A photonic element for a quantum information processing device contains a high-purity silicon layer. The high-purity silicon layer contains integrated rare-earth element (REE) dopants at a concentration of 10.sup.19 cm.sup.3 or less. An optical transition between the lowest crystal field levels of the REE dopants integrated in the high-purity silicon layer exhibits a homogeneous linewidth of 1 MHz or less at a temperature of 4 K or less. A method for producing such a photonic element is also disclosed.

A method for manufacturing a photonic integrated circuit, includes providing a waveguide structure including a core layer having a first refractive index and a first heat conductivity, the core layer arranged between a first and second cladding layers, having a second refractive index lower than the first refractive index and a second heat conductivity lower than the first heat conductivity; etching locally part of the second cladding layer to form a cavity, implanting rare earth elements into at least one of the core layer, the first and the second cladding layer trough the cavity, and annealing the at least one of rare earth doped core layer the first second cladding layers with a first temperature, wherein annealing is performed by a laser beam irradiated into the cavity. A photonic integrated circuit and an alternative method for manufacturing a photonic integrated circuit is provided.

The present disclosure relates to an optical waveguide device and a method for fabricating such a device in the field of mid-infrared photonics. The device comprises a fluoride glass substrate having localized concentrations of a chemical element at inscription points, with a waveguide inscribed along a defined path within the substrate. The waveguide is formed by directing focused ultrashort laser pulses into the substrate and scanning the pulses to induce migration and densification of the chemical element at the inscription points, resulting in a positive refractive index contrast. The fluoride glass substrate may include zirconium fluoride and modifiers such as barium fluoride, aluminium fluoride, and rare-earth elements to enable optical gain. The described technology further encompasses integrated photonic devices, including waveguide lasers comprising mirrors and gratings that define a lasing cavity for use in sensing, communication, and laser systems.