Integrated multimode optical waveguides in glass using laser induced deep etching

Abstract

Glass is an ideal material for optical applications, even though only a few micromachining technologies for material ablation are available. These microstructuring methods are limited regarding precision and freedom of design. A micromachining process for glass is laser induced deep etching (LIDE). Without generating micro-cracks, introducing stress, or other damages, it can precisely machine many types of glass. This work uses LIDE to subtractive manufacture structures in glass carrier substrates. Due to its transmission characteristics and refractive index, the glass substrate serves as optical cladding for polymer waveguides. In this paper, the described fabrication process can be divided into two sub-steps. The doctor blade technique and subsequent additive process step is used in manufacturing cavities with U-shaped cross-sections in glass in order to fill the trenches with liquid optical polymers, which are globally UV-cured. Based on the higher refractive index of the polymer, it enables optical waveguiding in the visible to near-infrared wavelength range. This novel, to the best of our knoowledge, manufacturing method is called LDB (LIDE-doctor-blade); it can be the missing link between long-distance transmissions and on-chip solutions on the packaging level. For validation, optical waveguides are examined regarding their geometrical dimensions, surface roughness, and waveguiding ability, such as intensity distribution and length-dependent attenuation.