Low-cost semiconductor lasers for optical telecommunications

While optics has proven to be the most practical response to the high traffic rate demand for long-haul transmission, its extension to the metropolitan networks down to the home remains an open challenge. The implementation of optics at transmission rate where other technical solutions exist requires cost reduction and simplified manufacturing fabrication. Several steps toward low cost fabrication have been already undertaken: improving the laser resistance to temperature fluctuation in order to remove temperature control elements, improving the laser beam quality to use cheaper or no optics, reducing the number of selection test during fabrication and designing feedback resistant laser. Thus, the implementation of optics into the metropolitan network is today made difficult by the price of the optical components. One of the main source of cost originates from the need for optical isolation. Thus, part of this work was to design single-mode lasers exhibiting a very low sensitivity to external optical feedback for isolator-free transmissions. Other part is now devoted to quantum dot semiconductor lasers which are expected to exhibit many interisting and useful properties such as low threshold current or chirpless behavior. As a result, quantum dot lasers are of prime importance and also open the way to very low cost components. In this paper, we will review the recent progress in all these areas and conclude on the future directions and challenges.