# Direct laser written polymer waveguides with out of plane couplers for optical chips

## TL;DR

This paper demonstrates the fabrication of polymer waveguides using two-photon lithography, achieving high-density integration, low losses, and innovative 3D couplers suitable for complex optical chip networks.

## Contribution

It introduces a novel 3D coupler design and detailed performance analysis of polymer waveguides fabricated by direct laser writing.

## Key findings

- Waveguides with bend radii down to 40 μm and insertion losses around 10 dB.
- Loss coefficients smaller than 0.81 dB/mm enabling dense integration.
- Compatibility of the waveguide material with quantum emitter integration.

## Abstract

Optical technologies call for waveguide networks featuring high integration densities, low losses, and simple operation. Here, we present polymer waveguides fabricated from a negative tone photoresist via two-photon-lithography in direct laser writing, and show a detailed parameter study of their performance. Specifically, we produce waveguides featuring bend radii down to 40 {\mu}m, insertion losses of the order of 10 dB, and loss coefficients smaller than 0.81 dB/mm, facilitating high integration densities in writing fields of 300 {\mu}m x 300 {\mu}m. A novel three-dimensional coupler design allows for coupling control as well as direct observation of outputs in a single field of view through a microscope objective. Finally, we present beam-splitting devices to construct larger optical networks, and we show that the waveguide material is compatible with the integration of quantum emitters.