Ion etching allows the shape of the grooves on a holographic master grating to be “sculpted” as needed for an application. It is possible to produce blazed holographic gratings with different groove shapes, including triangular and laminar profiles.

The technique uses an ion etching system to mill surface atoms through a holographic mask. This holographic mask is formed by the illumination, and subsequent chemical processing, of a laser generated interferogram in photoresist. The process is compatible with plano, spherical, and aspheric substrates.

Initial Pseudo Sinusoidal,
holographically recorded groove profile

Triangular holographically recorded and
ion etched groove profile

Laminar holographically recorded and
ion etched groove profile

Ion-etched ‘sawtooth’ profiles enhance efficiency at the blaze wavelength in the first order, as well as in the higher diffraction orders. Laminar groove profiles can be designed to minimize or nearly eliminate undesirable second-order efficiency.

Ion-etched gratings can be replicated for quantity production, but they are often used directly as master gratings. In this case the grating grooves are ion-etched directly in the blank itself, resulting in a grating which is very robust, even under the extreme illuminations of the most intense synchrotron light sources.