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Flying saucer; quantum dots hold secret to brighter, better lasers

Benm

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I think the gap will close regardless, at least if the past is any preface to the future.

About 10 years ago it was much wider, you basically had the IR and red diodes up to about 650 nm, with the occasional low powered 635-ish diode available. On the other end 405 nm was pretty much the limit.

445 nm blue was an obvious success and has commercial application today, and the gap shrunk from the blue end down to green by now with 520 nm being readily available.

From the red side there seems to be little improvement, even now the limit is about 638 nm at reasonable cost.

It may be required to use a different semiconductor material to make lasers in between, getting something to lase with a bandgap of 600 or 550 nm seems to be very difficult. This is a very small difference in bandgap voltage, but it covers the visual spectrum from orange to yellow - i guess an unlucky coincidence, as we can make laser diodes over a very wide spectrum range in the near IR.
 



steve001

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I think the gap will close regardless, at least if the past is any preface to the future.

About 10 years ago it was much wider, you basically had the IR and red diodes up to about 650 nm, with the occasional low powered 635-ish diode available. On the other end 405 nm was pretty much the limit.

445 nm blue was an obvious success and has commercial application today, and the gap shrunk from the blue end down to green by now with 520 nm being readily available.

From the red side there seems to be little improvement, even now the limit is about 638 nm at reasonable cost.

It may be required to use a different semiconductor material to make lasers in between, getting something to lase with a bandgap of 600 or 550 nm seems to be very difficult. This is a very small difference in bandgap voltage, but it covers the visual spectrum from orange to yellow - i guess an unlucky coincidence, as we can make laser diodes over a very wide spectrum range in the near IR.

Back in the late 90's I bought a laser pointer that lased at @ 633nm. It cost $450.
 

Benm

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Was that a diode laser or some kind of 'portable' HeNe?

633 is spot on for HeNe, but quite rare for diode lasers unless it was cherry picked from a batch.
 

steve001

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Was that a diode laser or some kind of 'portable' HeNe?

633 is spot on for HeNe, but quite rare for diode lasers unless it was cherry picked from a batch.
It was a diode laser. I got it from a company, one of the first to sell laser pointers, known as DeHarrport Trading company. While looking to see if they were still in business I came across this old thread. http://laserpointerforums.com/f44/h...en-lasers-when-they-first-came-out-95603.html
Look at the prices.
 

CurtisOliver

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It may be required to use a different semiconductor material to make lasers in between, getting something to lase with a bandgap of 600 or 550 nm seems to be very difficult. This is a very small difference in bandgap voltage, but it covers the visual spectrum from orange to yellow - i guess an unlucky coincidence, as we can make laser diodes over a very wide spectrum range in the near IR.
It may be possible that in a few years, we will see 620nm diodes using AlGaInP, but <610 may be a bit far fetched. I believe a new semiconductor is in order for the gap to be filled. Possible a mix between GaN and AlGaInP is what is could be needed.

AlGaInP has achieved 626nm, but the bandgap to watch is with InGaP/InAlGaP. We have demonstrated a technique called quantum well intermixing (QWI) and have shown that 608nm can be achieved at room temperature. Using this method along with temperature tuning, 565nm is lowest achieved wavelength tested. I wonder how much longer it will be until we have room temperature 580nm diodes? :whistle:

626nm: Link won't work so search for 'Monolithic 626 nm single-mode AlGaInP DBR diode laser'
608nm: IEEE Xplore Full-Text PDF:
 
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Benm

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That would mostly depend on how hard it is to make these diodes on a large scale.

Lab results are not often easily translated to affordable consumer applications, though it does show possiblility.

Temperature tuning should not be neglected entirely either: If you can pack the laser and TEC in a good package such a system can reliably operate in a consumer product, albeit under limited temperature ranges.

The latter isn't that big of a problem, many consumer electronics don't work very well at temperatures a bit below freezing or over 50 celcius.
 

paul1598419

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CurtisOliver, your site on 626nm is not working. Tried to look at it and was told it isn't accessible.
 

CurtisOliver

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I'll try and fix it for you later Paul. Thanks for letting me know. :)

Benm, I agree that lab results usually don't lead into consumer products very quickly but it is possible. Whilst temperature tuning isn't impossible in a consumer product, it is not the most suitable compared to room temperature semiconductors. 580nm is quite far away from the 608nm observed at room temperature so it would have to be cooled quite substantially at the moment. But I have faith in this new semiconductor mixing as it is the closest so far to meeting the requirements for multiple applications, hence could acquire some funding. Let's hope to the future. I bet 626nm will be our next diode wavelength depending on whether or not any other discoveries are made.
 

Encap

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I'll try and fix it for you later Paul. Thanks for letting me know. :)

Benm, I agree that lab results usually don't lead into consumer products very quickly but it is possible. Whilst temperature tuning isn't impossible in a consumer product, it is not the most suitable compared to room temperature semiconductors. 580nm is quite far away from the 608nm observed at room temperature so it would have to be cooled quite substantially at the moment. But I have faith in this new semiconductor mixing as it is the closest so far to meeting the requirements for multiple applications, hence could acquire some funding. Let's hope to the future. I bet 626nm will be our next diode wavelength depending on whether or not any other discoveries are made.

RPMC sells 627nm 250mW and 350mW lasers diodes in a variety of mount types

See: http://www.rpmclasers.com/product/LDX%20445-690nm%20Laser%20Diodes.pdf
 

CurtisOliver

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In that case, 608nm then. :p
Thanks for the link Encap.

And I have given you the search term Paul, as the link won't get past the sites HTTPS server.
 
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Benm

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Notice that the operating temperature on those 627 nm diode is only 10 degrees celcius though.

I can't tell from the datasheet if that operating temperature is the temperature of the die or the outer case, but in either scenario these would have to be TEC cooled to work in "normal conditions" (20 or 25 degrees celcius depending on who you ask).
 




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