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4mW of 473nm? Curious?

Hap

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Hey all,

As im sure most of you folks know about my 473nm pointer. It averages about 4mW of 473nm light and it's amazing, but I do have a question about it I still haven't quite found an answer to and am very curious to find it :)

Question:
Would you consider 4mW of 473nm light in a pointer hard to produce? Or is it relatively easy with today's technology?

-Alex
 

ultimatekaiser

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I wouldn't say its difficult... But it definitely inefficient, so therefore expensive, or at least more so than green. Most dpss is about the same difficulty to produce, variant on what parts are needed (LBO vs KTP etc.). But stabilizing them is a whole different story. 473 is far harder to stabilize & Yellow even more so because they get very hot , and each part has a different & very particular/picky thermal needs. So each part has to be cooled differently.
 

IsaacT

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How much wattage would be required from a pump diode to produce 4mW of 473? I understand there will be something of a range. 5% efficiency? Less? More?
 

ultimatekaiser

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All the cni pointers use 500 mW c-mount diodes I think. I've gotten about 30mw out of a 473 briefly, and about 3-7 of the yellows. Though very unstable from heat.
 

Hap

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I wouldn't say its difficult... But it definitely inefficient, so therefore expensive, or at least more so than green. Most dpss is about the same difficulty to produce, variant on what parts are needed (LBO vs KTP etc.). But stabilizing them is a whole different story. 473 is far harder to stabilize & Yellow even more so because they get very hot , and each part has a different & very particular/picky thermal needs. So each part has to be cooled differently.
Ahhh alright, I appreciate it kaiser. I do have one last question though. What exactly is meant by "coating"? I always though all you need to create 532nm/473nm/671nm etc.. was to just line up the crystals and boom, you have the wavelength?

-Alex
 
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ultimatekaiser

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Ahhh alright, I appreciate it kaiser. I do have one last question though. What exactly is meant by "coating"? I always though all you need to create 532nm/473nm/671nm etc.. was to just line up the crystals and boom, you have the wavelength?

-Alex
do you want the long or short answer? do you even know how a laser works? I'm beginning to think you might not. but in short, you in theory could just line them up and get a little coherent light, but real world losses wouldn't allow that. (this is called single-pass gain)

Think of a HeNe...the very model of how a laser works. a gas tube (the lasing medium) with a mirror on each end... a high reflector (HR) (99.99% reflective) and an output coupler (OC) (usually around 98.5-99% reflective). when you excite the gas in some manner, it gives off coherent light, this is then trapped between these mirrors, creating a pool of light at that particular wavelength desired, based on the properties of the mirror. however, one mirror is slightly less reflective (the OC) than the other, so light eventually starts to 'leak' out. that's how you get your beam.

This principle is called a Fabry-Perot or FP style cavity, and it is the most basic form of creating a laser.

your pointer is made based on this process. it starts with an 808 diode. this light then passes through the Nd:YAG which causes the Nd atoms stuck in the crystal lattice to fluoresce at another wavelength (946) however single pass isn't going to give you much as it passes through, and will result in mostly waste, so a mirror is placed at each end using the same principle as above to gather enough 946 to be useful. this is then allowed to pass through the LBO for its doubling. however again, we need more than one pass. so putting the OC before the LBO won't work. so it's put after, but we also need it to reflect 473. so the mirrors are then made to reflect that as well. and the LBO is coated AR to allow them to pass through with less reflections, allowing as much to be doubled as possible. the remaining 473 is allowed out the OC to be coupled by a lens and used by you, while an IR filter, catches the last stray IR photons.

however this is how it is done on an optical table. but to save space and cost since the pointer is so small, these mirrors are often coatings on the surfaces of the crystals, instead of separately mounted parts. this guarantees the surfaces are always parallel as long as the cavity is aligned properly (minus thermal expansion) with the OC. and saves space, as well as cost as you don't have to fabricate actual mirror substrates. they just apply them directly to the crystals. it also makes it simpler (relatively) to make.

you can use this pic for reference:

mirrors would be:
Nd:YAG: HR on first surface, AR last surface
LBO: (AR both surfaces)
OC lens is well...the OC mirror 'nuff said :)

*takes a breath* got all that? :D There's alot more to add, but that's the medium answer.
 
