Old 05-12-2009, 10:53 PM #1
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Default Nd:YVO4 questions

So I just got my hands on a 3.5x3.5x6mm KTP crystal. I wanna use 2W or 10W 808nm. So what is the best Nd:YVO4 % that I should get? is 0.5% or 2% doped better? Is a 3x3x1mm 2% doped good enough for my project?


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Old 05-13-2009, 12:31 AM #2
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^From what I've read, I believe that you 'd want lower doping levels for CW operation and higher for pulsed operation. Check this section of Sam's for more info: http://www.repairfaq.org/sam/laserssl.htm#ssldps

Somewhere in that section is the info you seek..
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Old 05-13-2009, 12:36 AM #3
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^From what I've read, I believe that you 'd want lower doping levels for CW operation and higher form pulsed operation. Check this section of Sam's for more info: http://www.repairfaq.org/sam/laserssl.htm#ssldps

Somewhere in that section is the info you seek..
Bingo. Usually around .5-1% is a good level. It really depends on how much power you want to make overall. If you're going for big numbers, you want lower doping and pump the crap out of it. If you're only going for a few hundred mW's, you can get a higher dopant level and wont have to pump as hard.
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Old 05-13-2009, 04:53 PM #4
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Sounds like i should get that 2% 3x3x1mm one then
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Old 05-13-2009, 05:13 PM #5
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No.. you want the lower doping.. Unless you want lower output with less pumping. I'm pretty sure that for standard CW operation you want .5-1% like gooey said above.. Truthfully, you could probably make the system work well with either doping level, but for CW lower is better.
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Old 05-14-2009, 01:06 AM #6
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ive been looking at one of these also
http://cgi.ebay.com/ws/eBayISAPI.dll...m=260409085567
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Old 05-14-2009, 03:51 AM #7
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I would like to point out here that a lot more then just a diode, ktp, and YV04 is needed. You need a cavity for them, you need coatings on all the crystals, you need temperature controls, and you need an advanced knowledge of how it all works together.
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Old 05-14-2009, 01:37 PM #8
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Ya my crystals are coated. Im just slowly collecting parts. This project will take more research and months of work. I still gotta get a TEC and I have some lenses atm. Im just gathering everything possible and appreciate the help.
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Old 05-15-2009, 03:43 AM #9
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Ya my crystals are coated. Im just slowly collecting parts. This project will take more research and months of work. I still gotta get a TEC and I have some lenses atm. Im just gathering everything possible and appreciate the help.
I would recommend you get some mounts machined such that your KTP and nd:yvo4 are exactly aligned. As long as you have a clear path through them you should be able to get some sort of light, but more importantly is their orientation towards each other and the diode. You USUALLY want them to be pitched 45 from the diode, so that their 'points' run top to bottom, if that makes sense, but you want them to be square with each other. As long as the mounts have a tiny bit of movement you'll be able to get them aligned well. BUT the most important part, and the part that really needs to be on a precision mount, is the output coupler. If the output coupler is off by even a 10th of a millimeter it wont lase. It needs to be PERFECT. So spend a few bucks and get yourself a nice adjustable mount for it. Also, you probably want your OC to have an ROC of around 50-100mm.

If you are using a bonded crystal set you can ignore everything and just shine some 808 into it... lol. BUT, since you were asking about doping levels, I tend to think you are going with separate components. I'd shoot for around 1%, BTW.
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Old 05-15-2009, 02:53 PM #10
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Cool thx for the help. Ya i couldnt pass that 3.5x3.5x6mm high efficiency ktp up. Only $26 so im happy about that. Afew more quick questions. I get the corner to corner thing so can I put my open can diode right super close to the corner for efficiency? Also can I have my two crystal touching just like a DPM style? Also what do you mean by output coupler?
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Old 05-18-2009, 07:36 PM #11
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Cool thx for the help. Ya i couldnt pass that 3.5x3.5x6mm high efficiency ktp up. Only $26 so im happy about that. Afew more quick questions. I get the corner to corner thing so can I put my open can diode right super close to the corner for efficiency? Also can I have my two crystal touching just like a DPM style? Also what do you mean by output coupler?
I'll answer this in a couple hours... It's pretty involved
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Old 05-18-2009, 11:07 PM #12
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coolz
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Old 05-23-2009, 10:43 PM #13
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Cool thx for the help. Ya i couldnt pass that 3.5x3.5x6mm high efficiency ktp up. Only $26 so im happy about that. Afew more quick questions. I get the corner to corner thing so can I put my open can diode right super close to the corner for efficiency? Also can I have my two crystal touching just like a DPM style? Also what do you mean by output coupler?

