Patent ID: 8463087

Claim:
A beat signal generating device for use in a Terahertz system, comprising a first monomode laser for generating radiation of a first wavelength; a second monomode laser for generating radiation of a second wavelength different from the first wavelength; a first and a second output port; a phase modulating unit for modifying both the phase of radiation generated by the first laser and the phase of radiation generated the second laser, wherein the beat signal generating device is configured in such a way that the radiation generated by the first laser is transmitted through the second laser and superposed with the radiation generated by the second laser at the second output port, and the radiation generated by the second laser is transmitted through the first laser and superposed with the radiation generated by the first laser at the first output port, such that a first beat signal will be emitted at the first output port and a second beat signal will be emitted at the second output port, wherein the phase between the first and the second beat signal can be adjusted by means of the phase modulating unit.