MicroVCSELs vs MicroLEDs, a MicroExplainer

0:00Credo bought Hyperloom, a micro LED interconnect startup. Then at OCP this week, Credo's first active light cable turned out to use micro Vixels. Why buy one technology and pick the other for your first product? The bigger question is how we connect AI systems. Do we keep pushing each lane of light faster or spread the data across hundreds of slow ones? And if we spread it out, LEDs or Vixels? Austin and I are going to explain both and who's building them. Let's get into it.

0:35Hello, listeners, and welcome to another episode of Semi-Doped. I'm Austin Lyons of ChipStrat. I write a newsletter for institutional investors and tech executives, and I also consult with semiconductor companies. Hey, I'm Vic Shaker, and I write Vic's newsletter on Substack, and I'm the founder of Semi-Exponent, a boutique research firm on semis. How's it going, Austin? Hey, man, it's going well. just got back from OCP. Where are you at? I am still in San Jose in a friend's garage. I actually fly out to Japan today, purely out of holiday reasons. This is not for semiconductors. I'm not hunting Japanese company Alpha.

1:12I'm not doing any of that stuff. We have great people already working on that. I'm literally going to go check out Japan for a week with my family on the way back because it's kind of on my way back to India. And so we're recording this before I hop on the flight. But yeah, this is post-OCP. It was an insane show. There were so many people that they had to close down the registration and people were buying entrance tickets on the black market. And the halls were overcrowded and the exhibition halls were full. Very exciting show. Yes, yes, it was something. And I had a ton of fun talking to people on the show floor, talking to people outside.

2:00A lot of people ran into both you and I since we were there together and said, hey, we listen to the pod. So thank you, people who listen. It was fun to see you. I honestly didn't sit in that many talks. I sat in some, but it was there's just so many people to talk to, so much to see. And also the talks that were being put on YouTube. So I thought, yeah, I can watch them later when I get home at 2X, you know. yeah if you go to the open compute project youtube website you'll see all the talks there uh totally free to watch i think it's amazing that they did that pretty much on the same day it it avoided a lot of fomo for the people who were there and uh people like us decided let's talk to more people let's visit the show floor because they have wheeled in so much equipment and if nobody sees that it's kind of a tragedy and so we spent a lot of time on the show floor talking to people.

2:50And that was so much fun. Now I have all the YouTube videos as as everybody else. And so we can go and watch it at our leisure, at our correct pacing, whatever. Right. Totally. Totally. Which I do have some time blocked next week to catch up on them because there was there were so many good talks. OCP did a good job. Couldn't get through them all. But one big talk in the topic for today, we're going to do a micro explainer on micro emitters. So micro LEDs or micro vixels or both lots of micro to talk through um so that was really the talk of the show bill brennan ceo of krino had a keynote very early on i think it was on the very first day and um it was surprising uh so let's just dive into maybe let's dive into the credo news but then we'll zoom out and talk about micro emitters micro leds micro vixels and everything but yeah Do you want to give us the news first and then we can zoom out?

3:49The whole stir up happened on the conference show floor where everybody's like, oh, did you catch that talk by Bill Brennan radio? And I was like, oh, wait, I was watching this stuff over here. But luckily, you know, the YouTube videos helped. I watched it immediately as soon as it was posted. So the whole thing was the background is that for the longest time, we've been thinking that micro LEDs are going to be the way that cables are made. with light because copper is kind of reaching its limits and what it can do in terms of reach at a given speed. Optics has its like pros and cons. It's expensive.

4:27It's power hungry, all of that stuff. So there's always this middle ground where it's a battleground for what kind of technology has to go in. And for the longest time, a lot of people were working on micro LEDs. And these LEDs are pretty much like a light bulb in the ceiling, but you know, it's pretty much a small condensed version of it and there are many companies working on this avicena credo acquired a company called hyperloom for 92 million with this technology microsoft was working with mediatek i believe on what they call project mosaic and marvel was working with this company called mojo vision to develop micro led so all of these companies are like artificial reality uh vr ar vr companies who had these micro led technologies already in production and they were like okay let's pivot to data centers because there's so much money to be made so there was all this talk but then what happened at the talk at ocp is that everybody thought this is going to be micro leds or at least i did maybe everybody didn't yeah but he got on stage and said yeah we were doing micro leds but we decided we'll just do micro vixels for the sake of reach and this sparked in everybody's mind the feeling that okay micro vixels as a technology is the future and micro leds are kind of no more that is the sentiment on the show floor but i think there's a lot more than that i don't know how much of it we'll be able to get into it's really a long discussions.

