1. A device (100) for processing a medium, in particular for cleaning fluids such as water or air, or surfaces, comprising: a) a waveguide as a substrate (110) with a surface (111) of the substrate through which energy is transferred during the operation of the device (100)； b) a photocatalytic layer (120), which is located on the surface (111) of the substrate and with which medium can contact, characterized in that an intermediate layer (130) is located between the substrate (110) and the photocatalytic layer (120) while at the interface between said intermediate nym layer and the substrate occurs during the total internal otrazhenie.2. A method for processing a medium, in particular, for cleaning fluids such as water or air, or surfaces, comprising the following steps: a) transferring light energy from a waveguide as a substrate (110) through an intermediate layer (130) to a photocatalytic layer (120), which located on the surface (111) of the substrate (110)； b) the initiation of reactions in the medium upon contacting it with the photocatalytic layer (120) .3. The device (100) according to claim 1 or the method according to claim 2, characterized in that the light energy is transferred from the substrate (110) to the photocatalytic layer (120) by damped waves. 4. The device (100) according to claim 1 or the method according to claim 2, characterized in that the light source (150) is provided for generating light that is introduced into the substrate (110) .5. A device (100) or method according to claim 4, characterized in that the light source (150) comprises an LED and / or a laser diode. 6. A device (100) or a method according to claim 4, characterized or characterized in that a reflective element (151, 152, 153 is provided between the light source (150) and the substrate (110)1. Устройство (100) для обработки среды, в частности, для очистки текучих сред, подобных воде или воздуху, или поверхностей, содержащее:a) волновод в качестве подложки (110) с поверхнос
