I recently picked up this chinese-made
laser tattoo removal device from ebay now according to the specs this thing
should contain a really scary pulsed laser system inside and if so I'd love
to screw around with it when it comes to wacky eBay gadgets like this you never
know what you're gonna get. for one sellers often blatantly lie about the
ratings, and two this entire system cost less than having a doctor burn off a tattoo,
so it's not like you're can expect some state of the art medical system. now
that being said, I'm not super concerned with how safe or effective this thing is
because honestly I just wanna blow some stuff up with a pulse laser. in fact, if
this thing can produce pulses of say , I don't know like a million watts I'll be
pretty impressed, and if not I'll have to give it some much-needed upgrades. so yeah
without further ado let's fire this thing up. so uh, spoiler alert. this thing
packs some serious firepower. see all those little marks in the screen? this
thing is so powerful that blew a bunch of holes in my camera's sensor
without even taking a direct hit. what I'm getting at is that this thing
definitely isn't a toy and as tempting as it may be I do not recommend buying
one of these things. dangerous is an understatement for this laser and if you
don't have some high-end laser goggles you'll go blind using this thing. so yeah
please don't try anything you see in this video at home alright so here's
what all came with his unit. you got the laser head here and the main power supply
I got these treatment specific tips that actually might be able to change the
lasers output color. you got this really mysterious ointment, this funnel for
adding cooling water, a foot switch and then these these really sketchy laser
goggles. this manual here, if you could even call it that, turned out to be
completely useless for assembling this thing, but luckily putting this thing
together was really straightforward, like honestly a ten-year-old could assemble
this thing, and I'm not totally sure that's a good thing.
I went ahead and used deionized water for the cooling fluid as it turns out that
ultra pure water is actually a really really good electrical insulator. pretty
cool right? now before I power up the laser
I need something to protect my eyeballs because from what I hear, permanent
blindness is a bummer. now the hilarious thing is that the goggles
that came with this unit are the complete opposite color of my own
goggles that are rated for a YAG laser like this. I don't know about you guys
but I feel like this could be a huge issue so I'm gonna play it safe by
wearing these things. now unfortunately I don't have any visible tattoos that I
can burn off for this video luckily this is an all-in-one device. it
can also remove eyebrows, remove birthmarks, freckle, and then uh whatever
black doll is. my eyebrows probably could use a little bit of taming, but you know
what before I start pointing this thing at my face, I better test on something
like this piece of metal over here. all right I got the energy maxed out here we
go oh my gosh that is loud it's literally blowing craters in the
metal .that is a lot of damage check out those insane plasma fireballs the surface must be getting incredibly
hot. I was not expecting this thing to be so strong especially out of the box like that's just blowing craters in the metal
with nothing but light like that's insane! this thing packs some serious power.
right here I have a two and a half kilo chunk of tungsten. let's see what happens
when I hit it with the laser. in case you don't find these little craters
impressive tungsten has a melting point of over
three thousand four hundred degrees Celsius the highest melting point of all
pure metals. now I wouldn't 't even be surprised if the center of the fireball
is hotter than the surface of the Sun. I know what you're thinking, what happens
if you get hit by the beam? well one way to find out I guess
oh wow it kind of tickles well I mean yeah it hurts but not nearly as bad as I
was expecting that's actually pretty neat. now the
reason it's not leaving craters in my skin is the fact that my skin just
doesn't absorb this light very well. now this is especially useful for removing
dark tattoos, as the laser selectively destroys the dark ink while leaving the
skin untouched. well sort of. as an example of this, let's pretend I've made
the biggest mistake of my entire life and the only way for my family to love
me again is to get it burned off. well lucky for me, this is just another day at
the office for this laser well that sucked I mean yeah it
erased the ink and actually did a really good job but maybe maxing out the power
wasn't the best idea here ah whatever my skin will probably heal.
now unfortunately burning off a tattoo isn't always so simple. for one my pale
skin and dark ink make selectively destroying the ink a lot easier. but the
thing is lasers are racist! I mean those with a darker complexion are a lot
more likely to receive burns because their skin absorbs more of the
light. and this isn't even the only complicating factor, I mean tattoos
come in a huge variety of different colors you can't use just one laser for
all of them. as an extreme example of this I've tattooed these two boards here.
