Harmonic Mixing Properties of Tungsten-Nickel Point-Contacts in the 30–120 THz Frequency Region

Abstract

Tungsten-nickel point-contact (W-Ni) diodes are useful means as rectifiers and harmonic-generator mixers in the frequency region above 4 THz up to about 200 THz. In this paper, an investigation of six harmonic mixing processes is reported using W-Ni diodes as mixers /1/. 4th to 7th order mixing processes have been studied (Table). Processes of the same mixing order shown in the table are different with respect to the mixing products. The behaviour of W-Ni point-contacts as rectifiers and harmonic generators in the mid-infrared have been studied recently /2/. A material specific static current-voltage (I-V) characteristic of the diodes was measured by subtracting the Ohmic portion of 300 Ω /3/. W-Ni diodes showed a nearly parabolic dependence of current on voltage. It was found that the observed beat notes for the 5th order mixing processes exhibited the same bias dependence as the corresponding 5th derivative of the static current-voltage characteristic. These findings initiated an investigation of mixing processes of different mixing orders and products. When the mixing properties in the infrared region were determined by the dc I-V characteristic of the diodes, the beat signal amplitudes measured for a mixing process should follow the corresponding derivative of the dc I-V curve.