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HELP ME !! TEMoo ??????

Sam UK

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Trying to find out what TEMoo beam mode is, Been looking everywhere and i'm struggling to find a defined answer. I have been looking for a hour and still lost on this. Can anyone explain to me about TEMoo beam mode ??
A short breif answer will be good for me.

Thanks guys and girls. :thanks:
 

Grix

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TEMoo is just a normal circle-shaped dot.
 

Gryphon

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^ Exactly

Theres a really nice graphic of a bunch of different output modes some where on this forum, i'll see if i can find it
 

Eudaimonium

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There is a graphic at Wikipedia, just type in TEM modes
You will see the difference of those right away.
 

ossumguywill

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how do lasers switch modes? I understand that most red diodes are single-mode, but what causes a green to go from TEM00 to TEM01?

will
 

ZRTMWA

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I'm wondering what could cause a laser to go into TEM34 mode. Anyone have any pics?
 

ElektroFreak

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Some lasers are intended to be multimode. Far greater power output is possible with multiple modes than just one, but having just one mode gives the best quality beam.

As far as "changing modes" or mode-hopping, it can be caused by a variety of things, but most frequently it is caused by the laser cavity changing shape minutely due to expansion from heating. In solid-state lasers (typically the most susceptible to mode-hopping) this is referred to as "thermal lensing".

A great way to investigate laser modes is to pump some laser pointer crystals with a 808nm diode and see (by running the output through a magnifying lens) what kinds of modes you can get . TEM34 can be seen while doing this, along with most other modes. Typically, the bigger the crystals, the easier it is to get some nice multi-lobed patterns.
 
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ossumguywill

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Some lasers are intended to be multimode. Far greater power output is possible with multiple modes than just one, but having just one mode gives the best quality beam.

As far as "changing modes" or mode-hopping, it can be caused by a variety of things, but most frequently it is caused by the laser cavity changing shape minutely due to expansion from heating. In solid-state lasers (typically the most susceptible to mode-hopping) this is referred to as "thermal lensing".

A great way to investigate laser modes is to pump some laser pointer crystals with a 808nm diode and see (by running the output through a magnifying lens) what kinds of modes you can get . TEM34 can be seen while doing this, along with most other modes. Typically, the bigger the crystals, the easier it is to get some nice multi-lobed patterns.

that's cool.
I always thought mode hopping had to do with some crazy quantum physics deal, but now I kinda want to mess with TEM modes.

will
 

ElektroFreak

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That's the simplified description. There are a lot of physics involved in the formation of emission modes, as the wikipedia article illustrates. With most green DPSS lasers the modes will follow a rectangular profile instead of a circular one as in the above illustration, although TEM00, 01, and 02 remain accurate. The reason for this is due to the gain medium being cuboid in shape rather than cylindrical. Nd:YVO4 (the gain crystal in most green DPSS lasers) is rectangularly cut, while Nd:YAG is always cylindrically cut, meaning Nd:YVO4 will always produce rectangular modes and Nd:YAG will always produce circular modes.
 
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ossumguywill

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That's the simplified description. There are a lot of physics involved in the formation of emission modes, as the wikipedia article illustrates. With most green DPSS lasers the modes will follow a rectangular profile instead of a circular one as in the above illustration, although TEM00, 01, and 02 remain accurate. The reason for this is due to the gain medium being cuboid in shape rather than cylidrical. Nd:YVO4 (the gain crystal in most green DPSS lasers) is rectangularly cut, while Nd:YAG is always cylindrically cut, meaning Nd:YVO4 will always produce rectangular modes and Nd:YAG will always produce circular modes.
Yeah, I looked at the crystals in some chinese green module I had and noticed they were cube shaped on the end. it looked to me like the beam edges might just get cut off before the circular lens. and Nd:YAG crystals are usually described as "rods". Thanks for explaining it simply, I find it's less useful sometimes to get the whole story than the abbreviated version.

will
 

Eudaimonium

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That's the simplified description. There are a lot of physics involved in the formation of emission modes, as the wikipedia article illustrates. With most green DPSS lasers the modes will follow a rectangular profile instead of a circular one as in the above illustration, although TEM00, 01, and 02 remain accurate. The reason for this is due to the gain medium being cuboid in shape rather than cylindrical. Nd:YVO4 (the gain crystal in most green DPSS lasers) is rectangularly cut, while Nd:YAG is always cylindrically cut, meaning Nd:YVO4 will always produce rectangular modes and Nd:YAG will always produce circular modes.
This one:
http://upload.wikimedia.org/wikipedia/en/b/be/Hermite-gaussian.png

THIS are the profile of all multimode lasers, I am not sure if circular are seen anywhere (expect intentionally created)
 

Eudaimonium

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Well I am still in solid states, I do not have any experience and not much knowledge of rods and gas lasers so was thinking of diode and DPSS lasers when I said that circular profiles are rarely seen.

Thanks for heads up anyway!
 




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