A device is provided for managing heat in an optical element, including: the optical element; a material at a reference temperature; and an intermediate gas layer located directly between the reference-temperature material and the optical element, the intermediate gas layer being located on at least a portion of the thickness thereof in a temporary diffusion state defined by a thickness of the intermediate gas layer, such that the ratio of the mean free path of the gas molecules in the intermediate gas layer over said thickness is between 0.1 and 10. The thickness of the intermediate gas layer is between 10 μm and 5 mm. A corresponding heat-management method is implemented in the device for managing the temperature of an optical element.