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Transverse modes in DPSS laser

RA_pierce

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I have collected a few different crystal sets for DPSS greens. While I was playing with them and my 808nm pointers, I thought, "I haven't seen any videos on the forum showing the TEM modes that these tiny crystals are capable of." So I made a video.

Normally we like to see the nice Gaussian profile of our laser beams, but the other modes are just as pretty. Mode shifts seem almost fluid and the peculiar shapes and patters that these beams make are fun to watch.

The first two crystal sets are from low powered pointers. The crystal set used to make the pictures and the last two video clips output about 60mW (when it was an X50).

I hope you enjoy.  :)

[media]http://www.youtube.com/watch?v=CzBf7bV80A0[/media]






 

ElektroFreak

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Very cool! This is one of the best demonstrations of TEM modes that I've ever seen.. and they definitely can be quite beautiful. I've kept some green crystals around and done this same thing myself.
 

Kenom

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Absolutely stunning video. It's like green fire in a few places and quite mesmerizing.
 

Morgan

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As I have only just ordered my first greenie I am grateful for this video. I don't yet know the beauty of 532nm light!

Am I to assume that this is SERIOUS mode-hopping? I have searched a bit for this but it is still a bit of a mystery. Is the ideal, (for a commercial pointer anyway), TEM00? Does this mean just one clean spot? Are the problems with mode-hopping just a matter of alignment? Any useful links? Wikipedia shows the patterns but I couldn't see WHY they happen.

I try to understand the answers to questions I ask and if there are threads explaining them then I've missed them and apologise for covering old ground. (I know how it annoys people.)

Thanks all,

M :)
 

ElektroFreak

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Morgan said:
As I have only just ordered my first greenie I am grateful for this video. I don't yet know the beauty of 532nm light!

Am I to assume that this is SERIOUS mode-hopping? I have searched a bit for this but it is still a bit of a mystery. Is the ideal, (for a commercial pointer anyway), TEM00? Does this mean just one clean spot? Are the problems with mode-hopping just a matter of alignment? [highlight]Any useful links?[/highlight] Wikipedia shows the patterns but I couldn't see WHY they happen.

I try to understand the answers to questions I ask and if there are threads explaining them then I've missed them and apologise for covering old ground. (I know how it annoys people.)

Thanks all,

M :)
Here ya go: http://www.laserpointerforums.com/forums/YaBB.pl?num=1234903304

http://www.laserpointerforums.com/forums/YaBB.pl?num=1226070525/0#0
 

Morgan

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ElektroFreak,

Thanks. I think that succintly answered all the questions in my post, but don't worry, I'm sure I can come up with more.  ;D

Good links though. I think it's important to understand at least some of the theory before I get my 80-100mW module. I feel it will stay in its packaging for a while until I can confidently attempt a build. Heatsinking, suitable power, etc...

Just let me see if I've got this bit of theory correct, (I'm pretty sure I've seen a thread with this info in but if it's in my head correctly without reference then I've learnt it, if you see what I mean):

Most crystal sets have two types of crystal. KTP and the Nd???, (nope that bit hasn't stuck just yet). The KTP is pumped by 808nm light to create 1064nm which pumps the Nd??? to frequency double it to 532nm. Correct?

If this is so, and it is possible to purchase 1064nm diodes, (I believe that HUGE auction purchase from Boston Lasers had some 1064nm diodes), why bother with KTP at all?

Thanks,

M :)

P.S. lovely vid of the green fire BTW.
 

ElektroFreak

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Morgan said:
ElektroFreak,

Thanks. I think that succintly answered all the questions in my post, but don't worry, I'm sure I can come up with more.  ;D

Good links though. I think it's important to understand at least some of the theory before I get my 80-100mW module. I feel it will stay in its packaging for a while until I can confidently attempt a build. Heatsinking, suitable power, etc...

Just let me see if I've got this bit of theory correct, (I'm pretty sure I've seen a thread with this info in but if it's in my head correctly without reference then I've learnt it, if you see what I mean):

Most crystal sets have two types of crystal. KTP and the Nd???, (nope that bit hasn't stuck just yet). [highlight]The KTP is pumped by 808nm light to create 1064nm which pumps the Nd??? to frequency double it to 532nm. Correct?[/highlight]

Just the opposite.. The 808nm diode pumps an Nd:YVO[sub]4[/sub] crystal which generates 1064nm light, which is then doubled by the KTP, producing 532nm photons.

If this is so, and it is possible to purchase 1064nm diodes, (I believe that HUGE auction purchase from Boston Lasers had some 1064nm diodes), why bother with KTP at all?

Direct doubling a diode is extremely difficult for reasons I won't go into here (very complicated), so generally you won't find a 1064nm diode directly doubled to 532nm..

Thanks,

M :)

P.S. lovely vid of the green fire BTW.
hope that helps..
 

Morgan

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Thank you Sir for the correction. :-[ As I err, I learn.

Yes, that helps.

More homework needed but I is learning. Honest! I find this whole subject of coherent light and all the associated science absolutely fascinating but I wanna know it NOWW!!! :(

Note to self: Small steps Morgan, small steps.

M :)
 

ElektroFreak

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Morgan said:
Thank you Sir for the correction.  :-[ As I err, I learn.

Yes, that helps.

More homework needed but I is learning. Honest! I find this whole subject of coherent light and all the associated science absolutely fascinating but [highlight]I wanna know it NOWW!!![/highlight] :(

Note to self: Small steps Morgan, small steps.

M :)

If you haven't already, read this: http://www.repairfaq.org/sam/lasersam.htm

It's very in depth, so reading all of it will take months, but it is the laser "bible" pretty much..
 

Morgan

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^I've certainly been there...

... And it is hard going! Sometimes a bit difficult to navigate too. What I have read there usually leads onto further research eleswhere and, due to a lack of pictures, I sometimes get lost. I'm a, "learn by doing", person mostly so the format isn't best suited. Don't do too well with text books either. :(

It is the number one place to verify or condemn an idea though, (other than asking relevant questions in a relevant thread here, of course!). I prefer a little interaction because if I don't, "get it", the first time, someone else may have a different way to put it. Never been involved with any forum before this one so am finding this experience a joy too. Photolexicon scares the cr*p out of me! Looks very serious over there and I feel too much of a minnow for the moment.

I try not to be lazy, so thanks for the pointers and I am reading the links. I'm sure they'll help others who are also informationally bereft!

Yours,

looking forward to building my first greenie!

M :)
 

Morgan

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^Thanks Lotus_Darkrose,

Yep, that's exactly the answer. After reading that section, I got sucked in to the site again and got lost!

However, that whole section will become relevant when I get my green module so I now have a reference point, on LPF, from which to dive.

That's why I find the site difficult. I start reading a topic; can't stop because the next bit is interesting too; an hour later, and I've forgetten why I'd gone there to start with! I know it is only me but it can get in the way sometimes!

Good to have all your back-up, and glad of all your patience.

M :)
 




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