Efficient Coupling Interfaces in Photonic Systems Enabled by Printed Freeform Micro-Optics

In this presentation, we give an overview of our recent progress in exploiting direct-write two-photon lithography for additive 3D fabrication of freeform micro-optical elements. These elements can be printed with highest precision in direct contact with the facets of photonic integrated circuits or optical fibers, thereby greatly simplifying alignment and improving coupling efficiency. The approach offers new perspectives for a wide variety of applications, ranging from advanced photonic multi-chip modules for high-speed communications and optical sensing to highly efficient astro-photonic systems. We are currently working on transferring the concept from laboratory demonstrations to industrial manufacturing

Micro-lens arrays as tip-tilt sensor for single mode fiber coupling

We introduce a design for a tip-tilt sensor with integrated single-mode fiber coupling for use with the front-end prototype of the iLocater spectrograph at the Large Binocular Telescope to detect vibrations that occur within the optical train. This sensor is made up of a micro-lens array printed on top of a fiber bundle consisting of a central single- mode fiber and six surrounding multi-mode fibers. The design in based on a previous prototype that utilized a multi-core fiber with seven single- mode fibers.1 With this updated design, we are able to achieve a better sensing throughput. We report on the modeled performance: if the beam is perfectly aligned, 69% light is coupled into the central single-mode fiber feeding the scientific instrument. When the beam is not aligned, some of the light will be coupled into the outer sensing fibers, providing the position of the beam for tip-tilt correction. For this design we show that there is a linear response in the sensing fibers when the beam is subject to tip-tilt movement. Furthermore we introduce an adaptive optics testbed, which we call the Koenigstuhl Observatory Opto-mechatronics Laboratory (KOOL), this testbed currently simulates vibrations at the Large Binocular Telescope, and in collaboration we have extended it to allow single-mode fiber coupling tests