How To Clean Semrock Optical Filters

Proper cleaning of optical filters requires careful handling, appropriate materials, and controlled techniques to avoid damaging sensitive coatings. The required materials include latex or nitrile gloves, cleanroom wipes, swabs of various sizes, deionized water, HPLC-grade methanol, tweezers, a cloth to remove excess liquid, a fluid dispenser, and a compressed nitrogen air supply.

Begin by gently blowing dust from the optical filter with compressed air before applying any solvents. With gloves on, lay the filters on a cleanroom wipe and handle them only by the edges, using tweezers or gloved fingers.

For general cleaning, choose the correct size cleanroom swab. Dispense methanol into the dispenser top, touch the swab to it, and then dab the swab on a cleanroom wipe to remove excess liquid. Clean the filter surface using a circular motion for round filters or an S-shaped motion for rectangular ones, maintaining constant contact across the surface. Turn the filter over and repeat with the unused side of the swab.

If debris persists, use a fresh swab or the swab’s opposite side, wetted with deionized water, again removing excess liquid before use. Repeat the same gentle motions, ensuring deionized water does not dry on the filter before methanol is applied. For stubborn debris, use different swab sizes, alternating between water and methanol as needed.

Always handle filters gently—never scrub, especially near the edges, as this risks damaging coatings or paint. Repeat the cleaning process on both sides to ensure complete, safe cleaning.