Atmospheric pressure dielectric barrier discharge plasma-enhanced optical contact bonding of different types of optical glasses

Joining processes that do not require joining materials are increasingly needed as an alternative to classic fine cementing in optical production to meet the growing quality requirements. In order to satisfy this demand, processes such as direct bonding (e.g. silicone on insulators) have been adopted successfully from the wafer industry and transferred to fused silica in optical industry after further development [1]. So far, optical contact bonding has only been tested on pure fused silica or coated fused silica [2, 3] where the underlying bonding mechanism is known very well and described in detail [4]. As part of own previous work [5], a process based on a dielectric barrier discharge plasma at atmospheric pressure was developed so that fused silica optics with very sensitive functional optical layers could also be successfully bonded for the first time. In this contribution, the further development of this approach for bonding of Schott's N-BK7 as one of the most common and used optical glasses is introduced. It differs from fused silica in terms of chemical composition, manufacturing qualities and optical properties. It was successfully bonded with the developed process and mentionable high bond strengths were achieved. Possible bonding mechanisms leading to the different bond strengths are discussed here.