Microwave signal generation using self-heterodyning of a fast wavelength switching SG-DBR laser

Microwave signal generation using self-heterodyning of a single wavelength tunable SG-DBR laser is demonstrated. Microwave signals are established by quickly hopping back and forth between two optical wavelengths. These wavelengths are made time coincident through a delay line interferometer. The output of the interferometer is photodetected resulting in a CW microwave signal. This method does not require conventional master-slave laser configurations, external microwave drive sources, or a mode locked laser used to beat dual longitudinal modes. Microwave signals up to 12 GHz have been measured by frequency modulating the phase section of the SG-DBR laser with low frequency RF square wave input currents. Millimeter wave difference frequencies are easily available from the SG-DBR. Temperature robustness of SG-DBR self-heterodyne signals was also investigated. While each laser wavelength by itself changes by 0.12 nm/C (21 GHz/C), the difference frequency temperature coefficient is well less than 30 MHz/C typically.