6:04I plan to write an article on that as well. But yeah, let's at least cover the basics of what these things are. Why are we talking about these micro emitters? What are the differences between micro LEDs and micro pixels? And how to think of this going forward? Yes, yes, sounds good. I agree. Also, everyone was basically like, what are micro LEDs dead? You know, that's like when we saw people that came right from that, like, I guess it's micro pixels now. But, you know, maybe also focus on Credo really quick, and then we'll get into the specific technologies. You know, anyone who's been following Credo, obviously there's this whole conversation over the past year of, you know, is it electrical?

6:42Is it optics? And Credo was the first to come out with the AEC, the active electrical cable, which was as we continue to talk at higher and higher speeds, the reach of copper shrinks. And Credo said, hey, if we essentially put some digital processing on both ends and throw a little bit of power in there, we can extend the reach of copper. And, uh, but still there's, as you look forward on the roadmap, um, the question is, you know, how long will a ECs last? And, and there's long range, uh, communication over optics using very powerful lasers, for example, but this kind of like medium reach, there's a question in like the portfolio gap of passive copper, AECs, maybe something else, ALCs, active light coppers or or active light cables, and then, you know, your traditional longer reach optics.

7:32And in this sort of intermediate area is where people were expecting Credo to come out and have these ALCs driven by micro LEDs. But then yes, the talk was about like, hey, we learned a lot from micro LEDs and actually micro Vixels are a good fit here. So that's again, the framing, but now let's get into it. So maybe start us with micro LEDs. And then, of course, I want to go into micro Vixels because people probably heard a little bit of micro LEDs over the past, but not as much about micro Vixels. Although, you know, we have had a conversation with Al Yoon of PicoJewel, which was helpful and people can listen to that as well.

8:09But yeah, let's dive into micro LEDs. Sounds good. I want to set the basis for what these are called micro emitters. And essentially, like you mentioned there's a reach gap but i just wanted to mention one other thing about why this reach gap is important now because obviously lasers indium phosphide based lasers can go a long way and i want to mention why this material matters because indium phosphide is in short supply and everybody like you know is scrambling to make this happen because optics is becoming a big thing in ai but yeah indium phosphide optics can go you know thousands of kilometers if you have to you know but we don't need all of that for the data center and the point is that why do you use a technology that is a in short supply be capable of a lot more when you don't need it can we use the right technology for the right application copper beyond seven meters at you know to 224 gig uh is about you know like already pushing it pam six uh which is a new modulation scheme is being considered to extend the reach of copper so the copper work is going on on one side but it's becoming very difficult optics is like an overkill technology with indium phosphate so there is a reach of between say five meters and 50 meters where there's a lot of applications you could do other things and this is important because now it's becoming way more important to expand the number of gpus in the scale up domain and it is becoming too hard to put too many GPUs in a rack.

9:39So even at, you know, we were at the keynote from NVIDIA at OCP and Ian Buck showed the picture of like eight Oberon racks connected together in NVL 576. And of course that picture showed that it was co-packaged optics hooking them all up together. So that's NVIDIA solution. But everybody need not have to use co-packaged optics or near package optics. You Instead, there is a way to connect these things with other forms of light. And so 50 meters is enough to connect a lot of this stuff. And the question is, what is that technology? That brings us to micro emitters. So this is what the industry has been working on.

10:17And I'd say that although micro Vixels have been, micro Vixels, Vixels, I don't want to differentiate too much, but here for the sake of the micro aspect of it, we'll just call it micro Vixels, have been around a very long time. right like Vixels have been used in data centers that's one thing to remember about it and we'll cover more about this but micro LEDs and we should enter into talking about micro LEDs now is that it is a far newer technology for interconnects it has not been deployed in data communication applications like long you know LEDs have been in displays and all of that stuff but for communications it's not has it hasn't been a mainstay whereas Vixels have been a mainstay of communication systems for a long time before we went to single mode optics, right?

