I would also love to have Suresh explain PL. I have been really busy lately with family business but I have been trying to spend some time to better understand the steps associated with POETs optical interposer platform because it is not clear and maybe there is a reason for that.

The POET platform combines both heterogeneous and hybrid integration. So it kind of takes the best of both worlds and applies them in a complimentary way.

Building the best active optical devices requires III-V epitaxy so the best means separate III-V chips in GaAs or InP material sets so long as there is an efficient way to  connect the optical  and electronic circuits. And for POET as I understand it that Multi Module Chip Set which is the optical engine includes III-V dies with III-V waveguides which connect to  mode matched dielectric waveguides so that the losses are lowest that can be achieved through high speed lithography as part of the CMOS process.

And in the case of POET the dielectric wave guide is athermal meaning that the wavelength has a very minimal shift across the operating temperature range which means less temperature control  is  required and dense packing of the waveguides for MUX/DEMUX across multiple wavelength are not  impacted by thermal cross talk. And since the active dies that contain the lasers which by their nature generate heat are isolated from both the electronics and the waveguides by the geometry that POET has devised there is the ability to heat sink efficiently without impacting the temperature of the waveguides. And all of this  happens in the smallest footprint possible.

So the heterogeneous aspect is related only to the dielectric and the passive elements are produced with high precision after the fact for extremely accurate mode matching. It is something that industry has tried to do for a long time and POET has found a way to do this using the dielectric.

Which is why big companies want them to design optical engines for them.

I did a search of Rockley’s patents and as far as I can tell they don’t have an optical interposer or a waveguide technology that does what POET is doing.

POETs waveguides have a high level of refractive control and geometry without any free space optics which is at the heart of the POET platform.

Does it mean that Rockley does not have the same level of efficiency? I honestly don’t know but it would actually surprise me if they did. It is a big problem and a big market and there will probably be a number of solutions with varying degrees of technical advantage.