VUV/O3 assisted single crystal quartz bonding with amorphous SiO2 intermedicate layer for manufacturing optical low pass filter

We proposed a single crystal quartz direct bonding method utilizing amorphous SiO₂ intermediated layers, which can improve heat resistance of the optical low pass filter (OLPF) by novel fabrication method. An amorphous SiO₂ was deposited on the opposite sides of both infrared reflection and anti-reflection coated substrates to prepare the highly activated surfaces. The substrates were bonded at 200 °C after the vacuum ultraviolet (VUV) /O₃ pre-treatment. The bonded sample with amorphous SiO₂ layer shows 5 times higher tensile strength than that without amorphous SiO2 layer while it keeps nearly 100% of light transmittance. These results indicate that amorphous SiO₂ layer could prepare activate surface even in low vacuum bonding condition. This single crystal bonding method will be useful for realizing high performance OLPFs