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what are nm?

Ash

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damn, that is small!
Here are some pics to help illustrate;

1. Nanometer size comparison pictures.


These pictures show about how large a nanometer (or 100nm - 100,000,000nm) is in comparison to regular everyday stuff:
So a 405nm laser (at it's focal point) is exactly 405 nanometers across. A 660nm laser (at it's focal point) is exactly 660 nanometers across.
A collimated laser (beam) can be <1mm to +10mm
2. (Attached) The visible spectrum diagram indicates where different types of waves (including light waves) travel on the wavelength spectrum.
You can see that in the center is the "visible light", and hopefully you notice that a 405nm laser (close to 400) would be purple and a 660nm laser (close to 700) would be red.
To answer an earlier question of yours;
There are many different colors of lasers out there other than "red", "blue" and 'Green", so they have to say which Red: 635, 650, 660, 670, etc...
Here's a pic with all the lasers in their respective colors that are available:
(also attached [2.])

-Now another term people keep throwing around in this thread is DPSS Laser. This is an acronym for Diode Pulsed Solid State Laser. This is different than a regular Diode Laser (Bluray, Red, IR).
DPSS can be illustrated here:


As you can see from the diagram for a green DPSS, the (barely visible) light emitted from a powerful 808nm (Infrared) Diode passes through a Nd:YVO4 crystal which turns it into 1064nm (even more invisible) light. That 1064nm light is passed through a KTP (Potassium Titanyl Phosphate) crystal which doubles the frequency of the light (thereby splitting the wavelength by 1/2) 1064 x 1/2 = 532.
Different crystals and different pump diodes are used in combination to make every color out there, but most DPSS lasers are very expensive (other than green).

And one more image just to make this post very heavy:
 

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1Nick

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damn! thats descriptive. smaller than i thought :O
 

Crazy Jay

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For how I used to think the sizes of molecules were... based on the pics... they seem a bit larger to me now
 

Traveller

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damn! thats descriptive. smaller than i thought :O
So the next time you're getting an X-Ray... think about the fact that "waves" passing through your body are about 1nm apart... :D

Btw, Ash is clearly in the know and if you want to [try to] catch up, start over at Sam's Laser FAQ.


p.s. So like my guess is you didn't make your avatar, huh... ;)
 

chipdouglas

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i agree with tj on this.... just his rep alone should prove that. I don't know if i have ever read false information he has given.

michael
 

Traveller

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i agree with tj on this ... I don't know if i have ever read false information he has given.
Agree with what, that he was first? Sure he was first. I didn't see anyone post to the contrary and I also didn't see anyone suggesting he had given any false info, now or in the past... :undecided:

So, what's your point, exactly... ?
 

pullbangdead

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So a 405nm laser (at it's focal point) is exactly 405 nanometers across. A 660nm laser (at it's focal point) is exactly 660 nanometers across.
A collimated laser (beam) can be <1mm to +10mm
Nice pictures and all, but this sentence falls somewhere between misleading (at best) and just plain incorrect (at worst).
 

pullbangdead

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Please explain exactly how it is incorrect.
kthxbye :whistle:
k

So a 405nm laser (at it's focal point) is exactly 405 nanometers across. A 660nm laser (at it's focal point) is exactly 660 nanometers across.
A collimated laser (beam) can be <1mm to +10mm

First, wavelength is completely, 100% independent of beam size, so saying "at it's(sic) focal point" is misleading. Beam size can depend on wavelength, but wavelength does not in any way depend on beam size. The wavelength of a 405nm laser is 405nm at the focal point. It's also still 405nm 300 miles away from the focal point, so adding "at it's(sic) focal point" is just misleading.

Then you say "a 405nm laser is exactly 405 nanometers across." What is this "across"? 405nm is the wavelength, which is measured in the direction the light is traveling. There is no "across", as if you're measuring the size of the beam waist. The size of the beam waist can be somewhat dependent on wavelength, but in any practical case on this forum, optical elements are more important in determining beam waist, whether you're at the focal point or 300 miles from the focal point. So saying the laser is 405nm across at the focal point is at best misleading, because the beam waist is dependent on way more things that wavelength, and at at worst incorrect because it seems you're saying that measuring the beam diameter gives you a direct measurement of wavelength, which is absolutely untrue.

And reading further, I had included your collimated beam size comparison, as on my first reading it seemed to indicate a small range of beam diameter possibilities. On my second reading, I see now you are completely correct, because what you wrote includes every single size possible: <1mm, >10, and every single value in between (inclusive of 1 and 10). Your beam could be a micrometer across, or it could be a mile wide, and indeed, your sentence does allow for both these possibilities, as well as any other positive value of beam size, so it is technically 100% correct. The real limits on size only come on the small end, and there are host of factors that come into determining minimum beam size, including (but not limited to) wavelength.

thxbye
 
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chipdouglas

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you posted "Such is your fate, known as LPF's friendly troll first, Lazor Science Buster a resounding second..."

you insinuated that just because he is a troll, his info is less valid. so i agree with tj that he is indeed a valuable and knowledgable member.


michael
 

Ash

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First, wavelength is completely, 100% independent of beam size, so saying "at it's(sic) focal point" is misleading. The wavelength of a 405nm laser is 405nm at the focal point. It's also still 405nm 300 miles away from the focal point, so adding that is just misleading.
I wasn't saying the wavelength (color) changes away from the focal point at all. I am using the "focal point" example to illustrate size (in nanometers) of the beam diameter. Please don't get nm (size) confused with nm (color) even though they are the exact same thing. The reason a 405nm laser is violet (405nm-color) is because the light waves are oscillating at a maximum distance of 405 nanometers (from crest to trough).
The size of the beam waist can be somewhat dependent on wavelength, whether you're at the focal point or 300 miles from the focal point. So saying the last is 405nm across at the focal point is at best misleading, because the beam waist is dependent on way more things that wavelength, and at at worst incorrect because it seems you're saying that measuring the beam diameter gives you a direct measurement of wavelength, which is absolutely untrue.
I am not asking anyone to measure the beam-waist at the focal point (despite it being done all the time in labs). But with all other variables aside, the diameter of a 405nm laser (at it's focal point) is narrower than the diameter of a 660nm laser (at it's focal point) by 255nanometers (length) simply due to the properties of coherent light waves that oscillate at specific wavelengths. You can't argue with science.
-I hope you understand my point. :eek:
 
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pullbangdead

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Beam size doesn't equal wavelength, you're mixing terms and ideas. I can't even really tell what it is you're trying to convey, so no, I don't think I understand your point.

And wavelength is measured crest-to-crest or trough-to-trough, not crest-to-trough.
 

Ash

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Beam size doesn't equal wavelength, you're mixing terms and ideas. I can't even really tell what it is you're trying to convey, so no, I don't think I understand your point.

And wavelength is measured crest-to-crest or trough-to-trough, not crest-to-trough.
Thanks, yeah crest-to-crest, sorry, was thinking wave amplitude. :p

"Beam size doesn't equal wavelength"? But wavelength determines beam-size (diameter at the focal point).
Seems we are going in circles here. :thinking:

My point in simple terms: You can focus a bluray laser to a smaller point than you can a red laser.
-End
 




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