Design, simulation and fabrication of low-cost single mode Fabri-Perot laser diode for fiber-to-the-home networks

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The tremendous growth in broadband access services has propelled photonics technology to a new frontier where fiber-based solutions enable not only converged voice, data, and video applications, but also a range of value-added services in local access networks. As a fast-emerging technology that utilizes the vast bandwidth available in optical fibers, these fiber-based access solutions, known as fiber-to-the-home (FTTH) networks, will revolutionize the entire global information network for reaching residential homes and business premises. A major barrier to the widespread deployment of FTTH technology, however, has been the cost. The objective of this proposed research program is to develop cost-effective single longitudinal mode (SLM) semiconductor laser diodes for optical network units (ONUs) in FTTH networks. The program will focus on the investigation of the alternative methods to control the lasing mode in semiconductor lasers with no grating involved. The main idea of achieving the SLM operation is to insert a passive band-pass filter at the rear end of the conventional Fabri-Perot (FP) cavity through etching. It is well known that the total internal reflection (TIR) may happen at a slanted trench introduced across the waveguide. Once we put two such trenches in parallel, tunnelling happens at a set of particular wavelengths at which the reflected waves through the two TIR interfaces cancel out. Therefore, within our interested wavelength range, the slanted double trench structure shows a band-pass filter feature with its spectral peak positions and pass-band width all controlled by its geometrical dimensions. By further aligning the pass-band with one of the targeted FP cavity modes, we achieve the SLM operation. With enhanced immunity of the laser performance from the external feedback and with increased yield, the new design targets a substantial reduction of the fabrication cost of such laser diodes for ONUs which typically account for 70-80% of the cost of a FTTH network. The proposed research, if successful, will therefore have significant impact on the development of the key components of FTTH networks.