Generating electron beam lithography write parameters from the FORTIS holographic grating solution

Mackenzie Carlson; Stephan McCandliss; Randall McEntaffer; Fabien Grisé; Nicholas Kruczek; Brian Fleming

doi:10.1117/12.2594683

24 August 2021 Generating electron beam lithography write parameters from the FORTIS holographic grating solution

Mackenzie Carlson, Stephan McCandliss, Randall McEntaffer, Fabien Grisé, Nicholas Kruczek, Brian Fleming

Proceedings Volume 11821, UV, X-Ray, and Gamma-Ray Space Instrumentation for Astronomy XXII; 118210Y (2021) https://doi.org/10.1117/12.2594683
Event: SPIE Optical Engineering + Applications, 2021, San Diego, California, United States

Abstract

The Far-UV Off Rowland-circle Telescope for Imaging and Spectroscopy (FORTIS) has been successful in maturing technologies for carrying out multi-object spectroscopy in the far-UV, including: the successful implementation of the Next Generation of Microshutter Arrays; large-area microchannel plate refetectors; and an aspheric dual-order" holographically ruled diffraction grating with curved, variably-spaced grooves with a laminar (rectangular) profile. These optical elements were used to construct an efficient and minimalist two-bounce" spectro-telescope in a Gregorian configuration. However, the susceptibility to Lyman alpha (Ly) scatter inherent to the dual order design has been found to be intractably problematic, motivating our move to an Off-Axis" design. OAxFORTIS will mitigate its susceptibility to Ly by enclosing the optical path, so the detector only receives light from the grating. The new design reduces the collecting area by a factor of 2, but the overall effective area can be regained and improved through the use of new high efficiency reflective coatings, and with the use of a blazed diffraction grating. This latter key technology has been enabled by recent advancements in creating very high efficiency blazed gratings with impressive smoothness using electron beam lithography and chemical etching to create grooves in crystalline silicon. Here we discuss the derivation for the OAxFORTIS grating solution as well as methods used to transform the FORTIS holographic grating recording parameters (following the formalism of Noda et al.1974a,b), into curved and variably-spaced rulings required to drive the electron beam lithography write-head in three dimensions. We will also discuss the process for selecting silicon wafers with the proper orientation of the crystalline planes and give an update on our fabrication preparations.

Conference Presentation

Citation Download Citation

Mackenzie Carlson, Stephan McCandliss, Randall McEntaffer, Fabien Grisé, Nicholas Kruczek, and Brian Fleming "Generating electron beam lithography write parameters from the FORTIS holographic grating solution", Proc. SPIE 11821, UV, X-Ray, and Gamma-Ray Space Instrumentation for Astronomy XXII, 118210Y (24 August 2021); https://doi.org/10.1117/12.2594683

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