most users online...

[BoomDog]

IR within a beam can manipulate a lasercheck reading. If the meter is set to, say 532nm, and a pure green 1 watt laser is shot into it, and then a visually dimmer and less powerful green w/ enough IR, the meter will output relatively the same power. Obviously if a spectrometer is used, you can tell the difference, but my worry is that I will not be getting 1 watt of green. Most 1 watt green lasers w/ IR filters actually would supposedly emit >1.5 watts to a normal power reader without the filter, but the difference is excess IR and is not visible.

Not to mention, IR is more dangerous to not only your eyes, but your skin as well, as it is absorbed by many more materials than any visual color. In essence, IR is sometimes referred to as heat energy, just because of it's excellent ability to be absorbed and converted to heat. That means it can fry your eyes that much quicker. Plus, I plan to use this in public events, and I believe in the US it is required to have an IR filter on a laser meant for such things.

[cruch]

thats really bad!

Thanks for the update!

[nono shen]

I am here , about the laser with IR filter , I must say something . laser with IR filter is necessary,every laser must add filter , without filter will be dangerous , no matter the worker or the customer . if it is without filter isnot the eligibility. the problem is depend on the quality of the filter , the better filter will get the less out put . lasers no matte which in any company , will out put some IR light , CNI and other company is the same .

[BoomDog]

Yep this is very true; there is never such thing as a perfect optical device, and IR filters certainly fall into this category. Nono-shen, good to see ya again; sent ya another PM responding to your last message. :P

Oh, BTW cruch, sorry I totally hijacked your thread ops:

[BoomDog]

Alright, looks like I found my laser; I'm wiring the money over this week, after nono-shen mentioned an additional IR filter will be installed. Rather be safe than sorry, particularly if I'm using this in public. She was gracious enough to quote me the price of a normal filter, so THANK YOU! Can't wait! :P

She also confirmed that she would be sending the class IV sticker, in case anyone was wondering, though that was already figured out here obviously. Plus my DT-40's, AlphaliteXC Pro software/interface, and pre-varianced projector casing is all shipping out at some point this week. I'm going to have waaay too much fun next week!

[cruch]

early crismas gift!!! hehe
I will also order an 1 Watt green laser from nono. Since it has IR filter.

Then...is it
1 Watt with IR filter
or
1 Watt without then adds IR filter? will it be less power then?

[cruch]

I have read that laser with IR filter is 10-20% higher power than without. True?
so a 1watt is only 800mw with IR filter? and 1watt witout...

[BoomDog]

Sounds reasonable, I'm not very sure though. Normally, manufactures measure the power with an IR filter installed (or at least the honest manufactures do). So a 1 watt green with is probably 1.2 to 1.3 without; though I have heard of larger leaks than that.

[buffo]

Glad to see that Nono Shen agrees with us that IR filters should always be installed on DPSS lasers. Her post (above) is right on the money, and is essentially the same thing we've all been saying: Lasers without IR filters are dangerous.

Cruch: To answer your earlier question, if a DPSS laser does NOT have an IR filter, then the laser output will register higher on a power meter. This is because the leaking IR will cause the sensor to respond just as the visible beam does. (Actually, the sensor response is not linear with changing wavelengths. At some IR wavelengths the sensor might be twice as sensitive as it is to green light.)

If you buy a 1 watt laser, that should be 1 watt at whatever wavelength the laser is rated for. (532 nm, 473 nm, etc.) If there is IR present in the beam, then you have a problem and need to install an IR filter. But in no case should the leaking IR be included in the 1 watt. To do otherwise is dishonest. Yet, some manufacturers do include the leaking IR power in with the total output power figure for their lasers. It would be wise to avoid such unscrupulous vendors.

As for how much IR could be leaking in a laser that lacks an IR filter - that's more difficult to predict. A 1 watt laser will normally have between 5 and 7 watts of pump energy at 808 nm. Depending on the quality of the optical coatings inside the lasing cavity and the efficiency of the vandiate crystal itself, you might expect to see 500 mw to 1 watt of that pump IR leaking through. Then there's the 1064 nm IR that manages to leak past the frequency doubling stage. You usually will have almost double the 1064 nm power as you end up with in 532 nm output. So, once again depending on the quality of the optical coatings and the efficiency of the KTP crystal, you might see another 250nm to 500 mw of 1064 nm IR. (Remember that the efficiency of the frequency doubling process can be greater than 50%, whereas the conversion of 808 nm pump to 1064 nm IR is generally around 30%.)

However, if you have a 1 watt DPSS laser and you remove the IR filter, you may well only see an increase of a few hundred milliwats of power due to leaking IR, *IF* the laser has exceptional optical coatings. (Because good optical coatings inside the lasing cavity mean that more IR stays inside the laser, where it's working to make more light, rather than leaking out and being lost.) But on less-expensive models, you might see the power reading *double* when you remove the IR filter. That's because at some point it's cheaper to make the pump diode larger than it is to install better optics to reduce IR leakage.

But in any case, the final IR filter is always a must. The output beam shouldn't have more than a few mw of IR.

Adam

[cruch]

Thanks for the info! I do understand now.
We should set sticky tread on IR filter or something. For all other newbies...just like me...