Diamond optics: fabrication and applications

We have developed a method for fabricating almost any type of optical surfaces in diamond. The method consists of the following steps: First, a polymer film, spun onto diamond substrates of optical quality, is patterned by lithographic processes. Next, the surface relief is transferred into the underlying diamond by use of inductively coupled plasma dry etching in an oxygen/argon chemistry. Using this technique, we have successfully demonstrated the fabrication of diamond spherical microlenses, blazed gratings, Fresnel lenses, subwavelength gratings and diffractive fan-out elements. Applications for diamond optics include space technology, high power lasers and optoelectronic devices. In a first real world application we have manufactured subwavelength antireflective gratings which will be tested for use with a future space telescope. The wavelength region of interest will be in the far-IR. Our fabricated antireflective gratings increased the transmitted radiation from 71% to 98% between wavelengths of 21.5 μm and 26.5 μm.