What's inside a laser diode?

Рет қаралды 98,745

3 ай бұрын

Safety warning: definitely don't look at a laser with your eyes. Always wear laser glasses to protect your eyes, especially when working with lasers that emit light outside of the visible-to-humans spectrum. My phone was always in-between the laser and my eyes during the filming of this video, and I never put my eyes up to the microscope while the laser was underneath it.
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I removed this is the laser diode from an HFCT 5205A fiber optic transceiver . Here you can see that the laser module is made up of two main parts, the laser diode and a photodiode mounted behind it. To my knowledge, the photodiode here is used to tune the output of the laser diode.
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Like I stated in the video, I'm not 100% sure we are seeing just the laser in this video. The laser should emit at 1300nm, but my phone can still see it. My phone can see IR light, bit I don't know how big the wavelength can get before it doesn't see anything. This could be light before the the laser actually starts lasering, I just can't say for sure. I was also surprised that the light exited from the location that it did, but if I knew more about laser diodes, maybe it would make more sense.
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The Wikipedia page on lasers has a lot of good information and links to further reading material, much of which goes right over my head 😅

Пікірлер: 89

@michaelmcdonald4869 3 ай бұрын

From what I remember from my lectures, the reason there isn't a hole that the light is coming from is because the light is coming from energy being released from electrons moving in the PN junctions of the material. So it was just designed to release that energy at that spot

@adonian 3 ай бұрын

That’s cool info.

@EvilmonkeyzDesignz 3 ай бұрын

That definitely sounds correct, and it makes sense because I can't see the PN junction with my microscope, which gives the illusion that it's "coming out of nowhere". I'll have to do some more reading about diode lasers. :)

@dtiydr 2 ай бұрын

Also little quantum mechanics involved that can't 100% be explained.

@CloroxBleach0 2 ай бұрын

So what you’re saying is that design doesn’t require a mirror lens sandwhich like the one you’d find in a typical laser?

@michaelmcdonald4869 2 ай бұрын

@CloroxBleach0 So it's a similar idea, but on a scale of micrometers. You have your PN junction made of semiconductor materials, and an air gap junction between the PN junction. As you pump energy into the PN junction, electrons release and collide with holes and release energy. This process just keeps happening-converting electron energy into photons, with the photons bouncing between the PN junction, until it eventually exits the air gap junction and is emitted as light.

@Xsiondu 3 ай бұрын

That is so so so unsettling. Photons just leaving the metal like that. With old incandescent lamps i could trick myself into thinking the filament was just burning but not oxidizing. This however.... It's as of light just suddenly started coming out of a penny to me.

@wilurbean 3 ай бұрын

The heat to light is more quantum mechanic-y than a diode. High energy electrons recombine with positive charges inside the silicon diode. When the charges recombine light is emittedc😊

@davidd2661 3 ай бұрын

Fun fact: Photons are coming out of you, too, since you're warmer than 0K. Hopefully

@michaeltreu4152 2 ай бұрын

That is scary to you? lol. why?

@Xsiondu 2 ай бұрын

@@michaeltreu4152 because at the time I saw it and commented I felt like it was something that doesn't happen. Light doesn't "magically" escape from a flat metal surface. In the following days I understood how people could decide that some technology is witchcraft. But I have since remembered that part of physics where particles can transition from one excited state to a relaxed state and throw a photon off.

@arthurwilliams3479 2 ай бұрын

I think Photons are elecromagnetic waves, ie. RF, not particles, but what do I know, they just travel through glass lenses, and the medium called our atmosphere. Lasers are tuned RF emitters, but again I know nothing. ;)

@uwezimmermann5427 3 ай бұрын

I'll be teaching this in a few weeks again in a course on optoelectronics. I generally don't like "shorts", but this one was really click-bait for me - in a positive sense. First, the crystal is of course not a silicon crystal, but a III-V semiconductor. The photodiode gets hit by a fraction of the laser beam which is emitted to the rear through a nominally fully reflective mirror surface, but enough light is still escaping there to give a feedback signal to be able to run the laser diode at a constant emission, because even running it at a constant current will not keep the emission sufficiently constant. The material in the III-V crystal itself is grown as a stack with different doping and bandgap, restricting the light-producing emission to a small layer. The grooves on the top further modulate the vertical shape of the current density, making most of the current go vertically in a narrow strip through the recombination layer. Only this gives locally a high enough carrier density to allow for the laser process to happen, and it is now restricted into a strip through the whole crystal. The ends of the crystal are more or less atomically flat, the backside optionally also covered with a reflective layer, so that the light can bounce back and forth inside the crystal and the majority will escape to the front only.