now when I try to remove the one on the darker board it's hard to prevent
destroying the surface along with the ink. but even on the lighter board I run
into issues. now the dark ink comes off pretty easily but the red ink is
essentially untouched so now what do we do? that's where this witchcraft comes in.
so inside this tip is a crystal of potassium titanyl phosphate, or KTP for
short. it splices two IR photons together to make one green photon via a process
called second harmonic generation. now the fact that you can just screw this on
to the tip to make it green is literally insane because it's usually a lot harder to pull off nonlinear optical processes like this the green light does a much better
job at removing the red ink, but really this isn't much of a surprise since red
and green are on opposite sides of the color wheel. okay so it works on wood but
how about skin? uh one way to find out oh oh holy heck that hurt! it turns out a
lot of things absorb the green light better, and then includes my skin! so
sorry guys but I'm gonna have to pass on lasering this one off. I guess it's
permanent now. oh yeah rubbing alcohol is a thing isn't it?
so what else can I do with the green beam? well how about cleaning some dirty
coins oh wow look at that good as new!
the polka dots give it an added touch don't you hate it when you transformers get
all rusty? luckily with this laser you can burn the
rust right off. oh wow that's amazing I didn't even need to use corrosive
chemicals just an unimaginably dangerous laser. aluminum foil reflects all but
just a few percent of the light that hits it, so is it possible that we can
shoot through it anyway? I guess so! well that's actually pretty crazy because
remember that's just light that's shooting through the foil. if we look at
it in slow motion, you can see little pieces of burning aluminum flying off
of the metal so that's actually pretty neat. oh yeah see all those little spots
in the picture? this is when I noticed them too. ah heck. turns out that even without
a direct hit, the laser still managed to blast a bunch of holes in the camera
sensor and since there's no fixing that, I might as well keep lasering stuff until
the entire sensor goes blind. this one was suggested to me by youtube user Vidduley and it's just a block of clear acrylic. now even though it's nearly
transparent it can still burn its entire beam path into the plastic.
now it's funny because I tried using this effect to engrave stuff in the
acrylic but I just ended up vaporizing the surface of my table behind the block. a
balloon seems like a silly test compared to everything else but check this out well that was surprisingly difficult
what gives? it turns out that the hot plasma formed on the surface ends up
absorbing most of the laser pulse energy this actually protects the material
behind it somewhat. this is why military laser weapons are almost never pulsed.
when it comes to burning stuff with a powerful laser it's hard to find
something easier to set fire to than a match. but this is a pulse laser so it
doesn't behave like you'd expect in fact the laser obliterates match
heads without even igniting them. I think the explosions at the surface must be too
violent to allow a stable flame to form hmmm I wonder if this laser can burn a
CD? oh yeah punches straight through it even if I flip it to the shiny side it
still vaporizes the metal coating. that's pretty crazy
oh yeah I can't forget about these goggles that were sent with the kit.
surely the sellers care about our safety right? huh look at that. yeah
that's right, your retinas would look like a slice of Swiss cheese if you trusted
these things. big oof for those who bought one of these kits and used the
included goggles. look what happens if I don't point it at anything.
oh yeah the air ignites! think about just how crazy that is.
air, which is basically transparent, is exploding in the laser beam. if you want to
light the air on fire with nothing but light, you need some gigantic power
densities. in fact the threshold is something like 300 billion watts per
square centimeter. now that gives us a lower bound on power density but what's that
say about actual output power? the seller claims that this laser outputs a max of
2 joules in each 10 nanosecond pulse. now 2 joules may not seem like a lot of
energy, but when it's dumped in just 10 nanoseconds, you're talking peak powers
of 200 million watts! but let's just pretend like the seller is a total liar.
how do we measure the output power ourselves? well it's not as easy as just
pointing it at a meter, as it turns out that most sensors just don't like eating
mega watt class laser pulses very well that being said we can get a pretty good
estimation using just a tiny bit of math calculating actual power from the power
density means that we need to find the minimum size that the laser can focus
down to. now this is difficult for me to measure directly, but we can use the fact
that lasers tend to take on a Gaussian beam profile in order to make some
estimations. in the simplest case you have a wave traveling along Z and
polarized along X that takes on the fundamental transverse mode of the laser
resonator. now when this happens the time-independent electromagnetic field
looks approximately like this. now if you're thinking oh wow I'd rather stab
my eyeballs out than try working with that, well you're not alone, but actually
it turns out that the special mathematical properties of the Gaussian function
mean that these beams can be described with just a few simple parameters and
then manipulated with simple algebra I started by measuring the beam divergence and then calculated the waist radius using the laser's wavelength' and this
gives a diameter of approximately 10 microns.
