Optical mixing of two optical waves from a helium-neon gas laser to generate a stable continuous-wave radio-frequency signal

An approach to the generation of a radio-frequency signal using a dual longitudinal mode helium-neon (HeNe) gas laser and the optical mixing technique is proposed and demonstrated. Several approaches using lasers and photodetectors with different characteristics give a detailed insight into the potential and utility of the optical mixing of two optical waves to generate a radio-frequency reference source. A low-phase-noise radio-frequency signal is observed by a signal-source analyzer because the two lasing modes share the same gain medium in the few-centimeters-long cavity and the relative phase irregular shifting fluctuations between the two wavelengths are low. The observed phase noise below −100 dBc/Hz at the offset of 1 kHz from the continuous-wave tone at the central frequency of 723 MHz indicates that the dual-mode-cavity gas laser efficiently suppresses the wavelength fluctuations between the lightwave modes, enabling a stable radio-frequency signal to be generated.