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Ultra Lasers 120mW Mode Issues

plexus

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Dec 9, 2007
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I bought an Ultra Lasers 120mW laser pen. Its your typical looking laser pen but with a nice finish. Anyway, its my first 532nm DPSS pen, before that i've only owned NeNe's. After playing with the laser a bit I noticed some things and I wanted to get sense of this from you guys in order to determine if my laser is working properly.

When the laser is cold, at room temperature, and i turn it on, the beam seems to be in TEM01 mode (two lobes). I can see this when i put a spreader lens in front and cast on the wall. After about 60 seconds it gets more into a TEM00 mode. I find that i have to turn it on and off to get it to switch out of what appears to be TEM01. It will work in TEM00 mode for about 30-40 sec and then switch back into TEM01 mode. if i turn it on and off it start out in TEM00 and move to TEM01 in less then a second.

Is this typical of your average non TEC non temp regulated green pens?

i dont have any way to measure the output but i can tell you that when in this TEM01 ish mode it wont burn tape or the palm of my hand. but when its in TEM00 ish mode it will burn tape and the palm of my hand.

the test i have been using to determine if its operating ok is to shine it into the palm of my hand and observe both the brightness level of the reflection onto a table and the speed at which it burns.

i made a youtube video of this here [i cant post links for some reason so you will have to search for it, the title is Ultra Laser 120mW DPSS Green Laser Pointer Mode Change]
thanks!
 





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My dx200 laser does that exact same thing when its cold. its becaus of the crystal assembly being very sentitive to temperature now if its supost to do that i dont know. I know my alpha does not mode hop when its cold but my Dx does. this is just becaus of the quality of the laser but other than that i am pretty shure its ok for it to mode hop when its cold. next time try to warm it up in your hand or pocket for a few min before you turn it on and see if it does it then
 

plexus

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Dec 9, 2007
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yes, after the laser warms up it will do TEM00 fine for about 30-40 seconds and then go back to mode bouncing to TEM01. i guess this is one of the downfalls of making such a laser in such a small and non-temperature regulated format.

i guess i need to measure the power output of my laser.
 

ixfd64

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Sep 12, 2007
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I've never heard of Ultra Lasers before. Could you post a link?
 

plexus

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Dec 9, 2007
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it irritates me when people casually state things like "i think they got a bad review" without doing research to back up what they say.

anyway, they got a GREAT review and thats why I bought it. I bought it directly from the brother of the guy that owns the company that makes them.

ps. why cant i post links? very annoying. so i cut and pasted the review from candlepowerforums here:

07-05-2007, 01:58 AM
Lew Fong
Enlightened

Join Date: Feb 2007
Posts: 64
Shanghai Daheng DHL GB-100 100mW 532nm Laser Pen - Eval Report
Hi Folks,

I was fortunate enough to secure a small quantity of very-high quality 100+ mW, 532 nm DPSS laser pens made by Shanghai Institute of Optics and Fine Mechanics ( Shanghai Daheng Optics and Fine Mechanics Company, Ltd.), model DHL GB-100. These are the finest quality laser pens I have seen so far at any price, and represent the upper limits of what is possible given the state of the art in 12mm DPSS lasers, in my humble opinion. I recently distributed four of these units to the CPF membership, and am expecting further review and input from those members after they have had a chance to look them over. I am not a dealer of laser pens, but I do integrate the units into OEM devices that I manufacture. The intent of this article is simply to offer an impartial technical appraisal of the unmodified devices as-built.

All of the units I purchased measured anywhere from 102 to 120 mW peak on my Coherent Lasercheck. Peak power is achieved after only 5 seconds typically from a cold start, and maximum continuous operating time is specified as 45 seconds. Power de-rates gracefully to about 10-15% below maximum on average at the highest operating temperature. In intermittent operation, the proper ON/OFF ratio appears to be about 1:4 to keep the output power in the high-power portion of the power vs. temperature characterstic curve. I have not tried thermo-electric augmentation yet.

I know that many of you collect lasers for the challenge and fun of modifying and tweaking. This unit is not one to experiment with for two reasons: First, there is no advantage in doing so. The units are already peaked for maximum performance right out of the box. Secondly, the units are built so solidly that it is extremely difficult to take them apart. I sacrificed two of mine in the name of science and good old-fashioned American reverse-engineering, only to discover that there is no way to peak them any further. The pen barrel has a really nice pearl-grey, deep gloss finish with gunmetal-chrome trim and pocket clip. I had no other choice than to destroy the pen barrel by cutting in two different places with a miniature pipe cutter to access the laser module. I have taken a lot of laser pens apart. Unless you are very skilled and very careful, you will be lucky to still have a working unit if you try to take this one apart. Trust me on this! (yes, I have a dead one).

Quality of the units is evident in every aspect of the laser assembly. For example, there is a locking set-screw to fix the LD in place after factory alignment, rather than the typical spin-on lock ring that inevitably moves the LD out of the optimum position during tightening. The focus barrel and LD holder threads are tight and were cut accurately. The MCA input and output lenses are K-9 glass, as is the objective lens. The unit is well filtered against infra-red emissions, and produces nearly all of its output power at the 532nm line. The alignment of the optical components is such that the output beam is nearly perfectly coaxial. Alignment of the LD is already optimized in the X-Y and rotational axes with respect to the large (2.5mm?) MCA. The PCB is well supported within the pen barrel by a plastic shoe that fits snugly around the board, flush to the inner surface of the pen, to prevent damage by pushing the ON button too hard. There is a potentiometer on the PCB, but it is already set for optimum performance and efficiency. Advancing the control only increases current consumption of the regulator without increasing output power. However, power may be reduced with this control. I was able to reduce power as low as 45 mW before experiencing mode-ing on most units. One must use care not to short the control to the case during adjustment....this will cause instantaneous destruction of the laser diode. (yes, I ate one).

