SMART Photonics proudly introduces HS64AC, our next-generation AlQ-based InP Photonics Design Platform, now available as PDK version 0.2.0.
Data Centers use 100’s of thousands of transceivers for all their fiber-optic connections.
It’s important because transceivers that are operated in Data Centers are exposed to higher and higher environmental temperatures. The reason for that is that the equipment in data centers produces an enormous amount of heat and this heat needs to be controlled.
Controlling a lot of heat by fans and AC takes a lot of energy and electricity. And for this reason it’s very advantageous if you can operate all the equipment, such as servers and switches, at a somewhat higher temperature. This will simply save power.
For this reason, optical transceivers in data centers are nowadays specified to operate uncooled (they have no Thermo Electric cooler in their package) up to 85°C.
Typically, semiconductor lasers such as DFB lasers and EMLs do not operate well at elevated temperatures. They will draw more current and can even suffer from thermal roll over. This happens when the device starts to self-heat because of the high current it needs, which takes it to even worse performance, which then demands more current… ending in a roll over with no light output anymore.
The solution is to look at the fundamental laser operation and see where we can make that more efficient. And when we zoom in those fundamentals, we see that we can actually solve the problem.
This problem is best described as follows: in a semiconductor laser, light is generated by recombination of electrons and holes. The more efficient this process is, the better your laser will be. Now, the material layer that accounts for this process is called the quantum well active layer. And what we see at elevated temperatures is that especially (thermally activated) electrons, escape from this layer before they recombine with a hole to generate light. And as said, the hotter, the more electrons “boil” over. You can compare this with a saucepan full of milk on a hot stove.
The trick is to make sure our “saucepan” gets deeper by making the “sidewalls” higher. This can be done by replacing the element phosphorus in the quantum well crystal with the element Aluminum.
This build up is schematically depicted in figure 2:
Figure 2 – Showing “deeper” quantum wells for electrons in the quantum well on the right hand side
At SMART Photonics we are now changing over our PDK platforms to “AlQ” which means that our lasers show better performance at elevated temperatures, for instance expecting to meet the 85°C harsh conditions in Data Centers and AI cluster environments, later this calendar year.
Figure 3 shows performance of two lasers that have identical geometries and build but that only differ in the Quantum well material: “PQ” versus “AlQ”
Figure 3: Light output versus injection current (L-I) graphs for two different material systems of our quantum well material. As can be seen, the blue curve has a much better efficiency and will perform well, even at 85°C, as soon as we have released the O-Band version later this year.
By changing the Quantum well material from PQ to AlQ, SMART Photonics now enables laser operation up to 55°C. We recently released a PDK called HS64AC 0.2.0, a C-Band based PDK that has this great feature built in. The O-band equivalent is expected soon, in Q4 2025.
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