Cheapo Diode on Ebay?

Bandanna · Feb 24, 2010

There is a 150mW 405nm on Ebay for about 20$ shipped. Is this a normal price? I feel like it is really inexpensive and may be flawed in some way. Isn't 405nm pretty low on the visible light spectrum? I sort of want a diode that will produce a decent beam closer to the 530nm range. How do prices on these guys run?

photonaholic · Feb 24, 2010

Bandanna said:
There is a 150mW 405nm on Ebay for about 20$ shipped. Is this a normal price? I feel like it is really inexpensive and may be flawed in some way. Isn't 405nm pretty low on the visible light spectrum? I sort of want a diode that will produce a decent beam closer to the 530nm range. How do prices on these guys run?

Welcome to the forum. Let me explain how green lasers work, you could never afford a green diode, they are not readily available.

Green lasers use an infrared diode to pump a crystal then the crystal turns the light green.

405nm is near ultraviolet, we call these blu ray diodes.

Read the many pages in this link, you will really like it!

Sam's Laser FAQ: Welcome Page

Bandanna · Feb 24, 2010

Ah, sorry. I actually had just read a thread that mentioned that green laser diodes didn't exist and they were DPSS, I think. I've read around the forums a bit, but still very much a novice. I do like electronics though, especially lasers. I'm interested in putting my own together as a project. How near is 405nm to ultraviolet light? I understand that the vividness of the beam is the result of a multitude of factors, mainly the air around it, but even still, if I had some sort of visualizer or very humid atmospheric conditions would my eyes physically be able to perceive 405nm wavelengths, or is just simply too dim? I think I've read somewhere that since the wavelengths are shorter in blu-ray and ultraviolet lasers that the beam might be more visible since the wavelengths refract differently off of particles in the air than that of low frequency wavelengths, but there was not much elaboration.

hugo999999 · Feb 24, 2010

Bandanna said:
I think I've read somewhere that since the wavelengths are shorter in blu-ray and ultraviolet lasers that the beam might be more visible since the wavelengths refract differently off of particles in the air than that of low frequency wavelengths, but there was not much elaboration.

hi
im wondering this too. exactly how bright is a 405nm compared to say a red 650nm laser? what power do you need to have to get a visible beam with smoke and without smoke?

thanks, hugo.

photonaholic · Feb 24, 2010

The sensitivity scale I posted says it all.

Blu ray is close to UV, so it appears dim to the human eye.

650 is close to IR so it appears dim to the human eye.

If you want stunning visual beams, go green.

It's right there, just look up.

Particles in the air, like fog or smoke will make any beam appear brighter, even green.

But no matter what you do, the photo receptors in your eyes follow the graph above.

Bandanna · Feb 24, 2010

The thing that seems to be confusing me is that on youtube there are many videos claiming that the people are in the videos are using 405nm lasers but they seem to have a very nice beam at night or in fog, etc..
Even though 405nm is very close to ultraviolet light it is still for the mot part visible, all though not as visible as a 530nm laser would be?

dysfunctional · Feb 27, 2010

thats because on camersa and camcorders the video pics up the uv rays for instence if you point a camera while its on at you tv remote and hit a button you can see the uv led sending a purple light out. but 405 sounds like a decent number if your going for visual effects. given your not trying to find the beam in the air

hugo999999 · Feb 28, 2010

if you want visual effects don't go for 405nm as it is very dull per mw compared to other wavelengths, even red. like dysfunctional said cameras pick up infrared light like that of a tv remote, and im pretty sure they do this for uv as well. a friend of mine has a ultraviolet laser and it appears a lot brighter on a camera, mainly because our eyes cannot focus on it the wavelength well or see it. its not so much that uv is shown brighter on a camera, its that all wavelengths are shown at the exact same brightness so uv is shown as bright as any other colour (to an extent).
hugo

Bandanna · Feb 28, 2010

Aw man, That's sort of a bummer to hear.
Stupid, imperceptive, rod and cone, human eyes...

So when is it that one can see a beam, I mean is it even possible to see a beam at all from a 405nm with nude eyes in a dark foggy room, or is even that for the cameras?

I have all these questions because I'm a poor deprived being who's never had the privilege of witnessing a 'real' laser.
So, sorry if this all seems nit-picky but I need to douse any ideal expectations I may have now before I go and try to put something together; you know?

hugo999999 · Feb 28, 2010

well im not quite sure, but i know 405nm is less visible than 650nm and i have a fairly powerful 650nm that is just visible without smoke or fog. i would say you would need at least 200mw+ of 405nm for it to be visible. as for fog or smoke though, i can see a 5mw red laser in slight mist, smoke is even better. (note this is all when its dark, at daytime you wont see anything).

photonaholic · Feb 28, 2010

just get a cheap greenie, you will be so glad you did.

My first green pointer was so damn impressive, I could hardly put it down, and it was like $20 shipped to my house.

Bandanna · Feb 28, 2010

That sounds like a good idea. That should tide me over until I can get some stuff to try and build my own. My whole goal is lasers + mirrors. I honestly don't think burning is all that great. It's like the cheap party trick aspect of lasers. I want to experiment with lasers, mirrors, and motors and produce some of those out of this world effects that I've been seeing around these forums.

genius5th · Mar 7, 2010

I like the chart and modules

mfo · Mar 7, 2010

dysfunctional said:
thats because on camersa and camcorders the video pics up the uv rays for instence if you point a camera while its on at you tv remote and hit a button you can see the uv led sending a purple light out. but 405 sounds like a decent number if your going for visual effects. given your not trying to find the beam in the air

hugo999999 said:
well im not quite sure, but i know 405nm is less visible than 650nm and i have a fairly powerful 650nm that is just visible without smoke or fog. i would say you would need at least 200mw+ of 405nm for it to be visible. as for fog or smoke though, i can see a 5mw red laser in slight mist, smoke is even better. (note this is all when its dark, at daytime you wont see anything).

I must have weird eyes then, because I can see my 85mW 405nm beam much clearer than I can my 225mW 650nm beam.

ossumguywill · Mar 7, 2010

^agreed. I think the refraction thing has some merit, because in my house while the dot of the 100mW 405nm is dimmer than the dot of the 200mW 650nm, the beam of the 405 is actually much clearer. Not like it reflects off dust more, but like it is reflecting off very small particles in the air. Maybe there are very small particles in the air that 650nm lasers can go around, while the smaller 405nm lasers reflect off of them?

Bandanna · Mar 7, 2010

Hmmmm... From what I read, A lot of people are able to see 405nm beams with less mW than reds. It makes me want a blue now.
I want to try to make my own, but I'm afraid to solder sensitive components..
I just burnt up a couple of toggle switches the other day... They no longer switch.:undecided:

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