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Laser beam resonance.

mrgoogfan

mrgoogfan

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I have a 250mw toplaser e1 that puts out about 275mw. Anyaway, i noticed when the beam isn't collamated, the square [yes square] beam has changing interference patterns, exactly like the youtube video below. after a while when the laser gets warm the patterns steady, so it seems they are affected by temperature. Anyone else notice this?

YouTube - Cymatic experiment

Also, hi! I'm a new member but i've been browsing this site for months. I plan on buying a 1w dpss 532nm laser in a few months.

Check out my website too! I love to build things and my site has a crapload of cool stuff on it.
 





daguin

daguin

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mrgoogfan said:
I have a 250mw toplaser e1 that puts out about 275mw. Anyaway, i noticed when the beam isn't collamated, the square [yes square] beam has changing interference patterns, exactly like the youtube video below. after a while when the laser gets warm the patterns steady, so it seems they are affected by temperature. Anyone else notice this?

YouTube - Cymatic experiment

Also, hi! I'm a new member but i've been browsing this site for months. I plan on buying a 1w dpss 532nm laser in a few months.

Check out my website too! I love to build things and my site has a crapload of cool stuff on it.
Click to expand...

Your laser is either mod hopping or was multi-modal to begin with.

It is shifting between some of these modes

25371d1264832940-looking-build-laser-read-me-tem_modes.png


As long as you are happy with it, no problems. I have several HeNe's that shift modes as they warm up. The patterns can be quite interesting

Peace,
dave
 
E

ElektroFreak

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What you're seeing are the laser's resonator modes. They're called transverse modes..

The modes randomly changing is called mode-hopping, and in most cases it's not desirable. The vast majority of laser pointers are intended to be single-mode, which is a single round spot, brighter in the center than on the edges. This is referred to as TEM00 mode. If you recently bought the laser, I'd consider a return. While modes can be fascinating and cool to look at sometimes, with green laser pointers it's considered a defect if it's constant.


Transverse Laser Modes

Transverse mode - Wikipedia, the free encyclopedia

EDIT: Dave, ya beat me to it..
 
mrgoogfan

mrgoogfan

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I know what TEM modes are and I don't think it's mode hopping. Then patterns look nothing like the TEM modes. They are much more like the ones in the video. Not parallel/horizontal but staggered/honeycomb like.
 
daguin

daguin

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mrgoogfan said:
I know what TEM modes are and I don't think it's mode hopping. Then patterns look nothing like the TEM modes. They are much more like the ones in the video. Not parallel/horizontal but staggered/honeycomb like.
Click to expand...

The light is passing through a round lens, distorting the "ideal" shape of the TEM you see in the picture.

Either that or bees have taken up residence in your laser

Peace,
dave
 
mrgoogfan

mrgoogfan

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daguin said:
The light is passing through a round lens, distorting the "ideal" shape of the TEM you see in the picture.

Either that or bees have taken up residence in your laser

Peace,
dave
Click to expand...

No lens is used though. This is straight from the ktp.
 
daguin

daguin

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mrgoogfan said:
No lens is used though. This is straight from the ktp.
Click to expand...

Then it is surface distortion or the bees. I'm betting on the bees at this juncture

Post a picture or video. I'm sure it doesn't actually look like sand vibrating on a surface.

It's mod hopping, dude

Peace,
dave
 
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BKarim

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the Nd:YVO4 is squared but the pumping beam and resonnant cavity mirrors are round... this the same in the video: the plate is squared, but the vibrator is round

mode hoping is due to big size of crystals (so there are reflections between transverse faces that are resonnating) and to the fact that their efficacity (for example amplification gain and thus modes that can lase) is a function of temperature . maybe your laser lacks a good temperature control, but i am not an expert
 
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photonaholic

photonaholic

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An experimenter who digs Anoles... COOL.

Welcome!

We have an Anole, she has been around 4 years already.
 
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