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Jupiter's moon Europa likely hosts a saltwater ocean beneath its icy surface. Geothermal heating and rotating convection in the ocean may drive a global overturning circulation that redistributes heat vertically and meridionally, preferentially warming the ice shell at the equator. Here we assess the previously unconstrained influence of ocean‐ice coupling on Europa's ocean stratification and heat transport. We demonstrate that a relatively fresh layer can form at the ice‐ocean interface due to a meridional ice transport forced by the differential ice shell heating between the equator and the poles. We provide analytical and numerical solutions for the layer's characteristics, highlighting their sensitivity to critical ocean parameters. For a weakly turbulent and highly saline ocean, a strong buoyancy gradient at the base of the freshwater layer can suppress vertical tracer exchange with the deeper ocean. As a result, the freshwater layer permits relatively warm deep ocean temperatures.

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We present the analyses of surface plasmon polaritons (SPPs) coupling induced interference in metal/dielectric (M/D) multilayer metamaterials and techniques to improve the performance of sub-wavelength plasmonic lithography. Expressions of beam spreading angles and interference patterns are derived from analyses of numerical simulations and the coupled mode theory. The new understandings provide useful guidelines and design criteria for plasmonic lithography. With proper layer structure design, sub-wavelength uniform periodic patterns with feature size of 1/12 of the mask's period can be realized. High pattern contrast of 0.8 and large field depth of 80 nm are also demonstrated numerically by considering the SPPs coupling in the photoresist. Both high contrast and large image depth are crucial for practical application of plasmonic lithography.