Nd:YAG mirrors and optics

[Xenon1]

Hi everyone! So, I'm new to the community here, and just getting warmed up in the area of laser physics. I have a few questions about Nd:YAG lasers and homebrew resonator optics.

First off, I just purchased an Nd:YAG crystal, new in OEM packaging, 4.8mm dia. and 90mm length. Unfortunately, the only information that I was given was that it's suspected to be a replacement for use in Iridex (slash Laserscope?) laser system, I imagine 1064 nm for dermatology work. I haven't gotten far yet with finding further details, so I guess I kind of gambled here, as I don't have a figure for the % doping Nd, nor do I know if it has an AR coating. Reading Sam's article on homebrew systems and SS lasers in general, however, I remain optimistic!

Now, my question to all of you is this - how critical is the quality of the resonator's mirrors? I've seen Chinese mirrors - dielectric, BK7 material... however, they have a surface quality of 60/40 scratch-dig (which according to this page: Scratch-dig | Optical technologies is not so great!) and a flatness of L/4. The page I referenced here says that such a mirror may get by for "low power laser and imaging applications," but how critical is this for a YAG system that could reach considerable peak power, perhaps even as high as a MW? Has anyone actually purchased mirrors like this? 2 pieces of Nd:YAG laser reflect output mirror (1064nm) | eBay

Just as a side, has anyone here had luck in making a functional system from unknown Nd:YAG rods in a comparable size, and using reasonably inexpensive (I'm hoping <$50) flash tubes and optics? I'm beginning to appreciate just how expensive Nd:YAG systems can get!

Thanks so much!

 

[Bluefan]

I have bought two of those mirrors for a project, but that project has yet to start, so I can't say anything about them yet.
You already have the rod, you only need a flashlamp, cavity mirrors and the electronics. It's not stopping at your first laser which makes the hobby such a money sink.

 

[Prototype]

Quality mirrors are important. It's better to buy them ahead of time than get cheaper ones to start off with (if you can afford the better ones that is) because if you use them in a strong cavity, the mirrors won't withstand the abuse and you'll destroy them (nothing spectacular, just disheartening) and have to buy more.

 

[FrothyChimp]

Well your choice of Nd:YAG will make life much easier. Getting Nd:YAG to lase is far easier than some other rod configurations. I see the mirrors have a damage threshold of 500MW/cm^2. You now have a place to start your calculations. You will need to know the amount of energy your flashlamp will produce and the flash duration (should not exceed the fluorescence lifetime of the Nd:YAG rod), the expected absorption based on your reflector design for your cavity, the dopant level of Nd in the YAG (it should have a purple hue to it under normal lighting indicating a higher dopant level for flashlamp use), and the transmission of the OC mirror. You can calculate the expected resonator energy with this information to see if it exceeds the damage threshold of the mirrors. If so you may get one or two shots before the coatings give up the ghost. You will also need a small helium neon laser to align your media and mirrors. You didn't indicate whether the OC/HR is flat or concave which makes a difference as to the distance between the mirrors. It may seem a bit overwhelming but it is the engineering approach. As I mentioned, however, Nd:YAG really wants to lase so with a bit of trial and error you should be able to generate some coherent light but to improve the output will require a bit more. My assumption is you will be building your own pulse forming network? Mind the capacitor bank. It can kill you outright. Consider a bleeder circuit for extra safety and a voltmeter for visual confirmation of the voltage level of the bank.

 

[Xenon1]

I'm definitely up for the engineering challenge - I'm graduating from EE shortly! I just lack the experience in this field, so I'm looking for whatever direction/assistance I can get in determining the best options for this project. The pulse forming network, trigger, and HV supply shouldn't be a big deal. Incidentally, I have a rather sizable xenon flashlamp coming to me, 1000W. Bought it to play with my Tesla coils and whatnot, well before considering this Nd:YAG project. Somehow I suspect this would not be appropriate for the laser design, however

As it stands, I'm still waiting on the rod to arrive, so I won't have much of a chance to experiment just yet. I suppose I should just wait for the rod before I proceed with accumulating the rest of the parts, since it's the rod that I can't find any specs for (lack of info from the seller). I realized that there's a few local professors that might be able to help me identify it, as they specialize in coherent light applications. Maybe one of them can help classify it somehow? I wonder if one of them would be willing to install it in some of their equipment and energize it...

I think I'm willing to invest a bit more in optics if it's really necessary to keep this thing working in the long run. I've seen surplus/old Nd:YAG assemblies go for prices as low as a few hundred - I'll probably hit around the same level with something homemade if I buy even brand new mirrors. I just would like to avoid spending just over $100 for BOTH the OC and the HR individually

Thanks for all your comments so far, guys! Apart from what Sam's guide has to offer, are there any books in particular that you'd recommend for designing equipment like this? And FrothyChimp, as for the mirrors, I only know what the eBay auction told me, and the plano-concave ones they have listed also mention the radius of curvature. I was thinking of just getting flat optics - should I be taking another look into concave ones? I also just discovered that Newport sells optics - found the HR coated ones (05D20DM.10), now it's a matter of deciding how much transmission for the OC!

 

[FrothyChimp]

There is a huge list of books you could choose from for reference. Some of the more common one are:

Lasers by Siegman, Anthony (in depth, theoretical)
Photonics and Lasers by Quimby, Richard S. (General photonics, 2nd half is lasers)
The Physics and Engineering of Solid State Lasers by Kalisky, Yehoshua (theory and performance maximizing)
Solid-State Laser Engineering by Koechner, Walter (the motherlode!)

 

[diyssyag]

hey guys i am new to lasers but i had an interesting thought about diy optics.
iv found an old book about physics laboratory procedure and there was a section on mirroring glass objects with silver nitrate, ammonia, sodium hydroxide and dextrose.
i had two thoughts

1#
if i were to completely coat one end of my yag rod with silver and then partialy coat the other would a resonant cavity be created?

2#
if i was to spin a crucible of molten silicon dioxide until it formed a parabolic lens and then coated that in silver to create HR mirrors and an OC.

it seems apparent to me that option 2# would pose no risk to my rod whereas 1# might incur permanent damage

my rod measures 60x5mm and i have 2 coiled 40W xenon bulbs that i intend to pump it with.

just thought that i would share some ideas.
:lasergun:

 

[diyssyag]

oh thread is dead...

 

[diyssyag]

i think