Ok so here's the deal. If you use a bonded crystal set you can only get so much power. I think 200mW is about the maximum if you get a good set and pump them hard. The 'mirrors' on these bonded crystal sets are just coatings at one end of the ktp and one end of the vanadate (ND:YVO4). These 'coatings' are equivalent to flat mirrors, or mirrors without any radius of curvature. In the case of these tiny crystal sets, flat mirrors work becuase the cavity is so short that your energy density stays fairly high because the beam doesn't get much of a chance at all to diverge. Overall cavity length is only about ~2.5mm.

When you start using bigger components, such as a longer KTP and a thicker ND:YVO4, you can start making much more power. Unfortunately these do NOT come in 'bonded' sets with 'mirrors' (reflective coatings) built in (well, the high reflective mirror is built in, more on this later). The only coatings these larger crystals have are anti-reflective coatings to allow light to pass without losses.

So since these larger crystals will have a much longer cavity length, usually somewhere around 1-2cm on your 'averge' linear cavity design which can make up to around 500mW, your 1064nm beam (from the YVO4) will be able to diverge within the cavity and lose it's power density, which is bad for frequency doubling. The way to overcome this is to use an output coupler with a radius of curvature, rather than a flat mirror or coating. This output coupler allows 532nm light to exit, but it keeps the 1064nm light in the cavity to allow lasing to continue. ALso, since it is radiused, it focuses the light back down to maintain a higher energy density inside the doubling crystal. In this type of cavity design, you can still use one flat mirror. The flat mirror (or HR mirror) is built into the back of the ND:YVO4 in the form of a coating, much like the bonded crystal sets. It allows the 808nm pump light to enter, but is high reflective for 1064nm and 532nm, forming the high reflective end of the cavity.


I hope that helps!!! The hardest part about this kind of cavity is getting your output coupler aligned. It is VERY VERY VERY VERY VERY sensitive and requires some sort of precision adjustable mount.

Oh yeah, you do not want your crystals touching. They should be spaced apart. By corner to corner, I just mean that you USUALLY want your crystals tilted 45 degrees from the plane of the pump diode.

What kind of diode do you plan on using to pump these? I can tell you now that the KTP you have may be a bit too big for the power you are wanting to make. I mean it will still probably work, but something like 2x2x4mm might be better. Those big KTP's are meant for making a lot of power, and if that is your goal you are going to need a much more complicated cavity design.

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Old 05-23-2009, 11:50 PM #14
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That is more helpful. I bought this ktp
http://us.ten.ebid.net/perl/auction....735&mo=auction
and I was thinking now maybe about getting this as well
http://cgi.ebay.com/ws/eBayISAPI.dll...m=180357469092
Think this would be good?
Also do you know of any pictures of the set up or could you draw me a very crude picture of the crystal and lens set up?
Thank for any help.
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Old 05-24-2009, 12:56 AM #15
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If you bought that diode setup, you're looking at a much more complicated design, because you're going to be dealing with a lot of power. You probably wont be able to get away with a simple 'linear' cavity. You'll want to build at least a "v" cavity (there is a better name for it... cant recall right now) and really should build a z-fold. These are much more complex but have potential to give you a killer laser.

Also, those crystals probably don't have a high reflective coating on the back side. So you'll also need a high reflective mirror which needs precision alignment.

If I were you, I would buy a simpler crystal set and build yourself a nice linear cavity laser before you decide to tackle the bigger power green.

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Old 05-24-2009, 03:09 PM #16
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I bought the ktp a while ago already. Would that 20W at least be able to be handled by the crystals mentioned?
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