Size is a matter of definition. Depending on the industrial sector, some millimeters can be a tolerance or determine the function.
A hundred years ago the idea of cutting material without touching it seemed to be science fiction.
In principle optical designers differ between optical glass and two types of fused quartz glass. On the one hand melted minerals containing silicon oxide are the basic for natural fused quartz.
Lasers have been established as universal tools in countless applications and the numbers are steadily increasing.
Aspheres offer the great advantage to accomplish monochromatic imaging tasks with one optical element where multiple lens elements would otherwise be needed.