Evaluation of area scaling of the reactive ion-plasma etched astronomical diffraction gratings

Over the past two years, we have been developing the Reactive Ion-PLasma Etched (RIPLE) grating technology. Early on, we demonstrated the process to be a highly predictive, based on experimental verification of the near theoretical super-broadband diffraction efficiency from a proof-of-concept 1x1 sq. inch RIPLE grating. All measured 0^th and 1^st order diffraction efficiency scans from this prototype matched numerical model predictions within 2% at 1σ-level, indicating a highly stable process and non-significant level of defects on the device. The fabrication process was shown to be repeatable over the same area and grating form parameters, and we extended it to larger grating areas with deep-etched grating line features. We demonstrated area scaling to 2x2 sq. inch via an iterative etching technique and recently reached the primary 4x4 sq. inch target. We discuss the evaluation of this area scaling effort.