WAcrylate polymer
WArsenic triselenide
WArsenic trisulfide
WBarium fluoride
WCadmium selenide
WCalcite
WCR-39
WGallium phosphide
WGermanium
WHydrogen silsesquioxane
WIceland spar
WLiquid crystal
WLithium fluoride
WMagnesium fluoride
WMagnesium oxide
WMETATOY
WNeutron supermirror
WPhosphor
WPoly(methyl methacrylate)
WPolycarbonate
WPotassium bromide
WSapphire
WSpectralon
WSpeculum metal
WSplit-ring resonator
WStrontium fluoride
WStructural coloration
WYogo sapphire
WZBLAN
WZinc selenide
WZinc sulfide