Quality of the product extends to the driver board as well, which is beautifully silkscreened and conformally coated....a really nice job for such a small PCB. The regulator circuit is reverse-voltage protected by a diode in series with the battery supply, and current regulation appears to be achieved with the popular current-mirror method. There is no optical feedback or other APC circuit, so the driver holds the LD voltage and current constant over the entire duty cycle. Surprizingly, output power stability is quite good, which I attribute to the design of the MCA/optical cavity and LD holder. The design offers a much more effective heat-sink for the LD and MCA than other designs I have seen, somewhat dampening the effects of heating upon output power. The assembly draws about 650 mA of current from a 3VDC source ( two AAA Lithium photo-type cells). Considering that the unit dissipates nearly two Watts in operation, it is amazing that output power stability is as good as it is, given that there is no optical feedback. It seems clear that the designers chose to address the problem of power stability at it's source - heat management - rather than to build a more complex, less efficient, and more expensive optical feedback topology. Lifetime of the laser is rated at greater than 5000 hours, and may perform well beyond that due to the effectiveness of heat transfer from the LD and crystal assembly. In addition, the LD itself is a 9mm type rather than the 5.6mm cans typically found in lasers of this power class.

Beam characteristics are excellent, with diameter <<1mm and divergence at <1.2 milliradians. I have not determined the coherence length of the beam nor investigated the unit's suitability for holographic purposes, but it is obvious even by visual inspection that the units exhibit very low-noise for the type, and may be useful for holography or other lab work. This is an extraordinary statement to make about any DPSS laser pointer, as many of you will already understand. As I said, I believe that these units are the best available in a 12mm laser pointer. (Why can't America produce something as good?)

The pens are available at retail in the US from ultralasers.com, and can be found on eBay by seller shawnwang. I am curious to know if other CPFers have gained experience with these units yet, and what your impressions and observations have been, so please add your comments!

Cheers All,

Lew
 
C

Chris.

Guest
It mode-hops hence not that great. Nuff said.
Sounds like that reviewer was trying to get free stuff IMHO.
 

plexus

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name a laser pointer pen in a 12mm diameter format without external heatsinks and/or TEC that doesnt mode hop?

for what it is and what it does, its amazing. and after having it apart I can attest to the high quality of the design.

It appears from what I have been reading that anything above about 30mW maybe 50mW in a pen type design will exhibit some degree of instability. 120mW is really pushing for this kind of packaging.

It would not be fair to compare these lasers to TEC cooled packages.
 

plexus

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can you post a link to a review of the x125 that discusses its mode behaviour? also that discusses the nature of the cooling design? that would be useful. thanks!
 
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pen lasers (at least good ones) should not exit TEM00 within a reasonable duty cycle of around a minute or two, stability should not be a really huge issue, however 120mw is around the max for pen sized lasers. simply put - your laser is defective.
 

plexus

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really? ok but just to be clear... after the laser warms up from around room temperature it will work in tem00 mode for about 40 seconds and then hop to tem01. then if it cools down for about 60s it will give me another 40s of tem00 before going to tem01.

does that sound defective?

thanks for your help
 

Gazoo

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Yes, it is defective. I have a Nova X105 and it doesn't mode hop at all. A well designed laser will not mode hop. It doesn't matter if it is a pen laser, lab type laser, or just a module.

As far as Lew Fong... I would be a little weary of his reviews. He seems to have hidden agendas, for lack of better words. And I have read up on his posts at CPF.
 

Benm

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I'd say it IS defective and should be replaced. Modehopping in unusual circumstances is not unusual (very cold, amost dead batteries, etc), but when operating from good batteries in room temperature, it shouldn't hop modes like that.

Even cheap pointers like the ones from dealextreme don't normally have these problems, though the can have plenty of others.
 

Rhith

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I have a CNI pen and two different DX lasers and have yet to see any of them mode hop even the slightest bit. There are many slight variations in manufacturing that could cause this but for how much you generally pay for a handheld laser of that level it should be fully compliant to staying within TEM00 within normal bounds unless pushed to extremes. I would just try and contact the company and see if they will do anything about it. If not it should give a cool effect in a spirograph when in TEM01!
 

plexus

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well what the manufacturer specs is what i am getting: 120mW peak within 20 sec and 45s/60s duty cycle. but then you guys are telling me its defective. but then when i read sam's faq they say that any pointer style pen over about 50mW is going to be unstable without TEC or other temperature control.

so its in spec with the manufacturer and its working based on the faq which is populated by guys doing some pretty hairy DIY work with these laser systems.

so thanks for all help and input but i think i will just get the laser measured with a power meter and if i get 120mW during TEM00 i am going to assume its working fine.

keep in mind this laser was $215, not $400-500 like of the pen pointers out there so there will be some chomprimises. regardless its very bright.
 




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