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confused by laser watt and maxium current

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ramin110

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i bought 1.6 w 450nm blue laser diode (osram) from ebay and I now confused by maximum current my laser can handle. in the datasheet it says you can put 1.5 Amp maximum current with typical 4.8 volt for maximum operate but my blue laser is 1.6 watt. if the formula for watt is p = v*i so my laser must be 4.8*1.5 = 7.68 watt laser or the term watt and power is different from above formula?:thinking:

link of datasheet:
http://www.osram-os.com/Graphics/XPic1/00088311_0.pdf

sorry for bad English.
thanks.
 
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Hi rain,
Driver set to 1.8A max for this diode 1.7A for safety but 1.8A will be fine and powered by 2-lithium ion cells . this diode will handle it with really good heat sinking. If you don't have a host to put it in check out the buy,sell and trade section and look for my sales thread for Plug n Play set ups. solder two wires to your diode ,driver set and your lens done ..frome the diode you have you will be getting about 1800mW's give or take from a 1.8A driver and a G2 lens. With a 3 element lens it drops down about 300mW but you get a much more rounded beam ..

Rich:)
 
P=V*I is input power, driver takes care of that.

We are more interested in optical power, i.e. intensity of the beam and number of photons.
It is measured with LPM.

optical power / V*I = efficiency

V*I - optical power = waste heat
 
Re: confused by laser watt and maxmium current

so if I set current to 1.8 amp with proper heat sink my laser will not blow up?:can:

Thanks everyone for your response.
 
Re: confused by laser watt and maxmium current

hi,
It will be fine these diodes that you have will handle 1.8A or lower .

Rich:)
 
Blue is beautiful and will burn like the dickens at that power output level and sting like a bee if you put your hand in front of it too long, not recommended. One thing to be aware of though, if completely new to this hobby, 450nm blue is only 10% as bright to the human eye (like what, would I be looking with a dogs eye?) compared to green, so milliwatt (or watt) to milliwatt, green is about ten times brighter for the same power output level. Not that you can see "oh, that's ten times brighter", but I thought I'd mention that blue although powerful just won't look as bright as green for the same power output level. i.e, a 200mw green 520-532nm laser beam will be just about as bright as a 2 watt 450nm blue laser beam. We could split hairs on this some, but this gives a general idea of the difference between blue and green lasers, in regard to perceived brightness.
 
ramin110 said:
i bought 1.6 w 450nm blue laser diode (osram) from ebay and I now confused by maximum current my laser can handle. in the datasheet it says you can put 1.5 Amp maximum current with typical 4.8 volt for maximum operate but my blue laser is 1.6 watt. if the formula for watt is p = v*i so my laser must be 4.8*1.5 = 7.68 watt laser or the term watt and power is different from above formula?:thinking:

link of datasheet:
http://www.osram-os.com/Graphics/XPic1/00088311_0.pdf

sorry for bad English.
thanks.
Click to expand...

There is loss, the laser diodes are not 100% efficient,

If you drive your diode at 1.5 amps and 4.8 volts you are putting 7.2 watts into the diode and getting out 1.6 watts of light energy and 5.6 watts of heat energy, the heat energy is dissipated through the diodes body and into the surrounding heat sink that you will need to have it mount in.

The laser diode is rated in real light energy output where as a household lightbulb is rated at the input watts, the truth is a 100 watt incandescent household light takes 100 watts input and puts out something like 4 watts of light energy and 96 watts of heat energy.
 
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I wish I could find data on the case temperature of these diodes mounted in various sized heat sinks to see what the temperature differential is between the diode and the heat sink it is mounted into. Something I will do in the future if I don't find where someone else has already done so.
 
I have seen in DTR's testing videos where he backs down the current and the output numbers tick up, but at higher drive current the output number ticks slowly down.

It's as if the diode it's self is a heat bottleneck when driven too far above spec, we could wrap the laser diode in diamond and still the junction heat can't escape the backing plate as fast as it's made at higher current.

What kills me is the 5.6 and 9mm housings have a seemingly ferrous backing plate, it sticks well to a magnet, I am guessing it's ferrous.

Maybe a TEC or refrigerated heat sink approach could allow some much higher outputs and without fading, to a point anyway, I know a chilled diode will output higher than normal until it warms up.
 
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I posted this before, but I can't find it. This is a simple layout of a laser and a simple explanation...

Power source--driver--diode--filters/lenses--beam

Everything to the left of the diode is ELECTRICAL POWER.
Everything including, and to the right of, the diode is OPTICAL POWER.

There are formulas to predict what both will be, but they are not interchangeable.
 
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