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FrozenGate by Avery

Pumping Ruby using 8x diodes?

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pianoman2011

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Hey guys,

I've been busy this summer so I haven't been on LPF but I was reading Sam's Laser FAQ and saw this:

"DPSS Ruby Lasers? While this is theoretically possible, the absorption bands of ruby (404 to 554 nm) do not match any currently readily available inexpensive high power laser diodes. They are all in the infra-red range, mostly around 808 nm and 980 nm. The relatively high power visible laser diodes are very expensive and these are 635 nm and longer wavelength. I don't know how far it would be possible to shift the wavelength by cryogenic cooling (0.3 nm per °C) and that might create other problems. Perhaps once violet or blue laser diodes are developed in high power versions, this situation will change."


When Sam says 404nm, does he mean that it NEEDS to be exactly 404nm, or could one possibly use 405nm diode(s) to do this? How much power is he talking about? If "only" a watt or two is needed, couldn't one combine the light from an array of 8x diodes to make this setup possible? I WANNA SEE A DPSS RUBY LASER!!! :D

Sorry if this has already come up in conversation.

I'm especially looking for an answer from someone very knowledgable (like pullbangdead :cool:)
 





pianoman2011 said:
Hey guys,

I've been busy this summer so I haven't been on LPF but I was reading Sam's Laser FAQ and saw this:

"DPSS Ruby Lasers? While this is theoretically possible, the absorption bands of ruby (404 to 554 nm) do not match any currently readily available inexpensive high power laser diodes. They are all in the infra-red range, mostly around 808 nm and 980 nm. The relatively high power visible laser diodes are very expensive and these are 635 nm and longer wavelength. I don't know how far it would be possible to shift the wavelength by cryogenic cooling (0.3 nm per °C) and that might create other problems. Perhaps once violet or blue laser diodes are developed in high power versions, this situation will change."


When Sam says 404nm, does he mean that it NEEDS to be exactly 404nm, or could one possibly use 405nm diode(s) to do this? How much power is he talking about? If "only" a watt or two is needed, couldn't one combine the light from an array of 8x diodes to make this setup possible? I WANNA SEE A DPSS RUBY LASER!!! :D

Sorry if this has already come up in conversation.

I'm especially looking for an answer from someone very knowledgable (like pullbangdead :cool:)
Click to expand...

Yes, but you've got to consider that bluray diodes are not always 405nm, there's a +-5nm tolerance on them. If you're out for too many nm then you won't be able to achieve any power at all.
 
Yes, but you've got to consider that bluray diodes are not always 405nm, there's a +-5nm tolerance on them. If you're out for too many nm then you won't be able to achieve any power at all.
Click to expand...

So if someone like Mohrenburg, who builds (or used to build) a lot of violet lasers, bought a spectrometer and saved aside the diodes that were in the 402-406nm range, they could essentially save up enough diodes to create an array that could pump a ruby rod, and make a functional ruby laser using 405nm diodes?
 
I don't think anyone knows for sure, if this will work. It sounds like a worthwhile experiment since rubies are known to fluoresce with UV light. Whether it could be done DPSS style with a small rectangle of polished synthetic ruby or need to be a ruby rod with several diodes in an elliptical reflecting cavity is something that could be tried.
 
I don't think anyone knows for sure, if this will work. It sounds like a worthwhile experiment since rubies are known to fluoresce with UV light. Whether it could be done DPSS style with a small rectangle of polished synthetic ruby or need to be a ruby rod with several diodes in an elliptical reflecting cavity is something that could be tried.
Click to expand...

I say someone retired and with a reasonable amount of money should try it! I think I will myself once I check off a couple of things off of my laser to-do list, save some money, and get a lot more experience in the laser field. This problem still isn't resolved though :scowl:

-Jakob
 
The main issue you'll have is trying to run a ruby laser CW. Ruby heats up very quickly, so ruby lasers are always pulsed. If you pumped it with sufficiently large short-duration pulses from a 405-410nm diode array (405nm diodes can produce any wavelength between 395nm and 415nm depending on temperature) it would be very possible to pump ruby, but presently that's more expensive and complex than just flash pumping with krypton flashlamps, although that might change given the trends in the cost of blu-ray systems. You will always get more power per pulse out of a flashlamp pumped system than diode pumped, and the Hughes ruby laser rangefinder from the M-60 tank (a commonly found hobbyist laser) is easily capable of 50-100kW of peak instantaneous pulse energy output.
 
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Going off what ElectroFreak said:

Ruby is a self terminating 3 level laser. You can run it CW, but you need to use a different absorption band. There was just a product released for researchers which is a CW ruby DPSS system, however, they just got a patent on how to do it, I have read the patent, and it is not a easy concept.
 
Thank you Elektrofreak and Laser_Ben. Just one more question... what light source does that CW DPSS Ruby Laser use to excite the ruby?
 
Also, take into consideration that aligning lots of 8x diodes will not be an easy task. You can only use two if you're using a combiner.
 
This is a DPSS ruby laser 150mw and that is the "actual" beam shown in the picture.........


continuous-wave-dpss-laser-393090.jpg
 
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If it is, that's impressive.. I'm calling BS on that being the actual beam though. It just doesn't look quite right.
 
ElektroFreak said:
If it is, that's impressive.. I'm calling BS on that being the actual beam though. It just doesn't look quite right.
Click to expand...

You are correct. Look at the very entrance of the window, the laser is kind of "bigger" in a way that it looks like a semi cone. There is no glow around the beam and there is not even the minor scattering over the internal part of the window.

shopped.jpg
 
Yes it looks way too solid. And the color isn't shaded where it's lighter on the inside and fades out. Oh well, still an impressive laser...

-Jakob
 
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