Optoelectronic device

Spectrometric system for detecting radiation in a frequency range lying between 3 gigahertz and 3 terahertz, comprising an optoelectronic device with a conduction constriction for current flow, the conduction constriction having a constriction cross-sectional area A of less than approximately 2 .mu.m.sup.2 and being made of a doped semiconductor layer of carrier mobility .mu. and of layer thickness D, the conduction constriction having an input side and an output side and being contacted on the input side from a metallically conducting input side element and on the output side by a metallically conducting output side element, wherein, in operation, the optoelectronic device is illuminated from a source of coherent radiation and wherein the thickness D of the doped semiconductor layer is larger than approximately one-half and smaller than approximately one-and-a-half times a characteristic path length D.sub.mes, i.e.,

• D.sub.mes *0.5<D<D.sub.mes *1.5
• where D.sup.2.sub.mes is defined by the flux quantum (h/2e) multiplied by the carrier mobility .mu., i.e.
• D.sup.2.sub.mes =(h/2e)*.mu.
• where h is Planck's constant and e elementary charge, wherein, in operation, a light signal to be measured illuminates the optoelectronic device on the input side and cooperates with the source of coherent radiation in order to produce on the output side an electronic mixer signal containing frequency components of the light signal to be measured, with the spectrometric system further comprising a frequency-matched transformer, an amplifier and a spectrometer, and wherein the mixer signal is fed via the frequency-matched transformer to the amplifier which then delivers the mixer signal to the spectrometer which determines the intensities or amplitudes of the frequency components.