Epoxy-based optically transparent nanocomposites for photonic packaging

A new optically transparent nanocomposite for photonic packaging and device applications is introduced. The effect of filler particle fraction on the coefficient of thermal expansion (CTE), fracture toughness, and light transmittance of epoxy based optical nanocomposite materials is studied. A nanometer-order silica filler is incorporated into an epoxy matrix with different fractions. The CTE, fracture toughness, and light transmittance at a wavelength range from 300 to 900 nm are measured. The relationship between the measured properties and the filler content is discussed. It is found, as expected, that with the same particle size, increasing the filler fraction results in a decreased CTE and an increased fracture toughness. Actually, the fracture toughness of the nano system is about 10% higher than that of the system with micron-sized fillers at 20% filler loadings. The light transmittance decreases initially with the addition of fillers but there exists a 10% critical filler content above which the further addition of fillers up to 24% does not lead to any further reduction of light transmittance.