Optical Substrates & Windows

Optical Flats
Laser grade standard optical substrates have a laser polish on one surface and a commercial polish or are ground on the back surface. ("Window" substrates are laser polished on both surfaces). The polishing techniques used produce a super polish with a surface roughness of 5 to 10 Angstroms and very low scatter. Material of 6 to 7 times grit diameter is removed during each grind and polish process to ensure very little sub-surface fracturing. This results in a substrate that withstands high energy laser radiation.

Reference standard master flats are precision polished, uncoated optical flats used as optical reference surfaces in labs and on production floors. These master flats are either fused silica or Zerodur. The Zerodur substrates have essentially a zero coefficient of thermal expansion over a wide ambient temperature range. They are the most stable substrate available. Each master flat comes in a protective box and is supplied with an interferogram that shows the exact measured flatness of the master surface. These flats are polished to λ/20 at 633nm and are parallel within 3 arcmin.

Wedged Substrates
Wedge substrates are available in BK7, Fused Silica and Excimer grade fused silica. The wedge angle reduces reflection from the rear surface. A variety of wedge angles are available, including 0.5, 1, 2 and 3 degrees.

Windows
Windows create a physical barrier between environments such as air to water, vacuum to air, or one gas to another. The ideal window allows the optical beam to pass through without making any changes to the wavelength distribution or wavefront of the beam. To do this, windows need high transmittance, low wavefront distortion and low scatter. Sapphire windows resist scratches and transmit from the visible to 2 microns. Fused Silica windows have the broadest transmission range available. Glass windows are the ideal choice for high quality visible applications.