A mixing device for mixing a first and second material together to create an output mixture. The applicator is provided with a load chamber 8 extending coaxially with regard to the centre axis of the applicator from an upper end to a predetermined distance from a lower end of the applicator, the load chamber is adapted to receive a load to be heated. It also covers a heating zone of the radiant heater. The first attribute is that the connection has unspecified traffic. The pitch of the regions where first face of the waveguide is not totally internally reflective is substantially an integer multiple of the pitch of the pixels of the spatial light modulator.