Fraunhofer Institute for Reliability and Microintegration IZM
Direct and robust fiber bonding to glass micro-optics, such as GRIN lenses and lens arrays (MLA), can be performed by using a laser welding process. This allows the optical path to be free of adhesive, enabling the transmission of much higher optical power. The typical carbonization issue observed with adhesive methods is completely eliminated. The optical properties of this connection are preserved because neither aging, such as fogging or yellowing, nor shrinkage of the adhesive cause misalignment of the optical components.
The heat input required for joining is induced locally and selectively by a laser. As a result, fiber arrays can be fabricated with extremely high packing densities, limited only by the fiber geometry itself.
Laser welding is also applicable to the bonding of glass capillaries, which is of particular interest in microfluidics applications such as biosensing, analytics and drug delivery. By combining a glass capillary with a microfluidic glass chip, a very low dead volume and high-pressure resistant connection can be realized.
This promising technology has recently been extended to photonic integrated circuits (PIC). Single to multiple fibers in an array can be connected to glass-covered/made waveguide chips, which are extremely relevant for applications such as visible-wavelength spectroscopy and quantum technologies.
These cohesive glass/glass joinings with high optical and mechanical stability are manufactured on an automated assembly prototype machine. The alignment of the parts to be joined is performed as required by passive or active alignment with micrometer precision.
