Application of Nanoimprint Lithography to Fabrication of Laser Diodes for Optical Communication Network

1-1 Market status of laser diodes for optical communication The recent growth of the Internet, mobile telecommunication, video on demand services, and other information-communication facilities has led to the explosion of worldwide communication traffic, leading to demand for faster and denser communication infrastructures including optical communication networks. Distributed feedback laser diodes (DFB LDs) have been widely used as optical sources in networks because of their high selectivity and stability of wavelength. Though they have mainly been used in long-haul and high-speed networks, they are now increasingly required in metro and end-user fields because of the increasing traffic. Thus, necessity for inexpensive DFB LDs increases rapidly. Sumitomo Electric supplies DFB LDs to the optical communication market as one of the strategic products in optical device business. Innovations in fabrication techniques featuring low cost have been indispensable to meet the demand for inexpensive DFB LDs. 1-2 Nanoimprint lithography Nanoimprint lithography (NIL) is a patterning technique, transferring relief patterns formed on a master mold to resin on a substrate, applicable to forming fine figures with the size of sub-micrometer or smaller. In 1995, Chou et al. indicated that sub-10-nm features could be formed by imprinting, which triggered the start of NIL technology(1). The new technology is promising as a manufacturing process of microand nanodevices because of its high resolution comparable to that of electron beam lithography (EBL) and its much higher throughput than that of EBL. Low initial and running cost is also advantageous to research in various application fields. Various process methods and apparatuses suitable for each application field, for example, next generation storage media(2), optical devices such as wavelength filters(3), and nanofluidics(4), are suggested and studied in the world. 2. Motivation