@redmist4963 3 ай бұрын

This channel is only about semiconductor teardown and not one dedicated to university level lecture. Also the 60 second limit doesn't help in this case. But thank you for your insight nevertheless. It just rubbed me wrong when you called it click baity when in reality this channel is a rare gem in this site and is doing something cool and unique. There are other channels which do the explaining in detail with all the physics behind it .

@uwezimmermann5427 2 ай бұрын

@@redmist4963 I did not mean it in a negative way! I generally ignore all shorts since I don't appreciate the compression to one minute. But here I was attracted by the title and contents - and I really appreciate the close-up views. I then only wanted to complement the narration with the answers to some open questions. By the way : I have been a subscriber for quite a while...

@harryniedecken5321 3 ай бұрын

If the wavelength is in the 1300nm range, it might be a GaAs or InP based edge emitting laser.

@thehobbyist2431 3 ай бұрын

The flow of the electrons is very important for laser diodes, therefore they can have quiet complicated epitaxial structures which often are also etched to form a waveguide for the transversal direction of the emitting light wave. Therefore the emitting area is typically some microns below the upper surface.

@moritz584 3 ай бұрын

uhuh

@deang5622 3 ай бұрын

The flow of electrons is important for every electronic component. So is the flow of holes in semiconductor devices.

@jake_bytheocean 3 ай бұрын

your mom's the flow of holes

@spkumar2004 3 ай бұрын

I have been working in the communication industry for many years, I was wondering how the optical transceivers are made and the incredible engineering behind.

@ferrumignis 3 ай бұрын

You should see how complex solid state tuneable lasers are! Multiple sections that are either tuned by current injection or by tiny heaters on the active areas, and they all have to be controlled precisely to keep the laser operating on a specific longitudinal mode.

@octafed 3 ай бұрын

I've used my phone for that, and ended up burning permanent spots in the camera sensor. Don't use our primary phone for laser checking :D

@n0username0n 3 ай бұрын

Awesome news! I lost a phone to some acid whilst recording a timelapse dissolving some gold. Good to know it happens to others ahaha

@PsRohrbaugh 3 ай бұрын

Better your phone than your eyes

@charmio 3 ай бұрын

😂 Same! Though what's scary is I have no idea how or when it happened with mine. I was using my laser engraver and only noticed the next day there's a line burnt all the way across the phone, passing straight through the camera. Actually takes very interesting photos now. I didn't have my phone anywhere near it so must've been a reflection at some point. Always wear your glasses!

@onradioactivewaves 2 ай бұрын

* Please do not look at laser with reading eye* 😉

@geneard639 2 ай бұрын

Thanks for mentioning Laser Eye Safety. A lot of folks think these things are safe to play with. They are NOT.

@ElTurbandito 2 ай бұрын

unless the optical power output is

@TheAechBomb 2 ай бұрын

@@ElTurbanditoalways assume the knife is sharp; act as if every laser is over the safety limits, even when you know it's not, your eyes will thank you if you made a mistake or something was mislabeled

@ElTurbandito 2 ай бұрын

@@TheAechBomb want to hear something scary? Where I work we regularly fire a (well past) class 4 IR laser at chest height through the office and I can't get anyone else to wear laser safety glasses. The end target is covered with retro reflectors (that I put tape over) and the backstop is the accountant's office. help. My cries for safety go unheeded. (actually I'll have the chance to re-implement in a couple of months, we will make it more safe but gee the current setup is terrifying)

@TheAechBomb 2 ай бұрын

@@ElTurbandito this feels like it goes so far past satire to the point of absurdism, but it's pretty funny. I was just pointing out that safety precautions should always overestimate danger, because underestimating danger once can cause serious injury (in the case of lasers, your eyesight.)

@ElTurbandito 2 ай бұрын

@@TheAechBomb I get you, and in general I agree. I wish I could tell you this is satire! This is comic is posted on the wall: nerocam.com/DrFun/Dave/Dr-Fun/df9706/df970626.jpg That's just scratching the top layer of absurdity, I plan on making a more detailed post about this once the place closes. First engineering job out of school, cant rock the boat too much.

@michab5626 3 ай бұрын

To not damage your phone camera or your eyes it's best to check the datasheets of those components and the laser safety guidelines. Always make sure you're safe before starting any experiment of any kind.

@narrowgoat-scout 3 ай бұрын

This channel is brilliant. Showing me everything I could never quite see when I was my younger destructive/interested self. I upset many family members as a kid, dismantling their electronic belongings. Nothing was safe. I was too young to know its value 😂. I learned a lot ...

@blazeROTC 3 ай бұрын

My parents started going to thrift stores to buy me electronics to take a part. I had an obsession with dismantling electronics. But I could never get them back together

@narrowgoat-scout 2 ай бұрын

@@blazeROTC 😅 absolutely... gives you confidence in real life even if its false confidence

@cringemaki 3 ай бұрын

Oh man, my "childhood me" would LOVE to know this! My inner child LOVE this. Lmao

@NineteenOhOne 3 ай бұрын

Hey that's pretty cool! I'm surprised I haven't seen any content about this before, but glad I got it from your channel!

