Making nanostructures

Once a photonic nanostructure has been designed, we need to manufacture it. The process, for the example of a diffraction grating discussed in the previous article, is shown in the video above.

We first use electron-beam lithography to remove unwanted material. As we have seen in the context of electron microscopy, beams of electrons can be focused into tiny spots of nanometre size. We use such focused electron beams to define our structures. The beam of electrons is scanned across the image to expose the pattern sequentially. The sample is coated in a resist that is sensitive to electron exposure and therefore only the desired areas are removed to reveal the design.

The specific function we aim to achieve with these nanostructures requires careful control of their dimensions. For example, some of our gratings operate at a scale of half the wavelength of the light we are intending to use. For visible and near-infrared light of a wavelength less than 1µm, this means that the grating period may be 500 nm or smaller, and the slits may be as small as 100 nm.