Technical question

Since a laser diode is an adaptation of an L.E.D. (somewhat)

Can anyone explain why no one has produced (maybe they have and I just don't know it yet) lasers using the same crystals as colored L.E.D. indicators.

In other words, why can't a blue L.E.D. (GaN) chip be manufactured to produce coherent output??

Thanks in advance...

you're mixing orange with apples. and in some way a led is an adaptation of a bulb, so why we don't have 90W laser diodes?

Really, forget about that idea immediately xDD

Apples and oranges - Both are fruit, both grow on trees, both taste good, both make juice and both have seeds........

I cannot abandon a valid question. Especially when the answer does NOT contain any data or scientific explanation.

An LED is light emitting DIODE, a laser DIODE is also a Light emitting Diode, one is coherent, the other is not.

The technology may differ somewhat, but are very similar, an electric current is passed through a doped semi conductor, and light emerges, so where is this big difference?

both of them have different ways of functioning..in one you MUST have a population inversion, in the other u dont need and u dont have. Just read in wikipedia or Sam's laser faq...i think he (Sam) explains how lasers work quite well^^

(edit) Sam's faq: http://www.repairfaq.org/sam/laserfaq.htm (edit)

photonaholic said:

Since a laser diode is an adaptation of an L.E.D. (somewhat)

Can anyone explain why no one has produced (maybe they have and I just don't know it yet) lasers using the same crystals as colored L.E.D. indicators.

In other words, why can't a blue L.E.D. (GaN) chip be manufactured to produce coherent output??

Thanks in advance...

Click to expand...

People have created laser diodes in almost every color of LED (we don't really have yellow). But laser diodes have bee produced in IR, red, orange, green, blue, violet, and UV. A laser diode is a lot more complicated in structure, and a lot more difficult to make. Current has to be a lot higher, so you run into a lot of issues. Like mentioned, you have to have population inversion, as well as optical feedback from facets to get stimulated emission. An LED is easy, but for a laser EVERYTHING has to be perfect, everything has to go right.

So basically, we make laser diodes in blue every day, and they have been made in green as well. You mention GaN, and the GaN materials system has been used to produce lasers in UV, violet, blue, and green, and LEDs all the way up to yellow, and I believe even red. Laser diodes aren't as high in wavelength, because they're just a lot harder to make, but they are up to green now.

photonaholic said:

Apples and oranges - Both are fruit, both grow on trees, both taste good, both make juice and both have seeds........

I cannot abandon a valid question. Especially when the answer does NOT contain any data or scientific explanation.

An LED is light emitting DIODE, a laser DIODE is also a Light emitting Diode, one is coherent, the other is not.

The technology may differ somewhat, but are very similar, an electric current is passed through a doped semi conductor, and light emerges, so where is this big difference?

Click to expand...

Mode of operation: spontaneous vs. stimulated emission. Laser diodes need feedback, and therefore need a lot of different things in their structure, and that makes them a lot harder to make.

pullbangdead, when i started doin some research on lasers, and how they worked, i bumped into laser diodes. I had understood the main concept of lasers and how they worked (the simplest way: gain medium with population inversion, ~100% reflective mirror and one with some transmitance...), and i had electronics at the time (although i learned about the p-n junctions in the experimental physics lab subject) and i understood how diodes functioned (well..thats not that hard)...i think i also got how LEDs worked, not sure though cuz i dont remember too well, as i read the explanation of how the laser diodes worked a few times and i still couldnt get it, thats the part i most remember.
So now i thought "why not ask??", so can u answer my question??(of course u can, but will u take the time and answer it)
How do laser diodes work??

(just too lazy to do some research now )

Thank you pullbangdead!!

I comprehend fully the concept of lasing, Just couldn't grasp why other methods and mediums have not been used.

Glad you didn't think my question was retarded.

hey mate, I didn't meant your question was retarded! it was just a big NO xD

photonaholic said:

Apples and oranges - Both are fruit, both grow on trees, both taste good, both make juice and both have seeds........

Click to expand...

..... and was also a song from Pink Floyd (LOL)


Seriously ..... no, the materials can also be the same (almost the same, to be precise), but there are too much other things, involved, in the difference from a led and a LD .....

Just for say few of them ..... the crystal must be ultra-pure, in LD, where in leds don't count so much (a led is an emitter, a LD is basically an optical resonator built inside an emitting crystal ..... any impurity in the structure can compromise the efficency and ruin phisically the crystal) ..... not all the materials that are used for led making, can be produced in ultra-pure crystal forms ..... if this become possible, one day (someone already reached results in this field for green ), then we can have laser diodes with the same colors of the common leds at low prices ..... but til that day, no way.

Also, the leds have just conductive sides, the LD chip have conductive sides on one phisical plane, and reflective coating for form the resonant cavity on another phisical plane ..... and ofcourse, the required precision is much more high of the one needed for common leds ..... and so on.


Edit: OOPS, pullbangdead already posted a more complete reply, sorry (damn i had the thread opened too long without refresh it )

Hallucynogenyc said:

hey mate, I didn't meant your question was retarded! it was just a big NO xD

Click to expand...

No problems, none at all.

In my pursuit for an answer I found out a lot about LED manufacturing also...... Interesting stuff.

Technology is advancing at an alarming rate, so never say never.

Maybe I am old, but I have seen television evolve from a huge console to flat panel plasma in just my lifetime, AND many of the shows in the 60's were black and white.

When I was a teenager blue LED's did not exist at all, and the ones that were sold were very dim, Now I have LED bulbs in my home lighting fixtures.