Why is facet passivation of laser diodes necessary?

Sheaumann Process Engineer

Facet passivation is an important process in the manufacturing of reliable laser diodes. It’s a method of treating the facet ends of a laser to prevent excessive heating during operation, which may destroy the laser. Specialized precision machinery is required, as the process needs to take place under extremely strict environmental conditions.

One of the most effective and time-tested facet passivation methods was developed by IBM Laser Enterprise in Zurich in the 1990s. Known as the “E2” process, it involves coating the facet with a thin layer of silicon right after it is cleaved, or separated, from the adjacent facet. This is done in a special chamber under ultra-high vacuum and very cold temperatures to prevent contamination. Achieving these conditions requires a molecular beam epitaxy (MBE) machine with several vacuum pumps and liquid nitrogen, and special tools are required to handle the lasers and deposit the coating.

Among many other applications, lasers passivated with the E2 process are used to amplify voice and data signals over fiber-optic cable, including about half of the world’s internet. Around 50,000 of these were installed in underseas, transcontinental cables in the 1990s, which must be reliable for over 30 years due to the difficulty in accessing and servicing these lasers. Similarly, over a million lasers were installed in terrestrial cables during that time. The accumulated field data has shown these E2-passivated lasers to be among the most robust and reliable ever produced; many of them were manufactured by a small US-based company called Lasertron.

Sheaumann Laser utilizes the E2 passivation process in all its single-mode diodes as well as its multimode diodes of 1W or higher. Sheaumann’s ownership also owned Lasertron in the 1990s, and several members of Sheaumann’s staff worked at Lasertron and were involved with the E2 technology transfer from IBM. The facet passivation process at Sheaumann is supported by rich history and extensive experience, giving Sheaumann’s customers a marketplace advantage with the enhanced reliability of their own products.

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