We report on the fabrication and characterization of coplanar Pb–Cu–Pb nanobridges. In such superconductor (S) – normal metal (N) – superconductor junctions the Josephson coupling is mediated via the proximity effect at the S–N interface. For a junction in the dirty limit (ℓ≪ ξ N where ℓ is the mean free path and ξ N is the coherence length in N) the Josephson current I c is proportional to L/ξ N ·exp(−L/ξ N ). The relation defines an upper limit for the length L of the normal-metal bridge in order to observe Josephson coupling. A Josephson current of up to 750 μA at 1.5 K was observed in junctions with L/ξ N = 0.82 which is only 1/8 of the theoretically expected value. The reduction might originate from oxide layers at the normal metal – superconductor interfaces.
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