rectification.

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• Electrical properties
• Transport phenomena
• Brownian ratchet
• Cuprates
• Diodes
• Josephson junctions
• Nanotechnology
• Focused ion beam