Full Transcript
https://www.youtube.com/watch?v=9sDzucSzwQ4
[00:00] So um yeah welcome to Europe practices.
[00:04] So um yeah welcome to Europe practices webinar series on advanced packaging.
[00:07] Webinar series on advanced packaging.
[00:12] I'm Ramsey Salim and a neuro practice lead at International Institute where we focus on system integration and advanced photonics packaging.
[00:20] This webinar continues in our series where we step into the world of advanced photonics packaging.
[00:25] In the first couple of episodes we introduced the topic of advanced packaging and then looked at some of the packaging design rules that do's the don'ts and the common pitfalls.
[00:36] And in the next few episodes we're going to look at fiber to chip coupling the various techniques involved.
[00:45] And in today's episode we'll look particularly at edge coupling.
[00:47] But before we jump into it let's get familiar with the zoom platform and that we using today if you're not already familiar with it.
[00:57] And so there's a Q and a button if you have questions just click on the Q&A button.
[01:03] questions just click on the Q&A button and add your questions in there and.
[01:05] and add your questions in there and we'll collect the questions and answer.
[01:07] we'll collect the questions and answer them in a Q&A session after the talk but.
[01:11] them in a Q&A session after the talk but without any further delay let me.
[01:13] without any further delay let me introduce you to my co-hosts and.
[01:14] introduce you to my co-hosts and panelists we've got dr. Francesco Flores.
[01:16] panelists we've got dr. Francesco Flores head of the training programs and dr.
[01:18] head of the training programs and dr. Daniel Kerry in charge of the.
[01:20] Daniel Kerry in charge of the development of the laser welding at.
[01:21] development of the laser welding at Tyndall over to you Francesco thanks.
[01:25] Tyndall over to you Francesco thanks.
[01:29] thanks hi everybody so today we start.
[01:33] talking about how we can couple the.
[01:37] light in and out from our pika and there.
[01:40] are mainly two ways the first one is the.
[01:42] edge coupling while the second one is.
[01:45] the grating coupling today we will focus.
[01:47] on edge coupling in the next few.
[01:49] episodes we will talk deeply about.
[01:53] creating coupling so edge coupling the.
[01:55] main question is about the mod mismatch.
[01:58] that is actually the main issue that we.
[02:01] have to face to obtain a good coupling using the edge coupling then I will show.
[02:05] using the edge coupling then I will show you the main features and some standard.
[02:07] you the main features and some standard packages the most important one is.
[02:09] packages the most important one is called butterfly package then I will.
[02:12] called butterfly package then I will produce you two.
[02:13] produce you two mechanical design and then I will show.
[02:16] mechanical design and then I will show you the shape of a final design for a.
[02:20] you the shape of a final design for a device that is ready to be used and just.
[02:24] device that is ready to be used and just an intern two alternative ways to match.
[02:27] an intern two alternative ways to match the nodes one is to use an additional.
[02:30] the nodes one is to use an additional fiber before facing the pker and then.
[02:34] fiber before facing the pker and then what is called adiabatic tapering but.
[02:37] what is called adiabatic tapering but actually let's say modernistic.
[02:39] actually let's say modernistic okay it's important but let's say the.
[02:41] okay it's important but let's say the the fiber for us is a source so it's.
[02:45] the fiber for us is a source so it's mainly better to explain a little bit.
[02:48] mainly better to explain a little bit better and in detail the different types.
[02:51] better and in detail the different types of fibers that we can use yeah so um in.
[02:56] of fibers that we can use yeah so um in the last session and we mentioned fiber.
[02:59] the last session and we mentioned fiber and Francesco you kind of looked over it.
[03:02] and Francesco you kind of looked over it and introduced the fibers just kind of.
[03:04] and introduced the fibers just kind of refresh people's memory here with it.
[03:06] refresh people's memory here with it especially that we're looking at fiber.
[03:08] especially that we're looking at fiber to check coupling and so the most common.
[03:11] to check coupling and so the most common fiber is single-mode fiber it's the.
[03:14] fiber is single-mode fiber it's the backbone on the fiber optics Network it.
[03:16] backbone on the fiber optics Network it has a tight core allowing for about.
[03:19] has a tight core allowing for about eight to ten micron mode field diameter.
[03:21] eight to ten micron mode field diameter and it's surrounded by a 125 micron.
[03:25] and it's surrounded by a 125 micron diameter of cladding different slightly.
[03:28] diameter of cladding different slightly different index and then there's a.
[03:31] different index and then there's a coating layer light propagates along the.
[03:34] coating layer light propagates along the fiber in a single mode it uses total.
[03:37] fiber in a single mode it uses total internal reflection making it very.
