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Optical communications

Single mode and widely tuneable semiconductor lasers are widely used in optical communications. Typically these lasers are based on low perturbation buried gratings (DFB or DBR). Fabricating these lasers generally requires both high resolution processing and complex re-growth steps. However, single mode and tuneable lasers can also be realized by simply introducing gratings in the form of distributed reflective defects (slots) into the ridge of conventional ridge waveguide Fabry-Pérot (FP) laser. This design approach results in significantly simpler fabrication process as well as lower costs.

One aspect of our research is the design of these lasers for optimal performance. The 2D scattering matrix method (SMM) is implemented to optimize gratings and explore various new laser designs. Current laser designs that are being investigated include Vernier tuneable lasers and single mode lasers.

The thermal performance of laser diodes is another area being researched. Currently laser diodes in optical communication systems rely on Peltier coolers to stabilize laser performance. This set-up ensures stable performance but results in a large energy overhead from the Peltier cooler. Alternative set-ups which eliminate the need for a Peltier cooler would significantly improve the overall energy efficiency of an operational laser diode. Solutions based on integrated laser components such as Semiconductor Optical Amplifiers are being researched.

To improve the thermal performance of lasers a good understanding of the thermal properties is necessary. Thermoreflective microscopy techniques are being developed as a means to characterise the thermal properties of the lasers. Using this method optical resolution heat maps can be obtained of electronic devices. This technique will potentially have applications for numerous on-going research projects.

Single mode slotted laser design

SEM of a single mode slotted laser

SEM of the slotted region