now equating a beam of this size to the minimum irradiance required to ionize air
gives a minimum laser output power of a hundred and fifty thousand watts. but the
thing is, there's no way that this thing is operating even close to the perfect
Gaussian beam, so if it's say ten times worse with a hundred micron beam
diameter, well that gives an output power of fifteen million watts. and now this
seems crazy, and it's actually several times higher than the instantaneous
electrical power draw of the entire town that I live in, but it is actually
reasonable. all right so I have a pulse laser with output the megawatts. now
blowing stuff up is always gonna be fun but what else can I do with it?
well how about using it to build a laser pumped laser? there's a lot of ways to
pull off laser inception by using one laser to drive another, but today I'm
feeling old school and I also want to play with some chemicals. Here I have an
assortment of organic dyes, some that i synthesized years ago and others that i
bought online. now under the right conditions, these dyes can be used as a
laser medium that can output a huge variety of colors. oh wow this brings me
back to my time in academia! well this does at least. I'm not exactly throwing a
party though, I just need to make some solutions of these dyes in ethanol.
these dyes are extremely photoactive so a little goes a long way here. in fact I
only need something like 50 milligrams per 100 milliliters of solvent and even this may be too much so I'll probably end up diluting them. now a precise
concentration isn't super important but too much dye in the solution will kill
the output. I started by filling a cuvette with rhodamine B dye solution
diluted to about 10 percent of the original now placing the cuvette
directly in the beam path does give some colorful light but I can't be sure that this
is actual laser emission. by kicking the cuvette off at an angle the green laser
beam is refracted through the cuvette so that it doesn't line up directly with the
potential dye laser beam. now sure enough this reveals that the liquid is actually
operating as its own laser as there is now an orange beam exiting at an angle to
the original pump green beam. now that is pretty cool. since there's still so much
green light left exiting the cuvette i upped the concentration to utilize more of
the pump light and this actually dramatically increases the output. I
found the best results using about a half a millimolar of rhodamine B. now
notice that I'm not using any sort of external mirrors to act as an optical
resonator. in fact the roughly 10% reflectivity of the cuvette walls
provides enough feedback to achieve a massive amount of optical amplification.
now that's a material that likes to lase! since the reflectivity is the same
on all sides of the cuvette you get laser emission from each side of the cell,
with one face typically favored stronger than the others. now of interesting
notice is the presence of the side beams running 45 degrees to the main beams. now it turns out that the corners of this square cell act as strong enough
retroreflectors to form laser cavities here too, thus forming this beautiful but
terrifying laser star of insta blindness sticking a mirror on one end causes the
majority of the dye laser output to exit in the opposite direction, giving some
sort of controllability. still though I wasn't comfortable viewing the output in
person as the peak power is still very high and my goggles don't even block this
color. this is a real bummer too because orange lasers are very hard to
come by. in terms of peak output power this laser tattoo removal system is
actually the most powerful laser that I've shown on this channel, so what
exactly is inside this beast? I tore down the main unit to see what's inside and it's
actually pretty simple. so you have some control circuitry over there you got a
water pump and water cooling reservoir a switching high voltage power
supply then an energy storage capacitor right here which supplies energy to the
pulse laser. now notice there aren't any optics in here. in fact the entire laser
cavity is contained within the handle tearing this down reveals that the laser
inside is old-school it's actually quite similar to the first
laser ever built. there's a flash lamp here that pumps light into a crystal of
neodymium doped yttrium aluminum garnet or Nd:YAG for short. this energizes the
neodymium ions in the crystal and sitting between these two mirrors here
allows it to operate as a laser. as a sidenote Nd:YAG was one of the
first laser media ever discovered and it's still widely used today so it's
actually pretty cool that it survived the test of time like this. there's a special
optic that's inside of the cavity here which allows it to produce such absurd
pulse powers. now initially it absorbs the light coming from the crystal which
actually kills the laser output, but what this does is it allows the crystal to
build up a bunch of energy while the flash lamp fires. but after the optic
absorbs enough light it suddenly becomes transparent, effectively exposing the
highly energized crystal to the cavity mirrors. now this causes all that energy
to get dumped in an incredibly short amount of time, limited by the time it
takes for the light to make a few bounces through the cavity. now this
process is called q-switching and doing it passively with this little
optic is probably the simplest method in use. when this q-switched laser fires,
pulses have a duration of about 10 billionths
of a second which means that light only travels about three meters during this
time. to put that in perspective, pointing a laser pointer in the sky for one
second will produce a pulse that is 300,000 kilometers long. it's really hard
to fathom timescales this tiny but amazingly there are already lasers that
run over 10 million times faster than this so now that I've gone through the
trouble of tearing it apart is there anything I can do to make it stronger?
