Microwave radiations (2.45 GHz) are coherent and
polarized.13) They are able to couple with charged particles,
and cause them to be heated up very rapidly. In general,
materials are classified into three groups: reflectors (bulk
metals and alloys), transmitters (fused-silica and fluoropolymers)
and absorbers (inorganic materials, powdered
metals, metal oxides and metal halides).