LIGHTWAVE SYNTHESIZER WITH LOCK-IN-DETECTED FREQUENCY REFERENCES

This paper describes a novel lightwave synthesizer system based on the lock-in-detected frequency references such as atomic or molecular spectra. The system employs two semiconductor laser diodes (LD's); one is a frequency-tunable master LD, and the other is a frequency-modulated tracking LD used for stabilizing and tuning the master LD. The lightwave-frequency tuning of the master LD is controlled by a microwave synthesizer. This yields the same frequency stability and accuracy as the lock-in-detected frequency reference at anywhere in the tuning range. By using the 1535.39-nm absorption line of acetylene (C2H2) gas as the reference, a tuning range of over 13 GHz with an absolute frequency stability of better than 10 MHz is demonstrated from a distributed-Bragg-reflector (DBR) LD.