In a laser gyroscope, an activation wheel has a polygonal cylindrical hub formed by continuous assembly of vertical walls, wherein two adjacent walls of the cylindrical hub between them form a dihedron. Each radial plate of the activation wheel is connected to the cylindrical hub along the edge of a dihedron. The walls are formed with bulging portions, serving for plane-to-plane fixing of one face of the tulip to an optical block, and thin parts allowing a radial displacement degree of freedom of the fixing parts relative to the rim when there is a differential thermal expansion between the tulip and activation wheel. The activation wheel may be produced in a material having a thermal expansion coefficient higher than the tulip, for example steel, with plane-to-plane fixing of the tulip to the activation wheel hub, advantageously by screws, the assembly effectively accommodating the thermal expansion differential between the two materials.