Iridian Spectral Technologies (Ottawa, ON, Canada) has authored a white paper entitled "Large format NBPF--a uniformity challenge" describing its demonstration and manufacture of its extremely uniform large format (130 mm) narrow bandpass filter (NBPF).
RELATED WHITE PAPERS: http://www.laserfocusworld.com/whitepaper-listing.html
An excerpt of the white paper follows:
Large format (>100 mm diameter), narrow bandpass filters (NBPF) are required in many fields. Applications requiring a large collection aperture drive the need for large collection optics, however high wavelength selectivity provided by narrow, flat-top bandpass optical filtering (http://www.laserfocusworld.com/articles/2016/05/iridian-spectral-technologies-laser-reflection-glasses-work-with-reflection-in-the-high-power-nir.html) is also required to facilitate specific and selective analysis of a phenomena or substance of interest. The diversity of applications of these optics include earth observation remote sensing (whether satellite imaging or UAV mounted LIDAR), astronomical/solar imaging, UV micro-lithography tools, and live animal biological (fluorescence) imaging …
Iridian has addressed each of these challenges and has recently demonstrated the successful design and manufacture of an environmentally stable 1.72 nm-wide (FWHM) NBPF centered near 780 nm to within 20 pm of the wavelength target over an operating clear aperture >125 mm in diameter.
SOURCE: Iridian Spectral Technologies; https://www.iridian-optical-filters.com/