Some beginner questions

[Lokepi]

Hello everyone!

This is my first thread and I hope it's in the right section.
I recently found one of my old laser pointers, and decided that I wanted to
get into making my own lasers. I have read all I could find about laser diodes, drivers and modules the last few days. (This includes the "I want to build a laser thread" that I know you're probably going to link ).
I already know a bit about electronics (or what the word is in English..) from the course I'm taking at school, such as the relations between watt, volt, amps and resistance.
Unfortunately there are still some things that are very unclear to me, that I hope you would be able to help me out with. It would be very appreciated!


Firstly, All the sites that sells laser diodes states the output watt, not the ampere. How am I supposed to know what resistance and voltage is needed for a LM317 driver if I don't have the ampere and voltage required by the diode?
also, if a red laser diode requires a voltage of 3V, and have a output of 250mA, does that mean it have a output of 750mW? It doesn't seem right..
(I found a very helpful guide about calculating the required power supply voltage and the resistance needed here: "link", but the whole driver part is still a little blurry)

Secondly, Is there anything else than the resistance that changes depending on the driver? For example, if a driver from a old 1$ laser pointer have the right resistance (10 ohms for a red 650nm 250mA laser for example) would I be able to use that for any laser diode that requires that certain resistance?

Thirdly, could anyone recommend a site that sells good safety glasses for these kind of things? Wouldn't want to loose any eyesight

PS: English isn't my first language, so please excuse any mistakes.
Thanks for any help!

 

[marianin]

hi men i only have the answer to the first and the third think.

first a 445nm laser diode needs around .8 to 1.25 ampers to have a very nice duty cicle and life span,

the laser diodes are very inefficent that means that a red laser diode with 3v and 250mw gives you around 150mw that means around 600mw are converted to heat.

third i think these laser googles are good http://laserpointerforums.com/f44/cheap-safety-glasses-tested-71621.html

 

[marianin]

hi men i only have the answer to the first and the third things.

first a 445nm laser diode needs around .8 to 1.25 ampers to have a very nice duty cicle and life span,

the laser diodes are very inefficent that means that a red laser diode with 3v and 250mw gives you around 150mw that means around 600mw are converted to heat.

third i think these laser googles are good http://laserpointerforums.com/f44/cheap-safety-glasses-tested-71621.html

 

[sinner]

The Optical Power Output [Po] of a laser diode is a measure of its emission of coherent light.. It is measured in milliWatts and Watts too.

 

[Lokepi]

@Marianin; Thanks for the link to the safety goggles. . Other than that your answer didn't really tell me anything that I didn't already know, but thanks anyway! Also, shouldn't the required ampere depend on more than the wavelength? Laser diodes with a higher output should require more ampere, right?

@sinner: So does that mean you can not calculate the output watt using the output Ampere and required voltage?

Still need some help with this though. Does the laser diodes tell you what ampere and volt they need? (Like on some label when you buy them)? Because I have only found the Output watt on sites that sell them.

 

[sinner]

Measuring devices for optical output incorporate a sensor which will measure the intensity of light in milliWatts.
You can calculate the electrical power in theory but not optical power, That is because the optical power vary diode to diode , it can be roughly estimated if you have a graph which will only provide the data curve for that particular diode type which was tested and the readings were plotted in the graph for reference.
You might want to read some info about laser measurements in laser measurements section
PHR-803/PHR-805 = 125mA @~6V - 100mW
405nm 6x GGW-H20L= 180-190mA @~6V 150-180mW
16x Red Laser Diode from DVD-Burner = 250-300mA @3V 200mW
LPC-815 = 420mA @3V ~275mW
LPC-826 = 500mA @3V ~325mW
445nm LD = 1.8A ~4.6V ~1.5-2.0W
445nm LD H1600 = ~2.3A @4.6V 2.0-2.7W

These are some of the absolute maximum ratings of some 5.6mm laser diodes that i know of, You can also ask here at lpf or use the Search button first.

