Method for fabricating a blazed grating
This disclosure relates to a method ( 100 ) for fabricating a blazed grating. The method ( 100 ) comprises providing a substrate and a patterned mask layer ( 110 ) on the substrate, performing primary dry etching ( 120 ) of the substrate such that primary ions are accelerated towards a primary etch direction to impinge on the substrate, and performing secondary dry etching ( 150 ) of the substrate such that secondary ions are accelerated towards a secondary etch direction to impinge on the substrate. A primary projection of the primary etch direction and a secondary projection of the secondary etch direction onto the grating cross-sectional plane extend perpendicular to one and the other of a blaze facet direction and an anti-blaze facet direction, respectively, and ions accelerated towards a direction with a projection onto a grating cross-sectional plane perpendicular to the blaze facet direction are collimated to form a collimated ion beam for etching the substrate.
1 . A method for fabricating a blazed grating comprising a ridge having a blaze facet facing a blaze facet direction and an anti-blaze facet facing an anti-blaze facet direction, the blaze facet direction and the anti-blaze facet direction extending along a grating cross-sectional plane, the method comprising:
providing a substrate and a patterned mask layer on the substrate,
performing primary dry etching of the substrate such that primary ions are accelerated towards a primary etch direction to impinge on the substrate, and
performing secondary dry etching of the substrate such that secondary ions are accelerated towards a secondary etch direction to impinge on the substrate;
wherein a primary projection of the primary etch direction onto the grating cross-sectional plane extends perpendicular to the anti-blaze facet direction and a secondary projection of the secondary etch direction onto the grating cross-sectional plane extends perpendicular to the blaze facet direction and ions accelerated towards a direction with a projection onto the grating cross-sectional plane perpendicular to the blaze facet direction are collimated to form a collimated ion beam for etching the substrate;
wherein the method comprises not revealing a ridge portion of the substrate prior to the process of performing secondary dry etching and the mask layer comprises an inorganic material.
2 . The method of claim 1 , wherein the process of performing primary dry etching comprises forming a groove extending in the substrate along the primary etch direction, the method comprises depositing first material into the groove to form an interstitial feature, and the process of performing secondary dry etching comprises utilizing the interstitial feature as an etch stop.
3 . The method of claim 2 , wherein the process of depositing first material into the groove comprises an atomic layer deposition step.
4 . The method of claim 1 , wherein an interface between the substrate and the mask layer extends along a base plane, and the primary projection or the secondary projection extends perpendicular to the base plane.
5 . The method of claim 4 , wherein the primary etch direction or the secondary etch direction extends perpendicular to the base plane.
6 . The method of claim 1 , wherein an interface between the substrate and the mask layer extends along a base plane, and the primary projection and the secondary projection extend obliquely with respect to the base plane.
7 . The method of claim 1 , wherein the process of providing a substrate and a patterned mask layer comprises providing a plurality of elongated through-holes in a coating arranged on the substrate to form the mask layer, the plurality of elongated through-holes extending perpendicular to the grating cross-sectional plane.
8 . The method of claim 1 , wherein, under primary etching conditions, the primary ions exhibit a first primary chemical reactivity with the mask layer and a second primary chemical reactivity higher than the first primary chemical reactivity with the substrate, and/or, under secondary etching conditions, the secondary ions exhibit a first secondary chemical reactivity with the mask layer and a second secondary chemical reactivity higher than the first secondary chemical reactivity with the substrate.
9 . The method of claim 1 , wherein the blazed grating is formed onto a face of a waveguide for coupling light into the waveguide and/or out of the waveguide.
10 . The method of claim 1 , wherein the blazed grating is formed onto a contact face of a nanoimprint stamp.