Japan has also made some strides in this area, reported here a few months ago.
"Professor Shintake aligned two axis-symmetric mirrors in a straight line and used a total of only four mirrors instead of ten.
"Because highly absorbent EUV light weakens by 40% with each reflection, only about 1% of the energy from the light source reaches the wafer when bounced off ten mirrors while more than 10% does when only four mirrors are used."
I think you have it backwards - light is a term used for specific bands of the EM spectrum. Nobody is calling their FM radio waves light emissions. Unless this is a naming collison with the already established x-rays.
"Professor Shintake aligned two axis-symmetric mirrors in a straight line and used a total of only four mirrors instead of ten.
"Because highly absorbent EUV light weakens by 40% with each reflection, only about 1% of the energy from the light source reaches the wafer when bounced off ten mirrors while more than 10% does when only four mirrors are used."
https://asiatimes.com/2024/08/japan-on-edge-of-euv-lithograp...
Edit: "Substrate said that it has developed a version of lithography that uses X-ray light."