Evaluating adhesive and ultrashort pulsed laser (USP) techniques for optomechanical glass assemblies

Bonding materials is a critical manufacturing process with novel approaches often required for high specification, repeatability, cost etc. [1]. Optomechanical assemblies such as lasers, astronomical instruments, telescopes and interferometers typically require precise orientation and positioning of the optical components to within very strict tolerances of a few micrometers for the assemblies to function properly [2]. The most widely used technique for joining optics to assemblies in the manufacturing of optical and laser systems is adhesive bonding, however, there are challenges with repeatability, contamination, outgassing, creep and degradation. Ultrashort pulsed laser (USP) processing has become an attractive alternative to this process in recent years. When used for welding it removes the requirement to add an adhesive interlayer between the components [3]. When used for selective laser etching (SLE) it can reduce the need for bonding, or provide for mechanical alignment features [4]. However, such bonding and processing techniques can have a significant effect on the performance and/or survivability of the finished product.

In this work, we present the recent results on bonding fused silica components using three different techniques; adhesive bonding, ultrashort pulsed laser welding, and mechanical fixtures manufactured using selective laser etching. The parts used in these experiments are designed to imitate typical components in a size range of optomechanical assemblies typically of the order of ½” to 1”. The evaluation of stress induced birefringence in the optical components is presented with the aim of understanding fatigue during thermal cycling, alongside accelerated lifetime tests and shear strength tests of the bonded components.