mode hopping

[charleytown55il]

can anyone tell me if it looks like these following pictures are showing mode hopping? :-?

 

[charleytown55il]

one that looks normal

 

[me_too_lazy]

you dont have goggles?

 

[LarryQ]

That does look strange....But I don't know if it is indeed mode hopping

I don't remember ..but If it is mode hopping It could be the first sign your Batteries are giving up the ghost.

Put in a new fresh pair, and then re-check it.

LarryQ

 

[Nordhavn]

A picture cannot tell us if it's mode hopping per say.

The first one is no longer TEMoo and starting to become TEMo1. If it's like the second one then dims slightly looking like the first image in a flickering fashion then that's mode hopping.

 

[o_DEATH_ANG3L_o]

What laser is that? If the transverse mode is TEM00 then I am unsure what that is then. :-?

 

[charleytown55il]

its a x65 from nova laser.

Nordhavn, it did not start out fine then flicker to the wierd dot. it would be wierd when i turned it on. it would stay wierd until i let go of the button. turning it on again would fix it. all i can say is it is strange. :-? :-? :-? :-?

 

[Nordhavn]

So when it's warmed up it's ok?

How long do you have to have it on (in non TEMoo mode) before you can turn it off then back on running in TEMoo mode?

A simple current adjustment can optimise this for you so no fussing around is needed.

 

[charleytown55il]

QUESTION ONE: it did not seem to matter, although, i put fresh alkilines in and have not had a problem. i had ni-mh batteries in when i had the problem.

QUESTION TWO: it did not matter. half a second, ten seconds, really doesnt matter

 

[Nordhavn]

The nimh will provide about 2.5v for two cells vs. 3.1 for fresh alkalines. Use the alks for a while and see if the hopping returns as the voltage falls. This is typical with unregulated dpss lasers running close to margin.

 

[Gazoo]

I posted graphs in another thread. The laser is very well regulated and fresh batteries should not cause mode hopping or anything else strange to happen. I have not run mine down to the point of seeing mode hopping.

http://www.laserpointerforums.com/forums/YaBB.pl?num=1192227112

 

[charleytown55il]

so far, on fresh alkalines, its been fine. im charging the ni-mh batteries and will try them again.

 

[Nordhavn]

LOL regulated in what way?

That graph shows ~40% swing over the period of time.

That's enormous!

 

[Gazoo]

LOL regulated in what way?

That graph shows ~40% swing over the period of time.

That's enormous!

It is normal with a CNI. The reason for the change in power is the temperature of the laser. As the laser heats up the power falls off. If you notice, there was very little difference between the batteries I used...so it is well regulated.

The difference of output power where the graph starts at 110mw's and where it peaks at 125mw's is not 40%.. The time I ran it was appx. 90 seconds, maybe a little more. Nova recommends a duty cycle of 90 seconds on with this laser.

 

[Nordhavn]

The difference of output power where the graph starts at 110mw's and where it peaks at 125mw's is not 40%.. The time I ran it was appx. 90 seconds, maybe a little more. Nova recommends a duty cycle of 90 seconds on with this laser.

The graph shows it dipping much lower than 110mW. The laser most definitely is not regulated. Matter of fact no pointer is. The driver may be regulated to have a tolerance with differing battery chemistries but regulated output is not going to happen. For a DPSS it requires so much ancillary hardware that it's not practical. Brute force (Hercules) is the only way to achieve more stable power but it will never match that of a truly stablised lab laser.

 

[charleytown55il]

thats because the laser is over heating. i know the the duty cycle of the x-series is 100 seconds. it looks like it is droping at 150 seconds, so i think it is too warm to output enough light.