Is it possible to achieve the same power density using an LED as with a laser diode?

[ArKi]

Hi everyone!

I'm currently working on a project where I would like to focus a light source into a line. We are trying to achieve the highest power power density, and I was just wondering if it would be possible to use an LED, SLD, or some other light source to achieve the same power density as one could with say, a 1W laser diode?

Assume you can using any number of focusing optics to achieve this power density. Also, it would be good to know if you use what power/brightness for an LED is equivalent to say, a 1W laser diode if you can use any focusing optics?

 

[CurtisOliver]

You would need to have a very powerful light source passing through a cylindrical lens. Lasers focus more tightly due to there coherence, and thus would have a higher beam intensity. A ordinary light source would not focus in as tightly and would not all focus at the same rate either. This leads to lower density and larger line.
It is difficult to pinpoint exactly how much power you would need to achieve the same. May I ask, why are you not just using a laser?

 

[ArKi]

We are using a laser currently! Just wanted to compare the options using an LED because it might be a cheaper option from a dollar perspective. Do you know if they make LEDs powerful enough to focus down into a laser line?

 

[CurtisOliver]

You would need to invest in super bright LED's and then pay for heat sinking methods before you get anything close to that of a laser. I'd say you need around 10-20W. Just a warning though. I brought myself a 10W UV led for a project of mine. I forgot about cooling and the LED heated up to around 100 degrees, softening the acrylic box around it. I had to get radial finned heatsinks and a computer fan just to keep it cool. The other issue is that they don't use a single emitter. They are arranged into a grid 3x3 etc. This further limits your focusing capabilities. What are you using your laser/led line for?

 

[diachi]

You're not going to be able to achieve the same power density with an LED - you'd need a very powerful LED (Much of the power will be lost from improving the output) and lots of expensive optics to make it work at all and even then, it's not going to come close to the laser diodes we have now.

 

[CurtisOliver]

Best stick with the best form of light there is ... Lasers

 

[Cyparagon]

Why do you need a laser line? For what will you be using it? Why is power density so crucial?

Why does it seem I'm the only one that thinks application is relevant? I would like to see more people bring this up. The reason is the problem is usually unrelated to lasers, and we waste a bunch of time on a solution that wasn't viable from the start.

 

[Pickles]

Why do you need a laser line? For what will you be using it? Why is power density so crucial?

Why does it seem I'm the only one that thinks application is relevant? I would like to see more people bring this up. The reason is the problem is usually unrelated to lasers, and we waste a bunch of time on a solution that wasn't viable from the start.

I'm with Cyparagon. Please share some more details as it will help the entire community here. Cheers!

 

[bdgreenb]

This is one of those rare situations where our answer is that a laser is best for this application. Never don't use a laser when you should

We usually get questions like, "Can i light a cigarette with a laser?"
The answer is yes, but a lighter would work better and be safer.

 

[Cyparagon]

This is one of those rare situations where our answer is that a laser is best for this application.

How can you say that when YOU DON'T EVEN KNOW WHAT THE APPLICATION IS?

 

[diachi]

How can you say that when YOU DON'T EVEN KNOW WHAT THE APPLICATION IS?

I'm currently working on a project where I would like to focus a light source into a line. We are trying to achieve the highest power power density, and I was just wondering if it would be possible to use an LED, SLD, or some other light source to achieve the same power density as one could with say, a 1W laser diode?

We are using a laser currently! Just wanted to compare the options using an LED because it might be a cheaper option from a dollar perspective. Do you know if they make LEDs powerful enough to focus down into a laser line?

That seems like enough information to supply an answer to me - although it would be nice to know more about the application, that doesn't mean we can't answer the question with the information provided.

 

[Cyparagon]

If I may cite one of my favorite bash quotes:

<glyph> For example - if you came in here asking "how do I use a jackhammer" we might ask "why do you need to use a jackhammer"
<glyph> If the answer to the latter question is "to knock my grandmother's head off to let out the evil spirits that gave her cancer", then maybe the problem is actually unrelated to jackhammers

 

[diachi]

If I may cite one of my favorite bash quotes:

Point taken :crackup::crackup:Now I need to go read some bash quotes...

