Metal direct nanoimprinting for photonics

In this paper metal direct nanoimprinting (embossing) for the production of metallic microparts is discussed, with a main focus on its suitability for the fabrication of metal-containing optical devices such as photonic crystals, plasmon waveguides or chiral structures. Silver and gold were chosen, since they have the lowest light absorption in the near infrared and visible range. They are also easily formable due to their good ductility, which can be further enhanced by processing at elevated temperature. The mold material, which may form part of the optical device, usually consisted of silicon, but other dielectric materials such as silicon oxide and silicon nitride were also successfully tested.Cylindrical and line-shaped holes with lateral dimensions down to 250 nm and aspect ratios of up to 5 were etched in silicon wafers. All the structures were successfully filled with silver and gold, and the filling of smaller dimensions is also deemed possible. This technique is therefore suitable for producing metal-containing optical devices working in the infrared, at least down to the standard telecom wavelength of 1.5 μm, which requires metallic dimensions of 200–300 nm.