Scanning ion beam etching: A method for the fabrication of computer-generated hologram with nanometric accuracy for aspherical testing

•A scanning ion beam etching (SIBE) method was developed for large-aperture microstructure etching.•Experiments are conducted to verify etching depth accuracy.•High precision CGH fabrication is demonstrated via scanning ion beam etching.•The novel etching method achieves a phase CGH with nanometric precision.