We can provide an answer to the question: [Can I]" achieve the same power density as one could with say, a 1W laser diode?".

But if we know the application then yes, we may be able to provide further assistance to OP outside of the initial question.



AS I said ... interested to know the application myself either way.

 

[bdgreenb]

How can you say that when YOU DON'T EVEN KNOW WHAT THE APPLICATION IS?

Fair enough. I used "application" incorrectly.:can:

From the post i figured he was trying to achieve power density in a line. I thought a laser would be his best option compared to other light sources available.

 

[ArKi]

Hi guys, thanks for all the replies! So the application is fluorescence microscopy. Basically we are scanning a laser line over a sample, and our exposure time will be on the order of 0.5-1ms per image of the line. We also don't foresee there being any other major sources of light loss in regards to the optics.

Right now, we've tested with a 1W 405 nm laser, which works well. However, as we expand the system, traditionally in fluorescence micrscopy, systems use the following wavelengths: 405 nm, 488 nm, 532 nm, 561 nm, and 638 nm. 405 and 638 nm diodes are easy, but finding a good solution at the other lines (or close to it) has been difficult, and most of the options I've found are DPSS ones that are thousands of dollars per laser. I think we're flexible on the exact wavelength, but we do need a few options between 470-560 nm.

Just trying to find the most cost-effective option, that's all!

P.S. It's also hard to say from our end if 1W is overkill, and if we can get away with something like 200-300mW. I would also be interested in ideas for that power range. Just to give you a sense of the size of the line, using a 4x microscope objective we are talking about 2mm x 4 um.

 

[diachi]

Hi guys, thanks for all the replies! So the application is fluorescence microscopy. Basically we are scanning a laser line over a sample, and our exposure time will be on the order of 0.5-1ms per image of the line. We also don't foresee there being any other major sources of light loss in regards to the optics.

Right now, we've tested with a 1W 405 nm laser, which works well. However, as we expand the system, traditionally in fluorescence micrscopy, systems use the following wavelengths: 405 nm, 488 nm, 532 nm, 561 nm, and 638 nm. 405 and 638 nm diodes are easy, but finding a good solution at the other lines (or close to it) has been difficult, and most of the options I've found are DPSS ones that are thousands of dollars per laser. I think we're flexible on the exact wavelength, but we do need a few options between 470-560 nm.

Just trying to find the most cost-effective option, that's all!

P.S. It's also hard to say from our end if 1W is overkill, and if we can get away with something like 200-300mW. I would also be interested in ideas for that power range. Just to give you a sense of the size of the line, using a 4x microscope objective we are talking about 2mm x 4 um.

This is all from some quick reading... Feel free to correct me if I'm wrong.

As far as I know, you're best with lasers if you want the best resolution - although the cost can certainly be prohibitive. From what I've read, resolution wise, your best with lasers, then mercury/xenon arc lamps then LEDs - the larger emitter size of LEDs poses a problem when it comes to microscopy - although it is possible to use them as a light source, actually making that light source useful is much more complicated than with lasers and the results aren't generally as good.

Arc lamps are often a better than LEDs due to a small "emitter/source" size as well as a high luminous flux - arc lamps are the "original" light source for fluorescence microscopy it seems.

The cheapest option you will find for the missing wavelengths you have listed, or at least something close, is a used multi-line Argon-ion laser (Or better yet, Ar/Kr ion, that way you'll get the red lines covered and maybe the yellow too.). It'd certainly be cheaper than buying a new OPS 488nm source or 561nm DPSS source. 532nm is relatively cheap though. Gas ion lasers are however, very inefficient, often very fragile and somewhat harder to come by as they get replaced by newer technology.

.


So can you use LEDs for fluorescence microscopy? Yes - certainly. Can you achieve the same power density as a laser?No, at least not in any meaningfully small "beam size".

Also ... 1W of 405nm? That seems like it'd be entirely too much power - wouldn't that cook your sample?