Abstract

High-speed semiconductor lasers are promising candidate to realize low cost data communication systems. Operation speed of semiconductor lasers is, however, limited by their resonant frequency. The frequency can increase by setting laser cavity structure appropriately. Shortening the laser cavity is one way to increase the frequency. But the operation speed was limited to less than 40 GHz due to the heat problem. Recently photon-photon resonance (PPR) effect is focused to increase response speed of semiconductor lasers. Second resonant peak can be introduced to the laser's response by combining external cavities to semiconductor lasers[1]. However PPR effect cannot be introduced effectively when PPR frequency is set far from resonant frequency due to steep degradation in modulation response of semiconductor laser at higher modulation frequency than resonant frequency. To overcome this problem we proposed hybrid modulation scheme, where laser injection current and intra-cavity optical loss are modulated simultaneously. The hybrid modulation semiconductor laser can make response degradation gently at high modulation frequency region and can introduce PPR effect effectively. Figure 1 shows the schematic structure of hybrid modulation semiconductor laser. It consist of DFB laser section and intra-cavity loss modulation section. The intra-cavity loss modulation section consist of electro-absorption waveguide and its optical propagation loss can be controlled by controlling applied reverse bias voltage. The section also acts as external cavity and PPR effect can be introduced.

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