Hope this helps.
:beer:

 

[Lokepi]

Measuring devices for optical output incorporate a sensor which will measure the intensity of light in milliWatts.
You can calculate the electrical power in theory but not optical power, That is because the optical power vary diode to diode , it can be roughly estimated if you have a graph which will only provide the data curve for that particular diode type which was tested and the readings were plotted in the graph for reference.
You might want to read some info about laser measurements in laser measurements section
PHR-803/PHR-805 = 125mA @~6V - 100mW
405nm 6x GGW-H20L= 180-190mA @~6V 150-180mW
16x Red Laser Diode from DVD-Burner = 250-300mA @3V 200mW
LPC-815 = 420mA @3V ~275mW
LPC-826 = 500mA @3V ~325mW
445nm LD = 1.8A ~4.6V ~1.5-2.0W
445nm LD H1600 = ~2.3A @4.6V 2.0-2.7W

These are some of the absolute maximum ratings of some 5.6mm laser diodes that i know of, You can also ask here at lpf or use the Search button first.

Hope this helps.
:beer:

That's a great explanation, Thanks! It really clarified a lot! :yh:

 

[marianin]

@Marianin; Thanks for the link to the safety goggles. .

i use this glasses and there are very good try it

 

[Lokepi]

Hey again, I have a new question, and instead of making a new thread, I'm just gonna ask it here instead:

I looked on the net for a 650nm 250mW diode, but the best thing I could find was this 660nm (Everything else was only shipping to the USA):"link". It says that the operating current should be <340 mA. Now the question is; How much output power would I get if I gave it 250mA @ 3V using a LM317 based driver?

 

[marianin]

Hey again, I have a new question, and instead of making a new thread, I'm just gonna ask it here instead:

I looked on the net for a 650nm 250mW diode, but the best thing I could find was this 660nm (Everything else was only shipping to the USA):"link". It says that the operating current should be <340 mA. Now the question is; How much output power would I get if I gave it 250mA @ 3V using a LM317 based driver?

it says that the operating current is 340ma and the average power is around 150mw

i recommend you that put the 340ma for a desent power but if you want to put the 250ma you will be get around 100mw

 

[lman]

Hey again, I have a new question, and instead of making a new thread, I'm just gonna ask it here instead:

I looked on the net for a 650nm 250mW diode, but the best thing I could find was this 660nm (Everything else was only shipping to the USA):"link". It says that the operating current should be <340 mA. Now the question is; How much output power would I get if I gave it 250mA @ 3V using a LM317 based driver?

Lm317 drivers will need about 6v to function.

 

[Lokepi]

@marianin Are you sure? the site says that the Slope Efficiency is 0.97 mw/ma. I thought this meant I got 250*0.97 mW if I out in 250 mA. And 340mA where only required for pulsing the laser at a output of 340 mW.

@Iman Well, I know that. I meant that the diode itself requires 3v.

If anyone could recommend a better 650nm 200+mW diode in the Eu it would be great too .

 

[marianin]

@marianin Are you sure? the site says that the Slope Efficiency is 0.97 mw/ma. I thought this meant I got 250*0.97 mW if I out in 250 mA. And 340mA where only required for pulsing the laser at a output of 340 mW.

@Iman Well, I know that. I meant that the diode itself requires 3v.

If anyone could recommend a better 650nm 200+mW diode in the Eu it would be great too .

man it says 340ma = 200MW (max)

that means with 250ma you will get 150mw(MAXXX)

 

[Lokepi]

man it says 340ma = 200MW (max)

that means with 250ma you will get 150mw(MAXXX)

I'm sorry, but nowhere it says that (if it does, please point out where). 200mW isn't max for pulse. And where do you get the 150mW from? is it just a guess?. Also, weren't you doing your first build right now? I would rather get some information from someone that have some more experience. (No offense)

 

[marianin]

I'm sorry, but nowhere it says that (if it does, please point out where). 200mW isn't max for pulse. And where do you get the 150mW from? is it just a guess?. Also, weren't you doing your first build right now? I would rather get some information from someone that have some more experience. (No offense)

ok :cryyy:

 

[Ghostchrome]

^^ It looks like the seller isn't even sure what diode that is. They are taking a guess from the "closest specsheet they can find", the ML101U29 (LPC diode). So that's all we've got to go off.

It's tough to tell how much power you are going to get from feeding any diode any given amount of current. Each diode varies a bit, so it's not an exact science.

If it is an LPC-826 like the seller suspects, you can give it 450-500mA no problem and it should be about 250-300mW. The only way to tell for sure is buying one and trying it out.

Welcome to the laser hobby. :beer: