Photochemical etching is a high-precision subtractive manufacturing process that selectively removes material from ultra-thin metal foils through photoresist masking and controlled chemical etchant. It forms aperture plates, precision slits, optical masks, alignment fiducials and metal gratings in a single operation. Compared with stamping and laser cutting, photochemical etching applies no mechanical contact, no cutting force and no thermal damage, fundamentally eliminating burrs, residual stress and substrate thermal deformation. This makes it the preferred manufacturing route for spectrometers, laser systems, machine vision and imaging modules, where micron-level tolerance, thin-foil adaptability and high batch consistency are essential.

On the capability level, optical components etching offers a clear parameter window: common foil thickness ranges from 0.02–1.5mm, minimum feature size is generally no less than 1.2–1.5× material thickness, and etching tolerance is about ±10% of material thickness, covering the precision requirements of most optical components. With stable spray etching and in-line inspection, high-density arrays can be formed on large panels in a single run, keeping hole position, slot width and profile highly consistent across the whole plate. For structures that need partial thinning, the half-etch process can machine stepped thickness and grooves without penetrating the substrate, reducing subsequent operations and improving yield, making it a preferred solution for mass production of high-density optical devices.