Machining metre-sized gratings with nanometre accuracy

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The proposed research aims at developing a new capability to manufacture structures which are metres in size, but accurate at the nanometre level. This makes use of a new paradigm for precision manufacturing which will combine two separate approaches. The first exploits the repeatable and/or strictly periodic atomic or molecular scale properties of materials to fabricate structures which are accurate on small scales. The second exploits high precision interferometric metrology to position a "writing" head accurately and precisely over large distances. By combining these methods, we aim to "position" the small-scale structures over metre-sized areas using an accurate "location head", thereby guaranteeing much larger-scale order. In this first step towards the development of this novel approach, we will fabricate a number of moderate sized (150 mm diameter) echelle diffraction gratings. These consist of regular and precise sets of miniature grooves on a reflecting surface, and are used in spectroscopy and other measurement and analysis sciences. To do this we will design and build a novel "ruling engine" that will position an optical laser head precisely and accurately, to a few thousandths of a hair's breadth, above the surface of a silicon substrate. The laser head will be precisely guided over the silicon surface so as to set the locations of grooves made by subsequently etching the silicon. When tested, the optical performance of the gratings will be used to refine the active control and position of the writing head, and to validate how successfully positional accuracy can be maintained over larger and larger areas. In the longer term, we aim to develop the system which positions the precision writing head to deliver a more general manufacturing technology so as to allow the writing of arbitrary 2-dimensional patterns on a range of surfaces with unprecedented accuracy. The eventual goal will be to produced a machine capable of "writing" nanometre-accurate 2-d patterns over metre-sized areas.