Diodes questions....

[dweglarz13]

Ive tried searching the forum and found some threads about blue vs. green visibility, etc.etc. and many different opinions. So, I'll ask here.
I am trying to understand something as far as diodes go, and beam visibility.

Lets say you had 3 different diodes.
PL450 single mode at 150mw
m140 at 1.5W
9mm at 1.5 W

Which of these diodes would give a more visible beam?

Thats it.....no burning, power, etc....Just a simple question and why.
I understand the 450 is a different wavelength, but that shouldn't make that much of a difference right? Which of these diodes show a more pleasant beam to look at with the naked eye(and glasses of course)??? Thanks. Believe it or not its hard to find a solid answer to this question.

dave

 

[Zeebit]

The higher the power the more visible a beam will be.

Which of these diodes show a more pleasant beam to look at with the naked eye(and glasses of course)???

You wont be able to see the beam with safety glasses on.
Its a matter of personal preference. The PL450 is a single mode and you will get a nice thin beam while the M140 and the 9mm diodes are multimode and you will get a thick beam.

 

[NKO29]

The 9mm diode. Even though there is a difference of 5nm, it will be SLIGHTLY more visible. The pl450 is the least visible because of it's low power. 450nm is closer to the easiest wavelength (~530nm) for humans to see and that is why it will be more visible at equal powers.

 

[dweglarz13]

Okay, now let's say we are talking about the Pl450 that is 1.4W.
What you guys are saying is this will be a better visibility to the eye than a 1.5 W M140 or 9mm?

another question.....is the 1.4W PL also single mode like its weaker counterpart?
And, what determines a "straighter, more uniform beam," as opposed to some beams I see that seem to be thick in some spots than more focused in others? I understand you want a tight spot for burning....but as far as a beautiful beam goes, which diode would give more of a beam profile that is more uniform and tight throughout a longer distance. I know it sounds weird, but in my trying to learn, i am seeing some beams that are burning and the beam is actually changing diameter throughout. But others seem to have a more "perfect" beam almost like when you look at the beam of a 532 nm. I hope this makes sense. just trying to wrap my head around what will actually perform what way.




Again, thanks for the help.

dave

 

[Zeebit]

The PL450 is single mode while the PLT450 is multimode.

The reason why you are seeing a beam that is not uniform is because the diode is multimode meaning you get a rectangular output instead of an oval/circle from a single mode.

DPSS lasers produce the best beam profile, IMO.

 

[andrewb]

If you're talking pure 'visibility', then it basically comes down to power. The 9mm, PLT450, and M140 should all appear pretty much the same brightness if they're all at 1.5W.

However, if a bright beam is what you're after, get a 9mm 445 from DTR with an x-drive running at 2.3A, and the stock lens (informally called the 'G9' lens). He sells this as a combo on his website, for $125. This will give you between 2.5 and 3+ watts, depending on the efficiency of the diode. You'll light up the sky like a lightning bolt, and it'll be the brightest blue beam you can get for the money. I have one in a Saik 305 host, and I love it.

 

[The Lightning Stalker]

This is the exact same question you asked in the General forum.

 

[jeffreythe00]

Lets take a scientific approach to this.

Since there will be a lot of variables, lets eliminate them all with theory. Lets place the test in a perfect setting. Lets assume all the diodes are producing "exactly" the following.

(Diodes will vary in wavelength a bit from diode to diode. The wavelength will shift differently as well from diode to diode depending on what you run them at. Wavelength will also be dependent on temperature ect ect. I can go on and on You get the idea.)

In a perfect setting lets say these specs are "exact"

PL450 - 450nm @ 150mW
M140 - 445 @ 1.5W
9mm - 445 @ 1.5W

The PL450nm diode should (in theory) be relatively 1.22x brighter than the 9mm and M140 running at the same 150mW. The M140 and 9mm diodes are running at 10x the power of the PL450 so both of them would be brighter.

Now we have two "equal" diodes. The M140 and 9mm. They should be the exact same brightness in this theory right? Wrong. One more variable about this that nobody thought about was emitter size.

Let me explain. A larger emitter equals a larger beam. A larger beam equals less power density and lower relative brightness. Since the 9mm diodes can be run at higher current. In theory they should have a larger emitter which would result in a beam diameter. That would result in a loss of relative brightness vs the M140.

So there you have it. The M140 run at the exact power and wavelength as the 9mm should theoretically be brighter in the "very" slightest due to its smaller emitter.

This is all theory of course since I don't have the EXACT info on die sizes, beam sizes ect. However my point being that higher power density equals a brighter beam even if the two laser devices are the same in most areas.

It's the reason why if you focus your laser, you don't actually get a megawatt beam . The laser is still the same output. A 1.5W laser is still 1.5W focused.

Hope this helps.
Jeff

Relative brightness calculations were done with Beam: (450nm 150mw) vs. (445nm 150mw) _ Thanks RHD!

 

[Cyparagon]

Emitter size only matters at a distance. The focal length of your collimating lens determines the near-field beam size. In an aixiz arrangement, single-mode reds (that have a 1-2 micron emitter) have the same beam size as an A140 (with its 15 micron emitter).

 

[dweglarz13]

First off, thanks for that explanation. I do understand now, so Im learning now!
Its amazing all the little variables that can and will affect this. Getting closer to my first build.
It seems any one of these 3 diodes can give a better beam with just 1 or 2 factors changed a little. So, I guess for my first build, it really shouldn't matter all that much, but I do appreciate you guys helping me to understand it all. Now, time to learn about different lenses........

dave

 

[honeyx]

... as opposed to some beams I see that seem to be thick in some spots than more focused in others?

This is because like others already mentioned by having a mulitmode diode you are getting a rectangular beam profile. Depending on which angle or let´s better say from which side you are looking at this beam it either appears to be thin or thick.

So by looking at the thin edge it also appears to be a bit brighter because it´s looking like having a higher density though this is just going into depth.