Running Blu Ray at 900ma 3.6 watts input ?

[drjava]

I bought a Blu Ray 445nm diode in a module from DTR here on the forum.
I put it in a large finned heat sink and I connected it to a controlled current controlled voltage lab power supply. I replaced the lens with a glass one.
Once I got it to lase at low power I focused it.

Then I put a black balloon in the beam. Nothing happened. I continued to slowly increase the amperage. I got up to 900-1000mA

Now I have a solid powerful blue beam that instantly pops black balloons in a microsecond. But when I read about these diodes, I see you're not supposed to exceed 500ma. It's at around 4 volts. So my power supply is putting out about 900ma at about 4 volts so it's just under 4 watts? Am I actually running this diode at 3.6 watts? It didn't seem to pop anything below this amperage. I haven't run it for more than 30 seconds at a time. Is it OK to run it at this amperage for short periods in a heat sink?

Why isn't it popping balloons at much less than 900ma? At 4 volts it would seem 250ma would be a watt and why wouldn't that work on balloons?

It seems the milliamps I need are quite excessive compared to what I read about.

Anyone can explain this? Thanks

 

[chipdouglas]

2 things... first, a blu-ray is not a 445nm. it is 405 which makes it violet in color.

2nd, 445nm lasers have horrible beams, how far way are you trying to pop this ballon? the focal point is with in a foot. after that you need a lot of power to pop at a distance.

michael.

 

[Helios]

3rd just because 4V at 1000mA = 4 Watts dosent mean you get 4 Watts out in blue light. At 1000mA you should be around 1W out which is still a lot of photons but as chipdouglas explained the 445nm are multimode and thus have huge elliptical beams (for a laser at least). Up close they burn like mad but at any sort of a distance there power density really drops off.

 

[lasersbee]

I guess it's time to put the reading glasses on....

I hope you are using appropriate Laser Safety Goggles/Glasses
when plying with your Dangerous High Output Laser...


Jerry

 

[drjava]

thanks
1 It is 445 so I guess that puts me in the wrong forum
2 I do wear goggles
3 If 4 watts in means about 1 watt out does that mean it's about 25% efficient as a rule?
4 How many amps can I run input to it for up to 30 seconds at a time?
5 I'm going to make alternate portable power based on my RC airplane LiPo 11.1 battery that can put out more than 30 amps. Obviously I'll run it through a driver to limit the current. So this will make it portable and I can try it out at longer distances.
This is where I'd need to know the max safe input current for 15 to 30 second bursts.
thanks again.

 

[lasersbee]

You need to be checking the actual current going to the Laser
Diode... not the current used by your Driver... Drivers are
rarely 100% efficient...

The wattage as Electrical Power used and the wattage as
Photonic Power output are not related in a ratio of 1:1..
They are 2 different animals....


Jerry

 

[drjava]

Of course not 1 to 1, but characteristically 4 to 1 ? There has to be a characteristic efficiency that's known.
Thanks.

 

[lasersbee]

If you want to measure it your way.... yeah... I guess...

You can't directly measure the current your LD and LD Driver
draw from the batteries with a Laser Power Meter...
And you can't directly measure your Laser Diode Beam power
with an Amp Meter....


Jerry

 

[rhd]

Of course not 1 to 1, but characteristically 4 to 1 ? There has to be a characteristic efficiency that's known.
Thanks.

There doesn't HAVE to be anything. Material tolerances and quality control are not a mission critical concern when you're talking about laser diodes that are essentially used 24 at a time, as substitutes for a light bulb.

There is LIKELY to be some consistency to the ratio between the power you put in, and the optical power you get out, across multiple similar diodes. However, there's no constant. That's why we all like to own LPMs - because an input current of 1.5A can just as easily result in an optical output of 1.3W as 1.7W.

The only thing you can be certain of, is that when you put 4W of power into a 445nm diode. You will DEFINITELY get 4W of power out of it.

Figuring out how much you'll get out as heat vs light, is another story