11:03But you know, Vixels have been around, they have been deployed, they do work at scale, with limitations, but they work. This episode of Semi-Doped is presented by Crusoe. They build the power, the data centers, and the cloud behind AI. Did you know Crusoe can help you tune an open source model on your own data for just a few bucks? Frontier models are very good, but they don't know your company's terminology, your part numbers, or how you like your reports formatted. So you keep stuffing instructions and context into the prompt of an expensive frontier model to get the job done. But for simple repeatable work like reports, an open source model trained on your data can actually match a much bigger model.

11:45Think of a new grad with three months of on-the-job training. You don't always need the PhD. And the open model is cheaper and faster to run. Fine-tuning used to mean renting GPUs, working on orchestration and Kubernetes, writing training code, and babysitting the entire setup process. But Crusoe's serverless fine-tuning removes all of that. Upload your datasets, pick an open model like GLM, Lama, or DeepSeq, and they handle the training. You pay per million token used, not per GPU hour. And on the smaller models like QN38B,$2 can take you a long way with millions of training tokens available.

12:24Once the training is done, you can then deploy them on Crusoe Cloud in just one click or download the weights and run them anywhere. Your data only fine-tunes your model. And it doesn't have to be work data either. You can try it on how you write emails. Pick a task, compare the tuned model to your current prompt, and see how it does. Crusoe's giving all new accounts$5 in credit to get started today. That's enough to start tinkering with fine tuning right now. Links in the description. So micro LED. So let's talk about this new incumbent technology, the new technology that wants to displace optics.

13:03So essentially what it is, is that it's literally a diode. If anybody has done a basic electronics course, it's just like a p-type semiconductor with an n-type semiconductor. It is made out of gallium nitride and it emits light approximately in the 420 nanometer range, which is actually blue light. And you can see it in these interconnects that like, you know, if you look at the place where the micro LEDs are, you can see blue light being emitted. So it is blue LEDs that are doing this. You have red LEDs, you have green LEDs, anyway. So a lot of the work around micro LEDs has been at 420 nanometers.

13:45And the thing with micro LED light itself is that it emits light based on what is called spontaneous emission, which means the moment you apply a little bit of voltage to this diode, it turns on. I mean, like it doesn't have like a threshold voltage, like the minimum voltage after which it turns on. it's like a continuously varying thing it's like the dimmer switch in your in your wall right the moment you start raising the dimmer switch you know you don't have to like push it 75 percent of the way up to for it to even turn on okay this is an important analogy to remember because we need to use the same framing when we get to uh talking about vixels but leds just turn on as you increase the light you know this just like you're used to at home so what ends up happening is that this is a different form of light emission called spontaneous emission where it's just like sending out photons randomly and they're not very correlated to each other this photon decides to leave at this moment in time the next photon decides to leave whenever it wants in time they're not like coordinated they don't march together they don't do anything like that just leave and then what are the other thing is this just like a like an led in your home right this light is very very broad angle light you know it's not like a pencil beam of light that you can use as a laser pointer you know that is a pencil being applied but leds are like dispersive they give a wide angle okay and so the the third feature feature or bug i don't know of micro leds is that they don't have a very good line width so if you look at it on a on a spectrum around 420 nanometers they're a pretty broad spectrum and so this is important because as this broad spectrum from light goes along an optical fiber, it faces what is called chromatic dispersion.

15:37And I know this is a lot of terms, but we have to cover these things. Yeah, yeah. Let me jump in here. So if it's supposed to be centered around 420 nanometers, when you say there's like a broad dispersion, you're saying some come out at 416 nanometer wavelength and some come out at 422 nanometer wavelength. So that's what you're talking about here. So the light coming out has different wavelengths. Yeah, that's what line width is. So ideally, you want, if you draw the wavelengths of a light source, you know, across wavelengths, you want it to be like a single line. You don't want like half a light bulb shape, you know, dispersion of like wavelengths.