@sushillad1051 3 ай бұрын

Super knowledgeable information out of mind

@repairdroid77 2 ай бұрын

I've seen a laser emitting light under the microscope. One time at least.

@N3m3sls 2 ай бұрын

This is insane! Thank you for this incredible video footage!

@LotecAvenue Ай бұрын

Would be cool to see you do the same on a VCSEL (vertical cavity surface emitting laser). Some project many lasers at once. Some larger laser copiers use that, with different types of lenses etc.

@wilurbean 3 ай бұрын

1.3um (1300nm) is near IR and 1500nm down to 800nm is near IR.

@odissey2 2 ай бұрын

Usially Short Wavelength Infra Red (SWIR)

@JCR43221 2 ай бұрын

Shorts like this one is why i follow amd love your content.. thank you! ❤❤❤

@Mustafa_Dinc_ 2 ай бұрын

Liked, subscribed and the video was saved to my computer, Could you please prepare more comprehensive content about laser diodes and laser receiver diodes? Teşekkürler

@robinbrowne5419 27 күн бұрын

Cool 👍 It does seem weird that the laser just seems to come out of nowhere.

@tyronekim3506 3 ай бұрын

Nice video. I'm curious to know if your phone's camera sensor has any damage from recording the laser diode.

@michaeldeangelo4374 3 ай бұрын

Well explained

@FleshWizard69420 2 ай бұрын

I'd make every surface inside the laser casing a mirror for more laser, per laser

@NickNam3 3 ай бұрын

Very cool!

@Orc-icide 2 ай бұрын

Would love to see a 10W diode!

@BCDTech Ай бұрын

This is not silicon.

@TURBOSLAYERPWNZ 2 ай бұрын

I looked into a red laser pointer when I was a kid, it had very dead batteries and low power one anyway, to the point it was hard to tell if it was on or not. Dont repeat this since due to perfect focus on retina even weak lasers can do damage. Anyway if you look into laser it looks like there is a star, very small point, l bright and very very distant. Kinda same stuff as reflex sights.

@EvilmonkeyzDesignz 2 ай бұрын

@TURBOSLAYERPWNZ Every day, I resist the urge to look at a laser pointer ever since my Dad told me never to do it when I was a kid. I appreciate your description of this event, and your sacrifice.

@IanHilliard-cg4xy 2 ай бұрын

Pretty cool

@TheOpticalFreak 2 ай бұрын

That is so weird!!

@owenkegg5608 3 ай бұрын

I thought lasers typically required cavities? Are they simply for amplication and this is the source that illuminates the cavity? Or were my previous assumptions wrong?

@thehobbyist2431 3 ай бұрын

You are right. Lasers need three components: 1. Resonator (Cavity), 2. Active medium, 3. Pump source For an edge emitting laser diode like in this case, the resonator is just the front and back facette from the semiconductor. The reflectivity of the front facete where the laser light leaves the diode comes just from the refractive index difference of the semiconductor to the air and is about 30 %. The back facete is typically coated for a higher reflectivity of over 99 %. The photo diode collects only the light which is leaking from the back facete.

@user-ee8hi9kc8k 3 ай бұрын

Cool thanks

@gregorypirog6134 3 ай бұрын

The two flat faces of the Silicon P-N Junction are polished flat to form a mirror and parallel to form a tuned cavity. One mirror is 100% reflective. The laser light is exiting from the the mirror that is 99% reflective. Gregory/ The Pigeon Meister ... . 🐦‍⬛

@odissey2 2 ай бұрын

No, they are not polished. Just cleaved, which is simply scratched by the diamond blade and broken apart. Neither they are parallel - some lasers have to be discarded to pass QC

@LinkinPark4Ever1996 3 ай бұрын

I'm just as confused as before 😅

@user-zi5ty2dz4l 3 ай бұрын

heads up, I did something similar and the laser killed my phone camera lol

@AgentOffice 3 ай бұрын

Try without ir filter!

@duderguy1571 3 ай бұрын

I thought there was a tiny slot the lasing was coming out of for some reason 🤯 microscope it!

@robertparkinson2102 3 ай бұрын

You can have a slot where the laser light comes out. Search YT for DIY nitrogen laser. It operates in the UV. Please do not think about tinkering without protecting your eyes AND those around you. A friend had a note on his lab door, "Do not enter when warning light is on as my laser will be the last thing you will see."

@aclearlight 3 ай бұрын

Great work! I love your stuff...it both demystifies and celebrates the long chain of genius and hard work leading to today. Also makes me wonder just how much gold ends up being lost in the form of "E-waste".