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

宽带接入服务的巨大增长将光子技术推向了一个新的前沿，基于光纤的解决方案不仅可以实现融合的语音、数据和视频应用，还可以在本地接入网络中提供一系列增值服务。作为一种利用光纤中可用的巨大带宽的快速新兴技术，这些基于光纤的接入解决方案（称为光纤到户（FTTH）网络）将彻底改变整个全球信息网络，以覆盖住宅和商业场所。然而，FTTH技术广泛部署的一个主要障碍是成本。本研究计划的目标是开发用于FTTH网络中的光网络单元（ONU）的具有成本效益的单纵模（SLM）半导体激光二极管。该计划将侧重于研究控制半导体激光器中不涉及光栅的激光模式的替代方法。实现SLM工作的主要思想是通过刻蚀在传统法布里-珀罗腔的后端插入一个无源带通滤波器。众所周知，全内反射（TIR）可以发生在跨波导引入的倾斜沟槽处。一旦我们将两个这样的沟槽平行放置，隧道效应就会在一组特定的波长处发生，在这些波长处，通过两个TIR界面的反射波相互抵消。因此，在我们感兴趣的波长范围内，倾斜双沟槽结构显示出带通滤波器的特征，其光谱峰位置和通带宽度都由其几何尺寸控制。通过进一步对准的通带与目标FP腔模式之一，我们实现了SLM操作。随着激光器性能对外部反馈的增强免疫力以及产量的增加，新设计的目标是大幅降低用于ONU的这种激光二极管的制造成本，这种激光二极管通常占FTTH网络成本的70-80%。如果这项研究成功，将对FTTH网络关键组件的发展产生重大影响。

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.