Fine pitch gratings (200 nm - 240 nm) are required for a variety of devices such as optical filters, semiconductor lasers
and sensors for bio-medical applications. Various lithographic techniques are commercially available for fabricating
gratings, with the choice depending on the type of grating required, cost and volume of manufacture. It is possible to use
state of the art high-resolution projection steppers, common to silicon device manufacturing, for half pitch gratings down
to 65 nm, but for much smaller volume manufacturing of photonic devices these tools have a prohibitive cost of ownership.
Thus, remaining techniques for sub 120 nm half pitch gratings are holography, electron beam lithography, and
nano-imprint lithography. In this paper we compare, characterize, and discuss the practical application of these three
methods. Examples of gratings fabricated at the Canadian Photonics Fabrication Centre (CPFC) are shown as well as
some application examples.
Directly modulated lasers (DMLs) have two high performance applications: 1310 nm 10 Gb/s uncooled and 1550 2.5 Gs/s extended reach. Two key elements are gain coupled gratings and buried heterostructures. Gain coupled gratings simultaneously increase the DML's intrinsic relaxation oscillation frequency and damping, while the buried heterostructure reduces thermal chirp and parasitic capacitance. Large relaxation oscillation frequencies and reduced parasitic capacitance allow 85°C operation; large damping and reduced thermal chirp enable extended reach.