An open‐structure W‐GaAs Schottky point‐contact diode was tested as an efficient mixer device for visible laser light and microwave radiation. Beat signals between the lines of a krypton ion laser at 568 nm, and of a dye ring laser and the emission of a backward wave oscillator at 85.4 GHz, showed signal‐to‐noise ratios of 50 dB. Microwave harmonics generated in the same diode could be mixed with the two laser lines up to frequency differences of 430 GHz (i.e., 5th harmonic). A comparison with other mixers for the visible spectral range is given.