A low-loss, 24-mode laser-written universal photonic processor in a glass-based platform

TL;DR

This paper presents the fabrication of a highly complex, low-loss 24-mode universal photonic processor using femtosecond laser writing, demonstrating its suitability for quantum applications with high fidelity and efficient thermal management.

Contribution

It introduces the first 24-mode universal photonic processor fabricated via femtosecond laser writing, featuring low loss, thermal isolation, and high fidelity for quantum information processing.

Findings

Achieved 4.35 dB average insertion loss across 24 modes

Implemented Haar-random unitary transformations with 99.7% fidelity

Operates efficiently at less than 10 W power

Abstract

We report the fabrication of the first 24-mode universal photonic processor (UPP) realized through femtosecond laser writing (FLW), marking the most complex UPP demonstrated to date. Optimized for quantum dot emission at 925 nm, the device exhibits total insertion losses averaging only 4.35 dB, enabling its direct application in advanced multi-photon quantum experiments. Leveraging the versatility of FLW, we introduce suspended waveguides and precisely engineered 2D and 3D microstructures, significantly enhancing thermal isolation and minimizing power dissipation. As a result, our processor operates efficiently at less than 10 W, requiring only a simple thermo-electric cooler for stable thermal management. The device exhibits exceptional performance after calibration, implementing Haar-random unitary transformations with an amplitude fidelity of 99.7 %. This work establishes FLW-based integrated photonics as a scalable and robust platform for advancing quantum computing, communication, and sensing technologies.