Thermally-Reconfigurable Quantum Photonic Circuits at Telecom Wavelength by Femtosecond Laser Micromachining

TL;DR

This paper demonstrates the fabrication and thermal reconfiguration of femtosecond laser written quantum photonic circuits at telecom wavelengths, achieving high-fidelity manipulation of quantum states for future quantum networks.

Contribution

It introduces a method to create thermally reconfigurable quantum photonic circuits in glass using femtosecond laser writing, with high-performance quantum state control.

Findings

High fringe visibility (>95%) in quantum interference experiments.

Successful thermal tuning of femtosecond laser written circuits.

Potential for reconfigurable quantum photonic devices at telecom wavelengths.

Abstract

The importance of integrated quantum photonics in the telecom band resides on the possibility of interfacing with the optical network infrastructure developed for classical communications. In this framework, femtosecond laser written integrated photonic circuits, already assessed for quantum information experiments in the 800 nm wavelength range, have great potentials. In fact these circuits, written in glass, can be perfectly mode-matched at telecom wavelength to the in/out coupling fibers, which is a key requirement for a low-loss processing node in future quantum optical networks. In addition, for several applications quantum photonic devices will also need to be dynamically reconfigurable. Here we experimentally demonstrate the high performance of femtosecond laser written photonic circuits for quantum experiments in the telecom band and we show the use of thermal shifters, also fabricated by the same femtosecond laser, to accurately tune them. State-of-the-art manipulation of single and two-photon states is demonstrated, with fringe visibilities greater than 95%. This opens the way to the realization of reconfigurable quantum photonic circuits on this technological platform.