By using the simultaneous exposure and development technique, high‐resolution relief gratings with periods as small as 2400 Å have been produced which have grooves cleanly developed down to the substrate surface and exposing wide surface stripes with clearly defined, sharp and narrow photoresist ridges. Such gratings are suitable for use as masks in ion‐beam machining and chemical etching. Results of chemically etched gratings into glass substrates with a 5000‐Å period are presented and prospects of obtaining chemically etched gratings with shorter periods are discussed.