Welcome to Laser Pointer Forums - discuss green laser pointers, blue laser pointers, and all types of lasers



Question about 808 used to be 532

Fundles

New member
Joined
May 19, 2019
Messages
24
Points
1
So I have/had a junk 301 532nm laser. It was mode hopping like a boss. I lost the expansion lens getting the crystal set off. Now I have a decently focused 808nm laser.

My question is: should an 808nm laser burn better than it did when it was a 532?

Because this one doesn't, it seems a bit worse, although it still burns, my other 532 seems to burn better. What gives?
 



paul1598419

Well-known member
Joined
Sep 20, 2013
Messages
16,269
Points
113
The 532nm is a solid state laser that is pumped with an 808nm diode. The beam is much tighter than the pump diode's beam. You should be able to focus it to a fairly small spot, but nowhere near as tight as the DPSS laser's beam. It is more powerful than the 532nm one, but power isn't everything.
 

kecked

Active member
Joined
Jun 18, 2012
Messages
451
Points
43
It was the 1064 that did the burning. 808 isn’t as well absorbed in materials as 1064. 532 isn’t much of aburner
Try aligning the crystal back in again
Wear eye protection!
 

Alaskan

Well-known member
LPF Site Supporter
Joined
Jan 29, 2014
Messages
11,777
Points
113
I'm restating some things already posted in this thread a bit differently, my thoughts have been they aren't good burners due to the wide striped output most pump diodes have as well as the relatively long wavelength to the diameter of the collimation lens producing a beam which won't focus down to a small high power density point. I didn't know part of the reason was also due to absorption of that wavelength being poor to some materials, or the common stuff we like to burn, until this thread. Maybe I don't have all of this correct, comments?

I know one thing though, a high power FAP800 will burn well, lots of power and the ability to focus the fiber combined power to a tight point with that device. The fiber combined output beam characteristics is probably why those burn so well just as much as the amount of power with that beast.
 
Last edited:

kecked

Active member
Joined
Jun 18, 2012
Messages
451
Points
43
while the answer I gave is pretty short it's almost right. Here's a little more and if you want the full answer I'll point to the right material
Let's start with color. What color is a green ball? it isn't green at all. It reflects green so we see green so if you hit that object with green light most of it will be reflected. So then say that same object absorbs red light. If you hit it with red light it will absorb more of the energy. That doesn't mean that is the best color to hit it with. That depends on the material and every material is different. In general organics absorb more in the infrared than in the visible up to around 400nm than UV kicks in with a different set of effects such as the photoelectric effect, dna damage...etc... So for most stuff you want to play with 1064 is a good place to start. 10.6um CO2 is a very good place to start but I'm not going into the details of this. Look up rotational and vibrational excitation of molecules.

Ahhh but you say it will heat up then...well not so fast. He's the part I left out. How well does it conduct heat? How much mass is there to absorb the energy.

If the object is massive and has good heat conduction than even if you hit it with the most absorbed frequency it may have such a large reservoir and be able to dissipate the energy so fast that you can't heat it quickly. The burning we see is generally because we can deposit energy faster than the object can disipate it to the rest of the mass.

There is a lot more to it than I just gave you but that should give you the basic concept without math and quantum mechanics.

Summary: use IR or UV the 600-500nm range is less effective for most object around us. Bet that's why our eyes are adapted to see this light as it is best reflected. Never thought about that before. Makes sense.

AND Alaskan is also correct in terms of focusing light. the more you energy you can put in an area the better chance you can deposit the energy faster than it is dissipated. shorter wavelengths focus better up to a point. haha

a little deeper...why des fire burn...? no not the oxidation part but the thermal part. look up what radiant heat means...its IR.

I forgot a detail. The shorter the wavelength ie blue is shorter than red, the more energy per quanta of light. so if two objects can absorb both blue and red equally, and the spot is focued to the same size, and , and ....all being equal, the blue wil put more energy on the same surface area than the red. Be careful to take into account all those ands I left there. That doesn't mean blue will heat faster or better. Look at the full picture.
 
Last edited:

Fundles

New member
Joined
May 19, 2019
Messages
24
Points
1
Great read keck thanks for putting all that into perspective. Pretty sure the expansion lens is gone forever so it's an 808nm laser unless I can either find the lens or successfully remove the KTP for a 1064nm laser... but I'd imagine that would need the expansion lens too.
 

Alaskan

Well-known member
LPF Site Supporter
Joined
Jan 29, 2014
Messages
11,777
Points
113
Yep, turns out keck has a lot of knowledge, I appreciate it too. Don't forget Paul also gave you some input. Have fun!
 

Fundles

New member
Joined
May 19, 2019
Messages
24
Points
1
Yeah thanks to Paul and Alaskan too, kecked typed out an essay tho. 🤣
 

Alaskan

Well-known member
LPF Site Supporter
Joined
Jan 29, 2014
Messages
11,777
Points
113
I liked the the mention of the photoelectric effect, where UV has far more energy than long wavelengths. I've been studying quantum theory history up to where we are with it now, in laymen terms.
 

kecked

Active member
Joined
Jun 18, 2012
Messages
451
Points
43
Just to be clear. I’m a fool compared to Steve on this stuff.
 

paul1598419

Well-known member
Joined
Sep 20, 2013
Messages
16,269
Points
113
Just because the shorter wavelengths carry more energy does NOT mean they burn better. This is because 1 watt of 405nm is the same as 1 watt of 660nm light. There are fewer photons necessary to make 1 watt of 405nm light, but it is still 1 watt. That and the power density are the most important issues when it comes to burning items that absorb heat the same from these wavelengths.
 

kecked

Active member
Joined
Jun 18, 2012
Messages
451
Points
43
How that energy is absorbed and how fast it is absorbed play a large part. I wish it was just one thing but it’s a series of systems.

You are correct to point out energy density vs wattage vs flux. Three related but different concepts. How much does a pound of feather weigh compared to lead bullets....in the same gravity well.😭. How many of those feathers can fit in the same space as one bullet. Etc. the analogy is falling down so I’ll stop.

Fun to talk about and share. Does anyone else have a related topic or another point of view. I’m no genius either.
 

Alaskan

Well-known member
LPF Site Supporter
Joined
Jan 29, 2014
Messages
11,777
Points
113
From what I gather, the smarter you are, the less you believe yourself to be so.
 

kecked

Active member
Joined
Jun 18, 2012
Messages
451
Points
43
Maybe but my objective is share learn care. It’s not about me. My ego is of no matter. If I can help then that’s what I’ll do.
 




Top