Upper spectrum use boundary on the move [Spectrum Policy and Regulatory Issues]

In the June 2013 issue of this magazine, this column asked "Where Does Radio Spectrum End?" [1]. At the time we pointed out that International Telecommunication Union (ITU) spectrum allocations ended at 275 GHz, although ITU has other rules that refer to spectrum as high as 3 THz [2]. By comparison, various discussions of infrared technology have it beginning as low as 300 GHz (λ = 1 mm) or as high as 3 THz (λ = 100 μm). The IEEE Microwave Theory and Techniques Society publishes a journal, IEEE Transactions on Terahertz Science and Technology, specifically aimed at the frequency range between 300 GHz and 10 THz with the motto: "Expanding the Use of the Electromagnetic Spectrum."