Attempt to Generate Narrow Linewidth, CW Terahertz Radiation by Using Optical Frequency Comb

We report on an attempt to generate highly stable continuous terahertz (THz) wave by using optical frequency comb (OFC). About 10-nm wide OFC has been generated through a deep phase modulation of a 852 nm laser line in lithium niobate crystal cavity. The multiple optical modes (side bands) of the OFC, which are equally separated from each other by the modulation frequency (=6 GHz) are taken as the frequency reference. When another semiconductor laser is frequency locked, the stability of the difference frequency between the master laser and the second laser is improved on the same order of the RF modulator. An ultra-narrow line and tunable THz radiation source can be achieved by photomixing of this stable difference-frequency optical beat in a photoconductive antenna.