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Hap

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^Got it kaiser ;)

I appreciate you taking the time to explain all this to me, I really do! Alex still has much to learn lol.

-Alex
 

chipdouglas

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This is not the full truth for hene's.... a hene I believe makes all the wavelengths and as I've been told it is the final output lens that dictates the color. this is why a green hene's tube glows red. I could be wrong. but this is what I've been told a while ago.

edit... do you love my non-committal answer =p



do you want the long or short answer? do you even know how a laser works? I'm beginning to think you might not. but in short, you in theory could just line them up and get a little coherent light, but real world losses wouldn't allow that. (this is called single-pass gain)

Think of a HeNe...the very model of how a laser works. a gas tube (the lasing medium) with a mirror on each end... a high reflector (HR) (99.99% reflective) and an output coupler (OC) (usually around 98.5-99% reflective). when you excite the gas in some manner, it gives off coherent light, this is then trapped between these mirrors, creating a pool of light at that particular wavelength desired, based on the properties of the mirror. however, one mirror is slightly less reflective (the OC) than the other, so light eventually starts to 'leak' out. that's how you get your beam.

This principle is called a Fabry-Perot or FP style cavity, and it is the most basic form of creating a laser.

your pointer is made based on this process. it starts with an 808 diode. this light then passes through the Nd:YAG which causes the Nd atoms stuck in the crystal lattice to fluoresce at another wavelength (946) however single pass isn't going to give you much as it passes through, and will result in mostly waste, so a mirror is placed at each end using the same principle as above to gather enough 946 to be useful. this is then allowed to pass through the LBO for its doubling. however again, we need more than one pass. so putting the OC before the LBO won't work. so it's put after, but we also need it to reflect 473. so the mirrors are then made to reflect that as well. and the LBO is coated AR to allow them to pass through with less reflections, allowing as much to be doubled as possible. the remaining 473 is allowed out the OC to be coupled by a lens and used by you, while an IR filter, catches the last stray IR photons.

however this is how it is done on an optical table. but to save space and cost since the pointer is so small, these mirrors are often coatings on the surfaces of the crystals, instead of separately mounted parts. this guarantees the surfaces are always parallel as long as the cavity is aligned properly (minus thermal expansion) with the OC. and saves space, as well as cost as you don't have to fabricate actual mirror substrates. they just apply them directly to the crystals. it also makes it simpler (relatively) to make.

you can use this pic for reference:

mirrors would be:
Nd:YAG: HR on first surface, AR last surface
LBO: (AR both surfaces)
OC lens is well...the OC mirror 'nuff said :)

*takes a breath* got all that? :D There's alot more to add, but that's the medium answer.
 
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ultimatekaiser

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it lases all colors at once, the mirrors determine what wavelength is chosen. they're dielectric mirrors, and they change the reflective index to the wavelength desired. but theres alot of variables, such as gas pressure that come into play. note i didn't specify anything about wavelengths...i just was simply talking about the cavity construction though for the sake of a model to picture in his head.
 
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trencheel303

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bloompyle had a YouTube video that explains remarkably well the basics of how a HeNe works, and it's something I've remembered the basics of since I watched it.

I say had because I just looked at his channel, and I'm pretty sure it's him but all the laser videos have now gone.
 

ultimatekaiser

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yeah i havn't seen his in a while either.

I did one a long time ago too but its not posted here. I had to do it for a class at one point and explain in detail how it works. I'm quite well versed with HeNes since they've been around so long. and they're among my favorite lasers. just wish they weren't so fragile.
 
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KapHn8d

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I tried to rep you for that response ultimatekaiser, but apparently I need more spreading.

Cheers,
c
 




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