16:16You can't have everything from 400 to 440 or something like that, which is approximately the bandwidth of this light source. It's about 10%, I would say. So you have anything from 400 to 440. So this is what results in chromatic dispersion. And let's get into quickly what that means. Chromatic means, you know, color, right? Dispersion means kind of how they scatter or something, right? Dispersed. So what happens is if you send 400 nanometers down an optical fiber, it takes, I don't know, let's say one second, okay? now 440 nanometers should also take one second so that they all arrive together right all the wavelengths should arrive together only then will you know it look like the same thing has arrived at the other end but it doesn't you know different wavelengths travel different speeds so what happens is like all these different wavelengths arrive at different times and when that happens you know when you send a pulse that pulse has basically spread out in time which means that you can't send pulses fast enough because now they start to overlap.

17:24So when you can't send pulses fast enough because they start to overlap at the other end, that means you're data rate limited. You can't send data fast enough. You can't keep sending bits because they're going to start overlapping. So you can only send bits slow enough so that you can still account for overlap at the end of the cable. Gotcha, gotcha. So if you have a very precise line width, it's a lot easier to make sense of the signal once it propagates down uh the wave guide or whatever but if your wavelengths are spread out then they kind of smear and maybe overlap and by the time it gets to the end of the wave guide it's harder to tell was this a one or a zero and and to your point um then you can't send signals quite as close together which ultimately means you can't send information is fast enough, right?

18:14So I'm assuming that you're leading us to say that the problem with LEDs is that they can't be used fast enough. Maybe that's like the problem for data centers. Yes. So it's a combination of speed and reach. So you see chromatic dispersion limits how much spreading happens. The further you send the signal, the more the spreading. So if you want to limit spreading one way to limit it is that you use it only for like i don't know five meters for example right and then the spreading is limited so you can send a reasonably high data rate now if you're going to keep it like 400 meters it's going to spread so much that your data rate you can't send data fast enough they're going to overlap right yeah is that spreading let me ask you really quick is the spreading a function a function of distance because the photons are just bumping into like the wave guide or something like why does it yeah it will spread more the longer you go because think about um you know like if two cars are racing right like a drag race for example um two cars like arrive they go a short distance in a drag race but the cars like are literally like i don't know microseconds or milliseconds of each other in a drag race right yeah but uh to think about like um a cross-country race that happens for 24 hour cross-country or something yeah yeah yeah um you have the cars coming at much more different time intervals you know the leader might come in first just the other the next car might come in like 10 seconds later one minute later things like that got it it's the same thing or you could think of this as a person running on a track like the the 100 meter dash has like extremely close timing But, you know, the 400 meter will have different spacings of people and the marathon will have even more space.

20:09Yes. Yep. Got it. Thank you. Carry on. The other thing is that micro LEDs, fundamentally, you can't turn them on and off fast enough to send data fast enough. This is a fundamental problem of the device. And right now we can only send about, I don't know, maybe three to five gigabit per second on a cable of like, I don't know, five meter reach, right? I mean, the LEDs can only turn on and off so quickly that you can send like five gigabit per second. So it's limited in both directions, right? The LEDs can't go faster inherently and they don't have reach. So both ways. So if they can only go three or five gigabits per second, but we're talking about a single lane wanting to, you know, first it was 50G, then 100G and now 200G, and then eventually we want to go to 400G.

21:02How do you get 224 gigabits per second if an individual LED can only send at like three gigabits per second? So you have to bundle a lot of K-fibers together. So you send many, many parallel lanes. For example, if you bundle about 300 of them together, you get a one terabit per second lane. I've written a very detailed post on all of this stuff when I visited Avicenna's office. We looked at the cables, we looked at the data that's being sent. So check that out on my Substack. I also have a full free article on Substack where I discuss this line width trade-off in micro LEDs and compare them to how lasers look, for example.

21:42That's completely free. So if anybody wants to check that out yeah but essentially to if you have such a slow data rate you have to now put you know multiple parallel highway lanes together and you have to put 300 of them a thousand of them if you want to do both directions or one direction or what speed you want you know you just have to double up the lanes and people don't really like that approach because because it gets complicated to couple like maybe 300 emitters micro LEDs into the cable. I mean, it's doable. It's not like it's not doable. You have to put a lens to focus because remember I told you the light was like dispersive everywhere.

