# Power Equivolents between laser colors?

#### Ashton

##### Enlightened
I've been reading and the way I understand it, you get the same power from a lower wattage green laser as from a higher red, and an even lower blue (lol, like I could ever afford a blue)

What's the rough equivolent on power with these? Is it as little as 100mw green ~ 110mb red, or is it closer to 100mw green ~ 175mw red? And how do the new blue lasers fit in?

#### liveforphysics

##### Enlightened
The power of the lasers is all exactly equal between lasers of same XmW.

Your eyes/brain perceives 555nm to be brightest, and has an exponential drop in each direction towards longer and shorter wavelegnths. Looks similar to a bellcurve.

You need to find the light color human perception chart to answer your question, and even then, its going to vary a bit between indivdual people.

But as far as power levels, a 5mW UV = 5mW blue = 5mW green = 5mW red = 5mW IR. The shorter wavelegnths require less photons to make that same 5mW, because each photon carries more energy with it, but we measure lasers with energy and not PPFD, so its basically a mute point for our applications.

#### Ashton

##### Enlightened
ok, I thought that, to use a common application, you required a red laser of X mw to light a match in 5 seconds from 3 feet away, but you could use a green laser of <x to light that same match in 5 seconds from 3 feet away.

If they all produce the same powered beam, why they the \$\$\$ difference between the r/b/g lasers with high powered red laser being cheeper than a green of only around 1/2 the power?

#### liveforphysics

##### Enlightened
A high power red requires a single quantium-well junction and a lens.

A green requires a quantium-well junction going through a lens into a crystal into another crystal into another lens (optional IR filter anywhere at this point) into a focusing lens.

A blue can be done with a similar setup as the green, or with a single nichia diode junction that happens to require a pretty elaborate process to make, and still has huge demand vs supply.

In a few years, very high power blues will be cheap common items. Blue and red lasers will both be dollar store items soon, and greens will still be \$\$. This is because the market has no reason to develop a single diode that can efficiently emmit green because they can do 405nm which is superior for optical data storage. If somebody stumbles upon a junction to do green in a single step, it likely wouldn't even be built because the market share for green lasers is not worth taking. Optical storage is why red lasers are now pennys, and optical storage is why companys bother investing time in solidstate laser design. Green has no roll in optical storage these days.

#### 2xTrinity

##### Flashlight Enthusiast
ok, I thought that, to use a common application, you required a red laser of X mw to light a match in 5 seconds from 3 feet away, but you could use a green laser of <x to light that same match in 5 seconds from 3 feet away.
False. In terms of lighting matches, or heating things up, all that matters is how many mW you have. The only difference is that green will appear brighter than any other color at the same power. A X mW IR laser would set things on fire just as much as a red or green, and wouldn't be visible at all.

If they all produce the same powered beam, why they the \$\$\$ difference between the r/b/g lasers with high powered red laser being cheeper than a green of only around 1/2 the power?
The green is more expensive as it isn't just a single-component laser diode. They use an IR diode and a set of crystals to convert the wavelength from around ~1060 to 530.

liveforphysics said:
A high power red requires a single quantium-well junction and a lens.

A green requires a quantium-well junction going through a lens into a crystal into another crystal into another lens (optional IR filter anywhere at this point) into a focusing lens.

A blue can be done with a similar setup as the green, or with a single nichia diode junction that happens to require a pretty elaborate process to make, and still has huge demand vs supply.

In a few years, very high power blues will be cheap common items. Blue and red lasers will both be dollar store items soon, and greens will still be \$\$. This is because the market has no reason to develop a single diode that can efficiently emmit green because they can do 405nm which is superior for optical data storage. If somebody stumbles upon a junction to do green in a single step, it likely wouldn't even be built because the market share for green lasers is not worth taking. Optical storage is why red lasers are now pennys, and optical storage is why companys bother investing time in solidstate laser design. Green has no roll in optical storage these days.
Interesting. This is unfortunate as green, if they could make a single-stage diode, would be the most efficient in terms of visible brightness for input power as green gives you the most lumens per watt (output). I'd love to have a tiny keychain style ~2mW green laser for actual pointing.

In terms of optical storage, if they could get a shortwave UV diode work on a disc, I'm sure they woudl do that even though it's completely invisible -- there it's all about using the shortest wavelength possible.

#### liveforphysics

##### Enlightened
The cutting edge blue-ray disk burners are useing 395nm and 405nm lasers... UV is here allready for optical storage, and the next jump in storage density is slated to be a 220nm UV laser... Some people think that IR lasers are dangerous just because they are invisible, imagine when people are playing with 220nm lasers... It will burn you while changeing DNA in local cells to cause cancer...

#### comozo

##### Enlightened
2xTrinity said:
False. In terms of lighting matches, or heating things up, all that matters is how many mW you have. The only difference is that green will appear brighter than any other color at the same power. A X mW IR laser would set things on fire just as much as a red or green, and wouldn't be visible at all.

The green is more expensive as it isn't just a single-component laser diode. They use an IR diode and a set of crystals to convert the wavelength from around ~1060 to 530.

Interesting. This is unfortunate as green, if they could make a single-stage diode, would be the most efficient in terms of visible brightness for input power as green gives you the most lumens per watt (output). I'd love to have a tiny keychain style ~2mW green laser for actual pointing.

In terms of optical storage, if they could get a shortwave UV diode work on a disc, I'm sure they woudl do that even though it's completely invisible -- there it's all about using the shortest wavelength possible.

Nada the brightness is only apparent not actual. Human vision is most sensitive to that wavelength specifically 555.5 nm. I do believe that that conversion rate of green dpss lasers is not as high as directly injected dpss lasers.

#### Canuke

##### Enlightened
liveforphysics said:
The cutting edge blue-ray disk burners are useing 395nm and 405nm lasers... UV is here allready for optical storage, and the next jump in storage density is slated to be a 220nm UV laser... Some people think that IR lasers are dangerous just because they are invisible, imagine when people are playing with 220nm lasers... It will burn you while changeing DNA in local cells to cause cancer...

Some researches in Wisconsin demonstrated this last year when they used a 266nm UV laser to, er, cut some cheese.

IMO, the danger factor with 405nm lasers is much higher than with equivalent red or green, because the photochemical threshold where photons can damage organic molecules starts just below 500nm. (I can't for the life of me remember where I read that, and can't find a citation... what I did find is that the point where photochemical reactions become dominant over thermal effects is mediumwave UV, about 250nm).

#### dudeldam

##### Newly Enlightened
The energy of ONE photon is E=hf with h=6.63*10^(-34)Js and f=c/lambda with c=speed of light and lambda = wavelength.

You get E=h*c/lambda. On the lambda there is no square or root or other funny or difficult mathematical symbol, so the energy E goes by 1/lambda.

If you define one certain energy as "standard", for example your laser at 600nm, and half the wavelength without changing anything else, the photons will have double E at 300 nm and 3times E at 200 nm.

Of course, simple physics can´t predict how many photons your laser will emit and how efficient it will change electricity to light. The formula just applies for single light quants.