High Speed Precise Refractive Index Modification for Photonic Chips through Phase Aberrated Pulsed Lasers

TL;DR

This paper introduces a novel laser writing technique that combines thermal and non-thermal methods, enabling high-speed, high-precision, high-contrast refractive index modifications in photonic chips by manipulating phase aberrations.

Contribution

It proposes a new scheme for laser-induced index modification using phase aberration control, verified through a waveguide formation model, enhancing fabrication speed and precision.

Findings

Achieves scanning speeds of 20 mm/s or higher

Produces high index contrast of 16 x 10^-3

Enables arbitrary cross-section fabrication

Abstract

Integrated photonic chips have significant potential in telecommunications, classic computing, quantum systems, and topological photonics. Direct laser writing offers unique capability for creating three-dimensional photonic devices in an optical glass chip with quick prototyping. However, existing laser writing schemes cannot create index-modified structures in glass that precisely match the laser focal shape while also achieving high scanning speed and high refractive index contrast. Here, we introduce the theory of a refractive index modification scheme that combines the advantages of both traditional non-thermal and thermal regime fabrication methods. We also propose a model of waveguide formation that was verified through a thorough study on the effects of phase aberrations on the laser focus. The presented new photonic chip fabrication scheme uses a novel focal intensity distribution, where pulse energy is relocated to the bottom of a laser focus by manipulating primary and higher order spherical aberrations. The technique can produce index modifications with high scanning speed (20 mm/s or higher), high index contrast (16 x 10-3), and high precision to fabricate with arbitrary cross-sections. This method has potential to expand the capabilities of photonic chips in applications that require small-scale, high precision, or high contrast refractive index control.