A New Tunable Coherent FIR-THz Source

Bloch oscillations are one of the most basic effects in solids: If an electron is put into a static field, it will accelerate until it reaches the edge of the first Brillouin zone. It is then Bragg-reflected and returns to its original position, where it starts to accelerate again. The resulting spatial oscillation has never been observed in bulk solids since it is suppressed by scattering events. Bloch oscillations have recently been observed in semiconductor superlattices. These experiments demonstrate that the frequency of the oscillations is tunable over a large range by the static electric field and that the electron oscillations lead to emission of THz radiation, which is promising for applications.

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