22:23Like it just like fans out everywhere. So you've got to put a lens to focus it and make sure it goes into the fiber. Then you've got to have a lot of fibers. It's not an impossible task. The question is, do we really need so many lanes? Like, what if we can do it without having so many lanes? What if we could use a technology that actually had reach? What if we use a technology that could modulate data at a rate higher than 3 or 5 Gbps? Like, you know, that is what brings us to micro VIXELs. Okay, so what are micro VIXELs? So VIXEL is a way that people say it, but it's actually an acronym. it says v c s e l okay so that's vertical cavity surface emitting laser okay so the l is a laser so remember this is a laser this is not an led okay so it's not surface emitting led no it's surface emitting laser so so it's a so it's vertical cavity so instead of a lot of the optics that you know in silicon photonics and all that stuff that people talk about it actually emits from the side of the chip.

23:33So vertical cavity means that the cavity is vertical and the light is emitting vertically. And our podcast with Al, Al explains very nicely how all of this works. And he has like a prop too in that episode. So people should check that out. Definitely if you're listening to MicroVixels, because you will learn a lot from an expert on the subject. So that's definitely an episode worth checking out. But let's talk about this technology. So Vixels are made out of gallium arsenide. Okay. So it's not indium phosphide. It's not gallium nitride, but it's gallium arsenide. And Vixels are quite commonly used in like a lot of stuff.

24:16Like I think face ID is one example. And, you know, those are like basically like LiDAR, you know, like radar with light kind of thing. But they just shine light on your face and they kind of identify you. that's how it works so there's like a big supply chain for vixels because you know we put them in billions of phones already which is another benefit right like i told you like this has been used already in data communications also the supply chain is enormous and on top of that it uses gallium arsenide which has been a mainstay technology in like cell phones like every amplifier transmit amplifier called the power amplifier in your phone is built out of gallium arsenide okay so this technology is like like widely available the material supply chain is amazing you can build them on eight inch wafers so it's not like like indium phosphate you're limited to like three inch and now people are struggling to get to six inch no but this you can build an eight inch already so gallium arsenide is like widely available so vixels are widely deployed in both communications and in phones and in lidar so it's like wait so can we use this technology instead?

25:24Like, why don't we use this technology? Right. Got it. Got it. So, okay. On the one side, we started with, you have traditional indium phosphide lasers and, um, you know, there's a lot of struggle manufacturing those. Uh, and on top of it, they're very powerful. And if you're just sending light, even though it's high speed, you're just sending it, you know, short distance between GPU racks, let's say it feels like it could be overkill. And then on top of that, you know, maybe you're going down the route of co-package optics or near package optics. So there's concerns about maintenance as opposed to just a traditional pluggable cable.

25:59On the other end, you know, you said, oh, well, we could use all these micro LEDs and, but now we're going to take like a 200 gig signal. We're going to have to have some sort of gearbox to split it down into being able to send, you know, hundreds of three gigabit per second lanes. And so there's a little bit of, it's a little bit of circuitry needed there and a little bit of complication. But then on top of it, now we have like hundreds of fibers that we have to align to these hundreds of LEDs and they can't go quite as fast. And so, you know, you can start to see some manufacturing tradeoffs there.

26:31But you're saying micro pixels are kind of land in between. It's still the laser technology and it probably has a better line width and it can communicate faster as we'll get into. but at the same time that also unlocks the ability to not need to have so like hundreds of fibers presumably so is that where microvixel lands is somewhere kind of in the middle yes so microvixel is in the middle it's between micro leds and indium phosphide lasers so the reach can go i think the publicized reach at least now is 50 meters right like so it can go 50 meters and it can do data rates of 50 gigabit per second easily so it can do 10 times a micro led like data rates it can do easily it can probably do 100 gigabit per second it can probably do 200 gigabit per second like people are talking about doing that stuff although it's very difficult um because it has inherent limitations on how it works but it can do 50 and if you look at a lot of the demonstrations actually that people, there are other startups working on this too.

27:41It's not just Credo or someone else, but yeah, there are lots of companies working on this, but they all run it at like 25 or 26 or something. You don't even have to run it at its capability and that has its benefits. So maybe I don't go into that immediately, but it helps to run it slow. And I'll contrast why this is later. But essentially you can choose the wavelength of this to be either 850 nanometer, which is the widely deployed wavelength in all of like communications like 850 nanometer pixels are well known well studied okay then recently there's been a lot of talk about uh 1060 nanometer pixels which is what you can see from lumentum coherent all of these companies um are working on 1060 it has its benefits let's not get into the details of like what wavelength is better that's going to be for my substack but essentially you have a couple of wavelengths that are like higher in frequency right this is like infrared this is not blue 420 nanometers blue this is infrared so here you can modulate faster the reach is faster so what that means is to get like a one terabit per second 1.60 cable you'll have to put fewer fibers because you can run each one at at least five times as fast.

29:01Instead of five, you run it at 25. And then you can probably use five times lesser cables to get the same optical fibers, to get the same speed. So that's good in a lot of ways, right? Like, you know, it's simpler and you have a lot of design flexibility and it really solves the reach up to 50 meters. You don't get limited by five meters, 10 meters. Like you mentioned in the beginning of the episode, active electrical cables already can get to us in about seven meters reach with some tricks and all of that. So the question is, why don't we just go for reach? And so that's Credo's argument. They're like, let's just go for reach.

29:40I want a technology that takes me to 50, not to 10. Seven to 10 isn't enough to build up a product line. So we abandon micro LEDs. We're just going to go to Vixels. And so we get 50 meter reach. Yes. And I will say one thing that stuck out to me about what Bill Brennan said was they can still get the same reliability. Even though these are lasers and everyone has concerns about reliability, Credo can unlock the similar reliability as copper because they're already making an array of these micro emitters. And hey, if you're gonna use, let's say, you know, 50 of them, why not have like 55 of them in there and have some spares?

30:23So if one emitter were to fail, you could still have some extra fibers and some extra emitters and kind of on the fly. Always make sure that you have enough working emitters to be able to send the information. Yeah, this is a feature that is common to both micro LEDs and micro pixels. If you have parallel lanes, why don't you put like a few spare lanes and you could always switch over to the spare lanes? This is not really a feature that is specific to micro pixels. Sure, totally. It's wide, but slow. And this is the whole concept of the micro emitters. We are going wide, going many lanes, but slow.

30:59We are not going, you know, 200 gigs per lane, like an indium phosphide laser. We are going slow. We are going 25. We are going 50. Or we are going even 5 or 3, like, you know, micro LEDs. So whatever it is, this is slow, but we are using many lanes. And when you're using many lanes, you can always have spares. So this is not a unique feature, but it's nice. Yeah, it's a nice feature of wide and slow overall. Totally. And then I guess the difference with microvixels is you could increase this reliability from seven meters all the way to 50 meters. Yeah, yeah, yeah, exactly. And that's a good thing, right?

31:32Like you get like a whole new domain of interconnect that does not use indium phosphide, but solves a lot of problems. So futuristically speaking, it seems like that's a better product option to build. And the fundamental reason I have to bring back one analogy I use, you know, I use the dimmer switch analogy. the reason that the micro vixels can actually do a lot more than micro leds is that in this scenario when you increase the voltage to a vixel it doesn't emit any light i mean it does very very weakly but you know it doesn't really emit any light till you like bring it up to like at least halfway through you know and then bam you've got an explosion of light all right that is the the called stimulated emission of lasers, as opposed to spontaneous emission in micro LEDs, right?

32:21So stimulated emission means that all the photons now are in phase, like holding hands and marching like in a military regimen, like forward and the line width is narrow because all of these photons have a purpose. They're just like marching, right? So you've got on the line width, the spectrum of wavelengths, pixels are like narrower line widths and they're not as wide as micro LEDs and so the same chromatic dispersion argument applies here because now your narrower line width will take your signal further before it spreads out it still spreads chromatic dispersion happens to every form of light every everything right but it happens it only at a longer distance because the line width is narrow So it has like more room to spread before the bits start to overlap.

