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Terahertz frequency generation by frequency mixing in semiconductor optical amplifiers

We describe the generation of terahertz optical frequency comb using the spontaneous emissions from a semiconductor optical amplifier as the signal source. The source drives an all-fiber LYOT-Sagnac birefringent fiber. This transforms the broad band source into a discrete set of evenly spaced frequencies. The output of the Sagnac loop mirror is then coupled to fiber pigtailed Faraday Mirror reflecting the optical frequency comb back into the optical amplifier for further amplification. The method resulted in generating optical frequency comb ranging from 183THz to 213 THz with frequency spacing of 560 GHz.