# Single-step fabrication of surface waveguides in fused silica with few-cycle laser pulses

## TL;DR

This paper demonstrates a novel method for fabricating surface waveguides in fused silica using few-cycle laser pulses, enabling precise, low-loss photonic structures for integrated circuits.

## Contribution

It introduces a single-step laser fabrication process with sub-10 fs pulses to create subsurface waveguides in fused silica, advancing all-laser manufacturing techniques.

## Key findings

- Achieved optical losses as low as 0.1 dB/mm in air superstrate
- Demonstrated waveguide fabrication using sub-10 fs laser pulses
- Losses increase to 2.8 dB/mm with immersion oil superstrate

## Abstract

Direct laser writing of surface waveguides with ultrashort pulses is a crucial achievement towards all-laser manufacturing of photonic integrated circuits sensitive to their environment. In this Letter, few-cycle laser pulses (with a sub-10 fs duration) are used to produce subsurface waveguides in a non-doped, non-coated fused silica substrate. The fabrication technique relies on laser-induced microdensification below the threshold for nanopore formation. The optical losses of the fabricated waveguides are governed by the optical properties of the superstrate. We have measured losses ranging from less than 0.1~dB/mm (air superstrate) up to 2.8~dB/mm when immersion oil is applied on top of the waveguide.