Free-space and underwater GHz data transmission using AlGaInN laser diode technology

Abstract

Laser diodes fabricated from the AlGaInN material system is an emerging technology for defence and security applications; in particular for free space laser communication. Conventional underwater communication is done acoustically with very slow data rates, short reach, and vulnurable for interception. AlGaInN blue-green laser diode technology allows the possibility of both airbourne links and underwater telecom that operate at very fast data rates (GHz), long reach (100's of metres underwater) and can also be quantum encrypted. The latest developments in AlGaInN laser diode technology are reviewed for defence and security applications. The AlGaInN material system allows for laser diodes to be fabricated over a very wide range of wavelengths from u.v., ~380nm, to the visible ~530nm, by tuning the indium content of the laser GaInN quantum well. Ridge waveguide laser diode structures are fabricated to achieve single mode operation with optical powers of >100mW. Visible light communications at high frequency (up to 2.5 Gbit/s) using a directly modulated 422nm Galliumnitride (GaN) blue laser diode is reported in free-space and underwater.

A review of gallium nitride LEDs for multi-gigabit-per-second visible light data communications

“…Underwater VLC channel suffers from high attenuation and multiple scattering. Scattering and attenuation are strongly wavelength dependent, and hence underwater communication systems use blue-green (400-550 nm) LEDs to exploit the low absorption in this wavelength region [316][317][318].…”