[03:39] internal reflection making it very useful for a wide range of applications.
[03:42] useful for a wide range of applications and it can go for very long reaches use.
[03:45] and it can go for very long reaches use in applications where there's long reach.
[03:47] in applications where there's long reach and it's they like I said the most.
[03:49] and it's they like I said the most popular fiber other types of fiber that.
[03:54] popular fiber other types of fiber that are quite popular to include multimode.
[03:56] are quite popular to include multimode fiber so multimode fiber has a wider.
[03:59] fiber so multimode fiber has a wider core and that allows for multiple modes.
[04:02] core and that allows for multiple modes to propagate in the fiber using.
[04:04] to propagate in the fiber using refraction it has a higher bandwidth and.
[04:09] Refraction it has a higher bandwidth and it's popular in short to reach applications.
[04:11] Applications like in data centers another popular fiber is the polarization maintaining fiber.
[04:22] It's a specific type of single mode fiber and it has stressed core rods running through it that create a fast axis and the slow axis.
[04:34] The polarization maintaining fiber from its name it maintains the polarization inject it into it from the source so they don't swap from fast access to slow access or vice versa.
[04:50] Each each polarization sticks to its axis but that raises a question for me Francesco so if I'm using a single mode fiber how do I couple light to a silicon on insulator chip?
[05:04] Yeah okay that's a great question absolutely and it's a great question mainly because
[05:10] and it's a great question mainly because let's say the main features that we have
[05:14] let's say the main features that we have to overcome is the so-called modest
[05:16] to overcome is the so-called modest match these arise from the fact that has
[05:19] match these arise from the fact that has you explained the core of the fiber has
[05:21] you explained the core of the fiber has a diameter of your garage ten microns so
[05:24] a diameter of your garage ten microns so the mode field diameter that is the
[05:27] the mode field diameter that is the dimension and transversal dimension of
[05:29] dimension and transversal dimension of the motor running inside the core is of
[05:33] the motor running inside the core is of the order of 10 microns our web guides
[05:37] the order of 10 microns our web guides are instead characterized by dimension
[05:39] are instead characterized by dimension that are SOI thickness 220 nanometers
[05:43] that are SOI thickness 220 nanometers while the width is just from 450 to 500
[05:50] while the width is just from 450 to 500 nanometers so the main problem is we
[05:53] nanometers so the main problem is we have to reduce the mode field diameter
[05:55] have to reduce the mode field diameter of let's say two orders of magnitudes
[05:58] of let's say two orders of magnitudes and the second problem is if I have an
[06:01] and the second problem is if I have an Thunder fiber single mode fiber I have
[06:05] Thunder fiber single mode fiber I have no control on the polarization of the
[06:08] no control on the polarization of the electromagnetic States that is running
[06:10] electromagnetic States that is running inside its core so I can imagine that I
[06:13] inside its core so I can imagine that I have a polarization state that is has in
[06:16] have a polarization state that is has in this red arrow aligned in a certain way
[06:20] this red arrow aligned in a certain way but unfortunately is not aligned with
[06:24] but unfortunately is not aligned with respect to that work waveguide
[06:27] respect to that work waveguide polarization that is usually te so the
[06:30] polarization that is usually te so the main problem is a I have to reduce or
[06:35] main problem is a I have to reduce or adapt the mode field diameter B I have
[06:38] adapt the mode field diameter B I have to
[06:39] to the polarization state of the wet guide
[06:43] the polarization state of the wet guide with the core of the fiber if I am using
[06:48] with the core of the fiber if I am using a standard sy for example I have the
[06:53] a standard sy for example I have the problem that my edge coupling is
[06:55] problem that my edge coupling is polarization insensitive so in this case
[06:58] polarization insensitive so in this case I add for example to use an external
[07:01] I add for example to use an external device that must be able to select the
[07:05] device that must be able to select the specific polarization state that I need
[07:08] specific polarization state that I need or I can use a peon fiber in that case
[07:12] or I can use a peon fiber in that case the cost is higher it depends.
[07:15] the cost is higher it depends specifically on the application let's.
[07:17] specifically on the application let's say that to be clear for SOI we do not.
[07:21] say that to be clear for SOI we do not have a way to fix the polarization state.
[07:24] have a way to fix the polarization state the only thing that we can do is we can.
[07:28] the only thing that we can do is we can take for example the mode field diameter.
[07:29] take for example the mode field diameter that in the core of the fiber is 10 micron.
[07:32] we can let's say taper the edge the tip of the fiber in order to reduce.
[07:36] the tip of the fiber in order to reduce the lateral dimension and this is acting.
[07:40] the lateral dimension and this is acting as a lens in this way I can reduce the.
