Blue lasers for underwater optical wireless communications

"""Since Shuji Nakamura invented the blue light-emitting diode (LED) in the 1990s, gallium nitride (GaN)-based devices have become key components in medical diagnostics, spectroscopy and quantum applications. GaN LEDs have found extensive research in topics such as visible light communications, however GaN laser diodes are becoming more favourable due to higher modulation capability and higher output powers. These lasers find applications in free space and fibre; however, also have a key role in underwater environments for subsea communication. Due to the low attenuation in water in the blue/green part of the spectrum, GaN laser diodes are the best candidates for low-cost, high speed data transmission underwater. Many current systems use acoustics to communicate underwater, however due to the limited bandwidth, strong signal attenuation and high running costs, this technique has several difficulties. In order to enhance communication between autonomous underwater vehicles (AUVs), allow for seafloor monitoring as well as improving oil and gas exploration and docking systems, faster data rates are required. Currently, megabit per second data rates are achievable, however by moving to GaN optical systems, data rates reaching multiple gigabits per second can be realised, opening doors to new underwater applications.

This project will focus on distributed feedback lasers which can target very precise emission wavelengths and will consist of design and modelling device performance using programs such as LaserMOD and Lumerical, fabricating devices in the James Watt Nanofabrication Centre and ultimately characterising devices for use in underwater applications. System level testing will be investigated looking at the use of multiple lasers and exploiting different modulation schemes.""
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