Hi! In this video we’ll
take a closer look
on green laser pointers.
They have become so cheap
that lots of people now own
them but may not be aware
of a major safety issue with the cheap ones.
To save costs, an important component
to filter out invisible, infrared laser radiation
may be missing in your laser.
I will test my green lasers for this
and even test if the mighty
Hercules has this issue.
Powerful lasers will damage your eyes.
Always use laser safety glasses.
Especially when using reflective
glass in front of them
and invisible lasers as I do in this video.
Now, I’m used to handling powerful
lasers with a visible beam.
They can be scary enough
but powerful, invisible laser
beams give me shivers.
Therefore, I have bought
some pro-level safety glasses
that will protect my eyes against
both green and infrared beams.
I cringed at the price of these
but my eyes – my vision –
is worth a lot more to me.
It may be a surprise to most
that green lasers can emit
infrared radiation too.
Why would they do this?
Aren’t lasers supposed to be monochromatic?
Tightly centered around one wavelength?
532 nm in the case of
the common green lasers.
Actually, all the radiation from
such a laser starts as infrared.
Inside it is a powerful, infrared 808 nm laser
that is converted to 1064 nm infrared
which is then converted to
the visible 532 nm green.
The crystals aren’t 100% efficient
at converting the infrared.
A textbook design therefore has
a filter that blocks the remaining infrared
but lets the visible laser light through.
This DPSS-design is relatively
complicated and expensive.
So to make cheap laser pointers
it is tempting to simply
leave out the infrared filter
or only include a dirt cheap, inefficient one.
I want to see what they
did with my green lasers.
But how can I tell if the lasers
emit invisible, infrared radiation?
Many – if not most – digital cameras
will detect near infrared light.
Here, I test my camera with
some ordinary remote controls.
My eyes can not see this
low-level infrared radiation.
But the camera can.
Oddly enough it is recorded as a violet color
even tough it is a deep, deep red color.
But I don’t trust my camera
for all infrared wavelengths
and want a more direct way
to see an infrared beam
without shining it directly into my camera.
The green laser beam is also very bright
so I need to filter that out
before making a clear
detection of infrared light.
The solution is optical filters.
I found some affordable ones on eBay.
One lets infrared light pass through
but blocks visible light.
And another one lets visible light pass
but blocks infrared light.
To make infrared visible, I’ve also
bought some different IR-cards.
Two of them are affordable
and the third has a huge
detection area and price tag.
They will all detect the IR from a remote control.
One of them is even meant for it.
The green one is for much
more intense radiation
than from a remote control
but will emit a noticeable
green light in a dark room.
More visible to my eyes than to the camera.
Since I always question
unbranded stuff bought online
and want a control test to see
how infrared radiation behaves in my setup
I bought some infrared lasers too.
One emitting 808 nm like
the pump diode in a green laser.
And one emitting 980 nm.
Unfortunately, I couldn’t
find a cheap 1064 nm laser
to represent the other infrared
wavelength in a green laser pointer.
But my setup should work
for that wavelength too.
Let’s try the 980 nm laser first.
It is not visible to the camera or my eyes
until it hits one of the detection
areas on any of the cards.
There I can clearly see it as either
an orange or green dot on the cards.
The 808 nm laser is a little different.
It is detected by the camera and only
works well with the two orange cards.
The green one has little to no
reaction with this wavelength
since it is outside the
card’s detection range.
The green card however has an advantage.
It doesn’t need to be
recharged with white light.
The two orange ones need a recharge
once in a while to have maximum response.
Now, we can test if the
optical filters work as advertised.
The black one should let infrared pass,
while the clear one should block infrared.
Yep! The black one does let infrared pass
and clearly blocks visible light
since it looks opaque to our eyes.
Let’s put the clear filter in between
and see if it really blocks infrared.
Ah yes! We have a setup
working as intended.
This is perfect for detecting any infrared
leaking from a green laser pointer.
I’ve got three cheap,
unbranded, green lasers to test.
Let’s start with the weakest one.
It is supposed to be less than 5 milliwatts
but it may be more as explained
in one of my earlier videos.
Oh dear… not a good start….
It is clearly emitting infrared
as detected on the card.
Let’s try a more powerful
one at 50 milliwatts.
This one is leaking infrared too.
Here’s a different laser for comparison.
A 505 nm cyan-green laser.
There’s no infrared coming from this one
since it is not a DPSS-laser.
No infrared laser diode inside it.
Just one emitting 505 nm directly.
It’s the same with blu-ray lasers.
They have a laser diode emitting
405 nm laser light directly.
No infrared from these too.
Same story with red laser pointers.
Nothing detected from
this orange-red at 638 nm.
The powerful 200 mW 660 nm
laser reacts a little differently.
The black filter can’t completely
block this wavelength at this power level.
But no infrared is coming from this laser.
No orange dot on the card
and it goes through the clear filter too.
All right, let’s try the last
of my cheap, green lasers.
It is also up to 50 milliwatts.
Look at this ridiculous label.
It says Class IIIa but that class
is only for lasers up to 5 mW.
Don’t trust this laser to
comply with any regulations
even though it says so
at the bottom line.
Not surprisingly, this
one emits infrared too…
It appears to be a very common
issue with the unbranded, green lasers.
I also own some branded,
green lasers from Laserglow.
They are very expensive so they
better have an infrared filter in them…
First up is the Aries.
This one has a 1200 mW
infrared pump diode
so I wouldn’t be surprised
if a little infrared comes through
even if it is filtered.
My IR-filter still lets up to 2% through.
Here we go. Time to see
if this a quality laser or not.
Now, this is how it is supposed to look like.
Little to no infrared light is coming through.
Only a massive amount of
green laser light as expected.
Let’s step it up a notch
to my most powerful green laser.
We are now dealing with
a 2500 mW infrared pump diode.
Surely, some of it must
make it through to the output?
No! I don’t see any infrared leakage.
The quality of the infrared
filter must be sky-high.
As the rest of the components.
This is a high-quality laser.
I love it.
The conclusion based on
my green lasers is clear:
Cheap, unbranded ones should be
assumed to always emit infrared radiation
while expensive, branded ones
can have proper filtering.
So it is a good idea to buy
a small infrared filter
and use it in front of the cheapos.
With some lasers you may even
be able to take the housing apart
and fit the filter inside it.
If you buy a smaller filter than I did…
Anyway – as always – be careful
when handling lasers.
Maybe they are emitting more
than you can see
and I want you to be able
to watch my future videos 🙂
Thanks for watching!
Subscribe if you want to see
more laser and science videos.
I have also finally launched
a Patreon account
so go check that out.
Link in the desciption.
Any support is appreciated.
Even a like makes me smile
so click like if you did like the video.
Bye for now!
Hi! In this video we’ll