well removing the q-switch would actually increase the energy a bit but
that's at the cost of a dramatically decreased peak power. in fact if I want
to increase the output my best bet is to feed more energy to the lamp. looking at
the energy storage capacitor I see that it's rated for 1,400 volts at 100
microfarads. when I actually measure the live voltage through a voltage divider I
see that it only gets charged to a max of about 800 volts, or only about 1/3 of
the energy that it's rated for. as a side note using this measurement as a way to
estimate peak power actually gives a similar result to the one I got earlier
but this time I get about 30 million watts. for funsies
I used this number to calculate the strength of the electromagnetic field at
the beam waist and as expected it's insane. look at that, an electric field of
over billion volts per meter, that's hundreds of times stronger than what the
accelerators produce in the Large Hadron Collider. now granted that's over
a tiny distance but it still shows the potential of lasers in desktop particle
accelerators. all right so back to modding this thing. so I guess I have
two main options here to increase the output. I could crank up the voltage
feeding the capacitor, but since the impedance of the flash lamp is nonlinear,
a higher voltage would mean a shorter pulse length and that would
disproportionately overpower the flash lamp. my guess is that charging the cap
up to its full rating would annihilate the lamp in one shot. so I guess my other
option is to add more capacitors this will definitely increase the energy but will
be done more gently over a longer pulse I went ahead and added enough capacitors
to triple the energy in the circuit so without further ado let's test this
thing out. all right here we go that was bad. did it just break?
it broke! it turns out that some underpaid grad students in the 60s came
up with these empirical equations that describe the lifetime of a flash lamp
with its drive energy. in fact there's a dramatic relationship here, to the power
of eight and a half actually! that means that tripling the drive energy for given
pulse length will actually destroy the lamp about 11,000 times faster than running
it at its original energy, so it's no wonder that the lamp exploded. as a sidenote
pretty much all the laser science in this video can be found in this book
from 1976 I learned a bunch from it when I first
read it four years ago and the info is still just as relevant today. now for
those out there who are interested in experimenting with old-school
flashlamp pumped lasers you'd be hard-pressed to find a better resource
than this. well I hate to have such an anti climactic ending but I think I've
destroyed enough of my equipment for one video. but seriously I obliterated the
Sony camera that I just bought last year and I even put a few more holes in this
camera that I'm shooting with right now now including the tattoo laser that I
destroyed this was by far my most expensive video yet. now luckily I have
some dedicated patreon supporters that kept supporting me even when I can't
upload very frequently so as a thank you to you guys, imma let you guys see this
video first before I make it public anywhere else. so yeah a big thank you to
you guys. one last thing. so even when I'm not uploading to my channel I'm usually
posting content to my other social media so be sure to check those pages out via
the links in the description I especially recommend watching the most
recent video my backup channel of an amazing lightning storm I experienced
while tornado chasing plus to all the makers and home
experimenters out there I highly recommend checking out my discord server
as there's a ton of knowledgeable members there and they're always working
on awesome projects. so yeah until the next time stay safe and happy lasing!!!
ayyyy this is my video :D
He reminds me of Scout from Team Fortress.
Very interesting but those calculations made me feel pretty fucking stupid.
This guy sounds like Kevin McAllister at the grocery store talking to the lady clerk
Laser hair removal costs thousands of dollars. Scar treatment too, I had a laser scar treatment that was about 1000 dollars for a single session.
Should’ve just bought my own laser.
Very interesting, and enjoyed the dry humor.
He sorta laughs when a breathy heave on every sentence and it's bothering me.
HE IS NOT JOKING ABOUT THIS THING NOT BEING A TOY YOU WILL GO BLIND DONT BE STUPID.
I want one. I don't need a tattoo removed, I just want a 1,000,000 watt laser.