33:10Gotcha, gotcha. So you have stimulated emission, a tighter line width, which means you can send information further. And already you can send information faster than you could with LEDs. And yet, by the way, to your point, this is gallium arsenide. So an abundant supply. And it's still a pluggable form factor. So, right, we're not talking about NPO or CPO. This is just a cable that you plug in on both ends. With Credo, yes, but there is plenty of talk about using micro Vixels for NPO, as we saw at the Asterra booth. So those kinds of things are in discussion, and there were some nice things we saw at the show floor.

33:52But all of that is coming, yes. But even now, I think, you know, we are pretty early in the whole Vixel for interconnecting because even Credo's boot did not actually have a cable that was like showing electrical data on micro Vixels. They had some micro LED stuff. But so the switchover, I feel, is like very recent. And there's a lot of work to be done. And there is going to be a lot more stuff. I don't think that we are done with micro LEDs or it's dead or anything like that, because that's why even Credo has formulated it as a micro emitter. That's the broad technology. There are still use cases for micro LEDs, you know, and the industry is still exploring them.

34:41But yeah, essentially, they launched a work stream inside OCP called the Short Reach Micro Emitter Optics. So it's SRMO work stream. So the whole point of this is like a bunch of companies are getting together to talk about how to do short-reach micro-emitter optics. So there's a lot of stuff that's going to happen. This is not in any way settled. But I think the industry has, at least for the near term, chosen a part of micro-vixels. It seems that way, at least. Okay, okay. So micro-emitters is broad for, it could be micro-vixels, it could be micro LEDs, but you're saying it's going to be in the near term, it's going to be micro Vixels because of all the benefits we discussed.

35:25It can reach, you know, 50 meters, it'll be pluggables first is the pragmatic thing, but the same technology can be used for near packaged and for co-packaged. And we'll probably work our way there. I guess then lastly, what will we see micro LEDs anywhere? And if so, where will we see them? micro leds are still good for one fundamental reason that i think a lot of the discussion misses is that they are extremely uh heat insensitive gallium nitrite is what they call a high band gap semiconductor which means that they the operation of the light source is very insensitive to insensitive to temperature and that's important in some applications i would think one of those applications is scale in where you use optics within the tray the reach is not going to be i don't know like meters right like a tray the server tray is only this bag this big like about a few feet and within that is a very hot environment it's very difficult to replace anything that goes bad there so you want a very high reliability source of light i don't know the reliability numbers per se, but gallium nitride is in general a much better suited technology for something like that.

36:45Gotcha. So it has a high band gap. So even if it's in a very harsh, hot environment, like chip to chip or die to die, where you're just in the server and it's just kind of always hot, the heat isn't going to cause electrons to have all this extra energy and jump the band gap and start to like cause light to be emitted, right? There's the high band gap is like, oh sure, there's extra heat, but the molecules inside this particular diode are not, it doesn't cause the LED to turn on, so to speak. Right, right. So that's the whole thing. So it's high band. I have a whole article on what band gap actually means on the substack as well.

37:29So go look at that if you want to understand what band gap is. show notes yeah yeah yeah link it uh and then we can um you know because yeah what you're explaining is right if you have a high band gap then heat cannot cause electrons to switch states and emit light that's the broad explanation but that is an advantage and i don't think we are done with this technology yet i think we're still going to continue looking at it that's my that's my broad take although a lot of uh excitement is currently there around microvixels for good reason as we all as we discussed here right got it all right man well i think this was a good micro explainer on micro emitters from micro leds to micro pixels uh and with that uh any closing thoughts or should we just call it here uh no this is good enough for this episode because there's like a lot more to come uh we spoke to several exciting builders in this space uh and we would rather have them come on the podcast to talk about all these technologies.

38:34We spoke to people who are all willing to come on SemiDoped, thankfully, who are building the light stuff, the chip stuff. And so we have so much exciting content planned after OCP. Yes, love it. So we gave you the introduction here and we'll bring the experts on and let them take it one level deeper. So with that, people, thank you for listening to SemiDoped. like it, subscribe it, share it with people. We appreciate all your comments and we'll catch you next time.