[07:43] as a lens in this way I can reduce the diameter of my beam in the region.
[07:47] diameter of my beam in the region between the tip of the fiber and esy.
[07:51] between the tip of the fiber and esy region that is called hotspot to 3 microns.
[07:55] region that is called hotspot to 3 microns I am reduced from 10 to 3 then I.
[07:58] microns I am reduced from 10 to 3 then I can use the so-called spot size converter.
[08:01] can use the so-called spot size converter the spot size converter.
[08:04] converter the spot size converter usually made of polymer is just a system.
[08:06] usually made of polymer is just a system with a transverse dimension of the order.
[08:09] with a transverse dimension of the order of 3 microns to me my con in order to.
[08:14] of 3 microns to me my con in order to match the lateral dimensions of the.
[08:17] match the lateral dimensions of the hotspot.
[08:18] hotspot I can collect the light with the spot.
[08:21] I can collect the light with the spot size converter then using again a.
[08:24] size converter then using again a tapered shape for the SOI waveguide I.
[08:27] tapered shape for the SOI waveguide I can inject the mode inside the waveguide.
[08:30] can inject the mode inside the waveguide and in the end I have the mode inside.
[08:34] and in the end I have the mode inside the waveguide but pay attention because.
[08:37] the waveguide but pay attention because since the expect ratio is 220 hi 450 the.
[08:42] since the expect ratio is 220 hi 450 the width for sure the polarization state of.
[08:45] width for sure the polarization state of the waveguide will be always te which.
[08:48] the waveguide will be always te which means that the electric field is.
[08:49] means that the electric field is oscillating horizontally.
[08:53] oscillating horizontally let's take an example in this case I.
[08:56] let's take an example in this case I want to talk about how to use H coupling.
[09:00] want to talk about how to use H coupling to collect the light ejected by a laser.
[09:04] to collect the light ejected by a laser cavity what we do is we put in place the.
[09:09] cavity what we do is we put in place the laser we connect the laser and we switch.
[09:11] laser we connect the laser and we switch on the laser so we have the light coming.
[09:14] on the laser so we have the light coming out from the cavity at this point you.
[09:16] out from the cavity at this point you see we just put in front of the laser.
[09:19] see we just put in front of the laser cavity how were properly tapered.
[09:22] cavity how were properly tapered waveguide so this shape again is also acting as a lens.
[09:26] waveguide so this shape again is also acting as a lens so we can collect the light.
[09:29] acting as a lens so we can collect the light and focus the light inside the center of the core or the fiber.
[09:33] light and focus the light inside the center of the core or the fiber in this way we are announcing the injection of the light inside the core.
[09:36] center of the core or the fiber in this way we are announcing the injection of the light inside the core.
[09:38] in this way we are announcing the injection of the light inside the core we are in this way optimizing the coupling efficiency.
[09:42] injection of the light inside the core we are in this way optimizing the coupling efficiency consider that.
[09:46] we are in this way optimizing the coupling efficiency consider that usually in this case we are low insertion losses.
[09:48] coupling efficiency consider that usually in this case we are low insertion losses we are talking about the 1 DB around 80 percent of transmission.
[09:50] usually in this case we are low insertion losses we are talking about the 1 DB around 80 percent of transmission.
[09:53] insertion losses we are talking about the 1 DB around 80 percent of transmission the main problem is that we have typed sensitivities.
[09:56] the 1 DB around 80 percent of transmission the main problem is that we have typed sensitivities so it's really harder and making these if you have question.
[10:00] transmission the main problem is that we have typed sensitivities so it's really harder and making these if you have question you can also ask Daniel.
[10:03] have typed sensitivities so it's really harder and making these if you have question you can also ask Daniel because it's the expert in this field.
[10:06] harder and making these if you have question you can also ask Daniel because it's the expert in this field it's really difficult.
[10:09] question you can also ask Daniel because it's the expert in this field it's really difficult it's really hard work to finally align the fiber in front of.
[10:11] it's the expert in this field it's really difficult it's really hard work to finally align the fiber in front of.
[10:14] really difficult it's really hard work to finally align the fiber in front of.
[10:19] to finally align the fiber in front of the laser usually tolerances up or the.
[10:23] the laser usually tolerances up or the order off from let's say 1 to 3 microns.
[10:27] order off from let's say 1 to 3 microns really tight tolerances but it's.
[10:31] really tight tolerances but it's interesting because in this case again.
[10:33] interesting because in this case again we are talking about packaging so we.
[10:35] we are talking about packaging so we have to be sure that we are dealing with.
[10:37] have to be sure that we are dealing with standards and standard means that we are.
[10:40] standards and standard means that we are sure that we can manage the packages we.
