Tapered Cavities for High-Modulation-Efficiency and Low-Distortion Semiconductor Lasers

We show that mode structure and cavity geometry in multisegment semiconductor lasers can be tailored to realize high modulation efficiencies as well as low distortion levels in directly modulated semiconductor lasers using the gain-lever effect. Compared with conventional semiconductor gain-lever lasers, the lasers proposed here can have five times higher modulation efficiencies. The second-order harmonic and third-order two-tone intermodulation distortion levels in the proposed lasers are also significantly lower than in conventional gain-lever lasers. We also show that, in the lasers proposed here, unlike in conventional gain-lever lasers, modulation bandwidths and output power levels may not be sacrificed in order to obtain high modulation efficiencies.