A Key Ingredient Of Modern Fibre Optic Communication: The Semiconductor Laser

Semiconductor lasers are one of the three building blocks of our modern IT world along with fibre optic cable and the Ethernet protocol. Subsea cables use semiconductor lasers to emit light, fibre optic cable to carry and guide it, and the dominant wrapping for optical wavelengths is an Ethernet format. Finally, the IP/TCP protocols enable different networking technologies to operate together as one network. 

Einstein conjectured in 1917 that electrons could be manipulated or stimulated to emit wavelengths at a specific frequency. Later Charles Townes at Bell Labs proposed that light wave intensity could be magnified by passing it through a gas filled cavity. Done in the right way the light would trigger the gas to amplify the light without changing frequency or phase before leaving the chamber. In 1959 at Columbia University he created the immediate predecessor of the semiconductor laser, a maser (microwave amplification by stimulated emission), which used microwaves as both input and output. He also outlined the general semiconductor laser design in a published1958 paper. A lot of this work depends on quantum mechanics and how higher energy levels propel electrons to emit photons. 

Three research teams, including IBM, General Electric, and MIT Lincoln Labs, independently developed working lasers within a few weeks of each other. All three teams used a similar semiconductor design known as a p-i-n diode rectifier and gallium arsenide crystal as the key material. For more details, click here: https://lnkd.in/d5uPPW5v

A semiconductor laser does two key things. First, it raises the optical gain or energy of the light and uses a cavity to ensure the light is polarized or travels as a parallel beam. A good intuitive explanation that provides great insight: https://lnkd.in/d7AmZAQR.