532nm modulation problem

[badger1666]

i am having modulation problems on my green
its fine cw , the problems start when you modulate it.
alot of beyond cues the green only just lights up others its ok with
now if i use a cue that it does not work with,and slow the scan rate right down it starts to work
but not that great.
so it works with cues that have alot of green on time but not with others that have little on time
but somthing like a cone of beams is fine so it ok at switching on and off fast enough
very confused as to whats going on , anyone have any ideas ???

thanks

[dilbert]

I just spent ages sorting a similar problem on my green which I was setting up the driver from scratch - When tuning I found the LBO had a number of peaks at different temperatures. If I chose the best for maximum CW power I had the same issue as the peak was very narrow & the TEC couldnt keep it in the narrow band under certain modulation. I tuned to a slightly lower peak with a wider band that the TEC had no problem maintaining and now problem solved, correct green in all cues. I would try a slight tweak on your crystal TEC pot. Beware tuning it can be a very time consuming process.

[badger1666]

to add , my 1w laser is a single tec design , its just come back from china for a general low power problem that its had since day one ,but it always modulated ok
now it does not
and i dont fancy the expense of sending it yet again for repair.

[White-Light]

Get one of Rob's colour correction boards Chris that way for £50 you can compensate it out.

[badger1666]

hey al as good as robs boards are i dont think they can compensate for poor xtal heat transfer.
update tweekd the tec temp now 90% of cues work, not to the power they should though.
i had noticed theres a long tail at the begining of the green, and a full power green cone flickers alot
says to me xtal has poor heat transfer to its mount
yes or no ?? any pros dpss guru's care to comment please

[dilbert]

The flickering means the temperature is varying a lot ( well lot by xtal terms ). You can probably solve by carefully taking time tuning or by improving the TEC driver.. Its possible the xtal has poor transfer to the mount but I'm betting the mount is changing temp too.

[White-Light]

You're probably right Chris, worth a suggestion though.

Main reason I made it is because I saw colour variation in the Kvant with cues which I put down to modulation. The green has now been tested and I'm told there's nothing wrong with it although it is being changed for something hopefully better. I believe the original green was a cni so maybe instability is something endemic in Chinese greens.

[badger1666]

tweeking the tec any more is not an option it at its lowest point, might pop the hood so to speak, and give the mount fixings a tweek and see if that helps,
or it try and find some indium foil and do a re shim on the xtal, sure cant make it any worse, wished i had done it in the first place instead of sending it to china for a service,and it coming back worse than it went, might just buy me a new one and hope for better luck, this ones been a bitch since the day i got it

The flickering means the temperature is varying a lot ( well lot by xtal terms ). You can probably solve by carefully taking time tuning or by improving the TEC driver.. Its possible the xtal has poor transfer to the mount but I'm betting the mount is changing temp too.

[badger1666]

update found the problem the Nd:YVO4 xtal needed a position tweek, took some fiddling to find the sweet spot.
so what i did was pop the hood fired it up modulating a green cue the laser did not like, loosened the xtal clamp gave it a prod with
a cocktail stick, and boom 350mw popped up on the power meter whoop whoop .
and it still bangs out 1w cw , there is still a bit of a delay on the green coming on , on just two cues ,but might just use whitelights
idea and try one of robs correction boards and see if can help the rest of the way :

[epyn]

Dear photonists!
Did you ever see something like this?
My greenie doesn't works properly at low brightness.
Chops the light independent from the scanning speed.There is no quickFX on the frame.
At full brightness this phenomenon is disappear or i just can't see .
The other two lasers aren't looks like the green.They works properly.
Does the power-supply unit cause this possibly?I use a quality FSP 350W PC ATX PSU.
The IR diode works from the 5V line.The blue and the red diodes from the 12V.
Ferenc