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Modehopping?

freshert

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My new DX150mw baton style has a oval shaped dot. Does that mean its modehopping? It can light matches in under a second when its focused for burning... :-?
 

Murudai

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How 'oval' are we talking here?

Can you shine it through some glasses (side part, don't shine it through the front as you'll mess it up) and see if you can see two little dots? If so, it's mode hopped.
 

diachi

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Shine it through a convex lens, not all glasses will work as good, so your better off with a nice strong lens .

Diachi
 

Chad

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Keep in mind that there's a difference between mode hopping and running in a mode that isn't TEM[sub]00[/sub].  ;)  If it's just an oval shaped dot, it's probably what some companies call "Near TEM[sub]00[/sub]" - something that could be classified as either TEM[sub]00[/sub] or TEM[sub]01[/sub].

Get some goggles, defocus the unit, and shine it at a black target... if you can see 2 dots, it's TEM[sub]01[/sub].
 

freshert

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Chad said:
Keep in mind that there's a difference between mode hopping and running in a mode that isn't TEM[sub]00[/sub].  ;)  If it's just an oval shaped dot, it's probably what some companies call "Near TEM[sub]00[/sub]" - something that could be classified as either TEM[sub]00[/sub] or TEM[sub]01[/sub].

Get some goggles, defocus the unit, and shine it at a black target... if you can see 2 dots, it's TEM[sub]01[/sub].
Thanks for that little piece of info. I'm getting my goggles tommorow from optotronics and ill see if its modehopping. What would be the difference in power with a perfect tem00 and a near perfect tem00?
 

Murudai

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Nah freshert, that doesn't look mode hopped to me.

The oval might be a side effect of the fact that the laser is focusable, who knows :-? Or probably just near-TEM00 like Chad said.
 
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Seems like its just an elliptical beam profile. All of these lasers are at least a tad elliptical, but usually not horrendously bad. That pic really doesn't look TOO bad, though it definitely leaves room for improvement. Then again, I'm not sure I'd be expecting any better from a DX laser anyway ;)

Mode hopping isn't really the exact term for what we're talking about so a google search might not lead you to answers, but the misnomer caught on strongly in the laser hobbyist community. What we're referring to is the laser randomly switching between different transverse output modes. I'll let you look up what those are on your own though :p
 

freshert

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Murudai said:
Nah freshert, that doesn't look mode hopped to me.

The oval might be a side effect of the fact that the laser is focusable, who knows  :-? Or probably just near-TEM00 like Chad said.
Thats great to hear :) Would of been really bad if it was. If I RMA it the new one probably wouldnt get to Australia fast enough.
 

freshert

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laze_doctor said:
What exactly does modehopping refer to? I tried googling it, but no luck.
Modehopping only affects DPSS lasers (I think). It's when the dot is not one dot. Like a dot becomes two dots instead of one. For a better explanation ask one of the pros :-[
 

Chad

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freshert said:
[quote author=laze_doctor link=1213706954/0#7 date=1213708574]What exactly does modehopping refer to? I tried googling it, but no luck.
Modehopping only affects DPSS lasers (I think). It's when the dot is not one dot. Like a dot becomes two dots instead of one. For a better explanation ask one of the pros :-[[/quote]

Mode hopping refers to when a DPSS laser switches from one tranverse mode to another... Look at the Wiki for a diagram.
They switch modes because of crystal defects and changes in temperature, mostly.
 

freshert

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This laser IS modehopping :'( Only for a split second though, when its cold. Burns great after that split second. :p
 




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