A novel method for fabrication of dual-blazed diffraction gratings using mosaicking technique

Efficiency of a diffraction grating is an important characteristic governed by the groove period, groove shape and grating material. Generally, gratings are designed to have a peak efficiency at a particular wavelength and diffraction order. However, it is possible to fabricate gratings which have the same groove period across the grating, but different groove shape or profile in different sections of the grating. This results in an efficiency curve which is a weighted average of the efficiency performance of each individual section under illumination. The simplest example of such a grating is a dual-blazed grating, which has two sections with two different groove shapes or profiles. This work presents a new method for fabricating dual-blazed gratings by mechanically aligning two gratings, bonding them using epoxy, and finally obtaining a monolithic replica, maintaining optical control of the wavefront throughout all process steps. This technique provides the ability to tailor grating efficiencies over a broad wavelength range to achieve efficiencies that are unavailable to single-blazed gratings. Subsequently, monolithic dual-blazed gratings can be replicated using a proprietary replication process. The seam between the two gratings can be oriented parallel to the grooves, perpendicular to them or any other random orientation. Additionally, the effect of the seam orientation between two sections on scatter properties is investigated in this work. It is observed that when the seam is not parallel, scattered light strongly decreases in the diffraction plane due to scattering of light from the seam in direction away from it.

Automated summary

A new method for fabricating dual-blazed gratings is introduced, which involves aligning and bonding two gratings to obtain a monolithic replica with maintained optical control. This technique allows for tailoring grating efficiencies over a broad wavelength range. Furthermore, the effect of the seam orientation between two sections on scatter properties is investigated.