Abstract: A waveguide with a hollow core (16) delimited by a closed contour includes a succession of arcs (20) of negative curvature, each arc including a chord (24), characterized in that the contour of the hollow core (16) includes small arcs (PA) and large arcs (GA) arranged alternately, each arc (20) being symmetric with respect to a straight line passing through the center (18) of the hollow core (16) and the middle of the chord (24) thereof, the ratio b=2Ra/C of the large arcs being greater than 0.9 for the large arcs (GA), Ra corresponding to the maximum distance between the chord (24) and the arc (20), C corresponding to the length of the chord (24).

Abstract: A waveguide with a hollow core (16) delimited by a closed contour includes a succession of arcs (20) of negative curvature, each arc including a chord (24), characterized in that the contour of the hollow core (16) includes small arcs (PA) and large arcs (GA) arranged alternately, each arc (20) being symmetric with respect to a straight line passing through the centre (18) of the hollow core (16) and the middle of the chord (24) thereof, the ratio b=2Ra/C of the large arcs being greater than 0.9 for the large arcs (GA), Ra corresponding to the maximum distance between the chord (24) and the arc (20), C corresponding to the length of the chord (24).

Abstract: A device for the excitation of a gas medium (10) contained in a casing (12), the device being coupled to the casing (12) and disposed outside same and including an applicator that can generate lateral excitation inside the casing (12) over at least a portion thereof. The device is characterized in that the casing (12) is a hollow-core photonic dielectric structure (16), in which the core has a diameter smaller than 300 ?m, and in that the applicator is of the microwave type and can be used to generate a surface wave that can create and confine a microplasma from the gaseous medium contained in the casing (12).

Abstract: A device for the excitation of a gas medium (10) contained in a casing (12), the device being coupled to the casing (12) and disposed outside same and including an applicator that can generate lateral excitation inside the casing (12) over at least a portion thereof. The device is characterized in that the casing (12) is a hollow-core photonic dielectric structure (16), in which the core has a diameter smaller than 300 ?m, and in that the applicator is of the microwave type and can be used to generate a surface wave that can create and confine a micro-plasma from the gaseous medium contained in the casing (12).