[10:45] sure that we can manage the packages we can manage the external boxes and we can.
[10:47] can manage the external boxes and we can work inside the boxes in order to put in.
[10:50] work inside the boxes in order to put in place all our devices as I already told.
[10:53] place all our devices as I already told you during the previous webinar the.
[10:56] you during the previous webinar the standard in this case is the so called.
[10:58] standard in this case is the so called butterfly package why it's so important.
[11:01] butterfly package why it's so important because we can use our claims in order.
[11:05] because we can use our claims in order to grab.
[11:06] to grab fiber or all the other devices and put.
[11:09] fiber or all the other devices and put them properly in place inside the.
[11:13] them properly in place inside the external box so we are sure that the.
[11:16] external box so we are sure that the final result will be the best that you.
[11:19] final result will be the best that you can obtain resorting to this technique.
[11:23] can obtain resorting to this technique.
[11:27] this is an example of a final device so I show you let's say the region of space
[11:31] that is highlighted by these two arrows
[11:35] here in red in this case the system is obviously a little bit more complicated
[11:40] say we have a ceramic interposers we have discrete electronics we have an electronic integrated circuit that we use to manipulate the signals that are coming from our beaker or we use the electronic integrated circuit to control our pixel and then what we have is here the edge coupling you can see the head of the fiber and in this case you can see then a standard single-mode optical fiber
[12:13] what is important again is consider the dimensions we are switching from something that is 200 micron by 200 micron by 100 microns to something that is of the order of centimeters
[12:25] is of the order of centimeters 3 centimeter cubes which means that we are
[12:27] centimeter cubes which means that we are talking about things that are order of
[12:31] talking about things that are order of magnitudes difference geometrically
[12:35] magnitudes difference geometrically speaking but in any case of things that
[12:37] speaking but in any case of things that remain really really small so it's
[12:41] remain really really small so it's fundamental to pay attention when you
[12:43] fundamental to pay attention when you are working on the alignment what we can
[12:47] are working on the alignment what we can do different with respect to what you
[12:49] do different with respect to what you are show you well let's say there are
[12:51] are show you well let's say there are techniques that we are also taking into
[12:53] techniques that we are also taking into account to be implemented inside our
[12:56] account to be implemented inside our standards in in your practice and one of
[12:59] standards in in your practice and one of these alternatives is to use an
[13:01] these alternatives is to use an additional fiber so instead of using
[13:03] additional fiber so instead of using just a single mode fiber with a mode
[13:05] just a single mode fiber with a mode field diameter of 10 microns here in
[13:08] field diameter of 10 microns here in this case an SMA 28 we can use a uhm a 7
[13:13] this case an SMA 28 we can use a uhm a 7 that is another fiber with a core that
[13:17] that is another fiber with a core that is of the order in the diameter of
[13:20] is of the order in the diameter of to dine in microns in this way we can
[13:23] to dine in microns in this way we can immediately on the other side match the
[13:28] immediately on the other side match the mode of the spot size converter it's mode of the spot size converter it's easier and let's say depending on the specific application can be better than facing directly the SMF in front of the spot size converter another interesting application is the so called adiabatic tapering this is a option technique that it's really well established in electronica so we are just creating an optical interposer so what we are doing is just a system that we interpose between the fibre on the right so this side of the interposer is matching the mode of the fibre ten microns on the other side we have reduced the dimension of the mode and we have the so-called peak matching so the mode field diameter on the left side of this adiabatic tapering is reduced to three microns instead of using the uhm a7 we are using
[14:31] instead of using the uhm a7 we are using the aromatic taper angle another option.
[14:35] the aromatic taper angle another option so Ramsey I hope it was quite clear yes.
[14:40] so Ramsey I hope it was quite clear yes that's very interesting Francesco I've got a few questions myself actually.
[14:45] got a few questions myself actually but before we jump into the Q&A session.
[14:47] but before we jump into the Q&A session let me just tell you all a bit about what's coming up in this webinar series.
[14:52] what's coming up in this webinar series so it's a series with multiple episodes.
[14:55] so it's a series with multiple episodes and we're just getting warmed up with these last sessions.
[15:01] these last sessions Tyndale is a global leader in advanced photonics packaging and has great greatly kind of contributed to the field.
[15:10] greatly kind of contributed to the field especially in grating couplers so in their design there are various types how to optimize them and when to use each type.
[15:20] to optimize them and when to use each type and the next four episodes will be focusing on grating couplers and looking at them in detail.
[15:30] and looking at them in detail and this is just kind of the introduction into that and so.
[15:33] of the introduction into that and so the next episode before I jump into questions is in two weeks times fifth of May and we'll be looking at a fiber to chip coupling using grating couplers and