Precision optics and mirror figuring

Enlarge one of the mirrors at the heart of an EUV lithography machine to the size of Germany, and its tallest bump would stand a tenth of a millimetre high. That is the surface tolerance required to reflect extreme-ultraviolet light for sub-5nm chipmaking. As of 2025, India imports all of it.

The difficulty is not incremental. A precision-figured mirror must be shaped to nanometre accuracy across its whole surface, then coated with alternating molybdenum-silicon layers that make it reflective at EUV wavelengths — a process produced globally only by ZEISS, Nikon and Canon. ZEISS has spent thirty years developing these optics. The capability sits in just three nations: Germany, Japan and the United States.

India's domestic sector is real but early. Holmarc Opto-Mechatronics, established in 1993, manufactures research-grade mirrors, prisms and coatings using electron-beam evaporation, serving research and industrial markets rather than fab equipment. Hind High Vacuum makes thin-film coatings and optics and has a joint venture with ASM Technologies for semiconductor and solar applications. In the labs, IIT Bombay's nanoelectronics centre has demonstrated focused-ion-beam polishing of silica microdisks — surface finishing at laboratory scale. CSIR-CGCRI's Fiber Optics and Photonics Division runs the country's specialty optical-fibre fabrication, though its work is fibres and gratings, not mirror figuring.

The result is diagnostic: prototype and low-tolerance optics exist; semiconductor-grade precision mirrors and ion-beam figuring do not.

The gap persists because the capability rests on several foundations, and two of the most critical are absent. India produces optical substrate glass, vacuum systems, and CNC polishing — the base and pre-figuring layers. But ion beam figuring equipment, the tool that removes material contactlessly with argon ions to reach nanometre accuracy, is not made domestically. Multilayer Mo/Si EUV coatings, essential for reflectivity, are not produced at all. Precision metrology and interferometry — the ability to measure surface irregularities at nanometre scale — remains emerging. A mirror cannot be figured better than it can be measured, so the metrology gap caps everything above it.

The wider dependence compounds this: over 80% of India's optoelectronic components and precision optical materials are imported, exposing the sector to export controls and trade risk. India's semiconductor mission has approved optoelectronics units for GaN and Mini/Micro-LED, but the precision-optics chain sits outside those programmes.

Closing the gap would mean building upward from the foundations India already holds — metrology first, then indigenous ion-beam figuring, then the multilayer coating process that only three nations command. Each is a hard, sequential climb.