
World's first white laser - ChuckMcM
https://asunews.asu.edu/20150728-worlds-first-white-laser
======
toufka
Reddit discussion with the author is pretty good [1]. The author tries to
dispel some of the superlatives in the public statements about the work, and
provides good detail about what they've done: a novel way to produce a single
material ("nanosheet") that when pumped, emits at multiple (three gets you
white light, and what they did here) wavelengths.

[1]
[https://www.reddit.com/r/science/comments/3f0oyo/the_first_w...](https://www.reddit.com/r/science/comments/3f0oyo/the_first_white_laser_scientists_and_engineers_at/)

> Actually, there are a few key points we wanted to make with this paper.
> First, yes this is semiconductor-based, which offers a few advantages over
> optical fiber technology. The second is that this was accomplished in a
> single growth run, unlike several other devices we cite which essentially
> just run multiple lasers in parallel. Third, the growth mechanism for these
> nanosheets is novel. Also, as far as we could tell, we provided the first
> direct evidence for the nanobelt-nanosheet conversion mechanism. It had been
> previously proposed before in a single paper, but did not have any
> experimental evidence to back up the claim.

> Also, the linked article is somewhat sloppy. We are by no means reporting
> the first ever white laser, and in fact we cite several examples of previous
> setups used to produce white lasing. In this paper we report the first
> monolithic, semiconductor-based laser.

~~~
TeMPOraL
Thank you for linking that.

That's why I love Hacker News and some subreddits. Whenever there's an
interesting story in the news, it's usually full of misinterpretations and
sometimes outright lies. But on their HN/Reddit discussion threads you can
often meet people who are either directly involved in the project or know
someone who is first-hand, who can cut through the bullshit and say how things
actually are.

------
zik
Unfortunately this isn't the world's first white laser. They've been around
for a few years and they're sold by a few companies.

[http://www.leica-microsystems.com/science-lab/white-light-
la...](http://www.leica-microsystems.com/science-lab/white-light-laser/)

[http://www.nktphotonics.com/product_cat/supercontinuum-
laser...](http://www.nktphotonics.com/product_cat/supercontinuum-
lasers/?gclid=Cj0KEQjw8-GtBRCMl7m54PzgjNQBEiQAIZckv_HDk4dhHk8m949RhZJqmnWEKYm2sPBEc2Zh8H050QoaAszW8P8HAQ)

Apparently this discovery is actually the first _semiconductor_ white light
laser, which is pretty neat - but not what the headline claims.

~~~
Schwolop
Unless I'm misunderstanding (which I could well be - this isn't my field!)
those use several narrow-band coloured lasers and combine the output. This
article is a single wide-band semiconductor.

~~~
steve19
According to the article they generate three lasers from the same silicon. I
think the benefits are size and/or simplicity, cost etc.

~~~
Schwolop
Ah ok, thanks for clarifying.

------
prewett
Interesting, although a bit light on details. From the article it would seem
like the laser is essentially three lasers (red, green, blue) coupled
together, and by changing the amount of R, G, and B you tune the color. I'm
curious how coherent the R, G, and B are with each other. A true "white" laser
would be coherent on all frequencies, but I'm guessing that's pretty hard to
accomplish (so limited holography uses).

I question the claim that "lasers are brighter, [and] more energy efficient
[than LEDs]," though. I'm assuming LEDs are much more efficient (more lumens
of output per watt of input), but I'd believe that the laser might be more
intense (more lumens/m^2). Typically lasers are pretty ineffient. [1] reports
efficiencies of 7% - 8.9% with semiconductor lasers. Wikipedia [2] appears to
be reporting LED efficiencies of 20% - 39%, and one research group [2] reports
on getting over 100% efficency, with an LED emitting "more optical power than
the electrical power it consumes," although at very low power levels.

[1]
[http://www.laserfocusworld.com/articles/print/volume-48/issu...](http://www.laserfocusworld.com/articles/print/volume-48/issue-08/world-
news/semiconductor-lasers-green-laser-diode-emits-at-536-nm.html)

[2] [https://en.wikipedia.org/wiki/Light-
emitting_diode#Efficienc...](https://en.wikipedia.org/wiki/Light-
emitting_diode#Efficiency_and_operational_parameters)

[3]
[http://phys.org/news/2012-03-efficiency.html](http://phys.org/news/2012-03-efficiency.html)

~~~
sigterm
Not sure what you mean by "how coherent the R, G, and B are with each other".
They are not coherent, since they have different frequencies.

~~~
fsilva
FWiW you can have 3 or even more frequencies in a laser beam coherent with
each other, i.e. where te phase of the waves is locked together. This allows
you to interfere the waveforms of the different lasers in time, as their
relative phases are locked. This is very hard to do with continuous wave
lasers, but rather routine with short pulsed lasers (e.g. femtosecond).

------
ChuckMcM
The actual paper is behind the Nature paywall but this development is pretty
important. Modulating a white laser would make it _much_ easier to pick up a
reliable signal, imagine an AM radio transmitter that transmitted on every
frequency of the AM band, even the crappiest tuner would give you a clear
signal.

Given that it makes it an excellent candidate for intra-satellite
communications. Imagine satellite clusters which can effectively be very large
aperture sensors if they know their exact relationship to each other and can
communicate with picosecond accuracy. Very cool.

~~~
Schwolop
I like the idea of LiFi communications. Might be hard for devices to upload
data, but beaming stuff from your light bulbs down to your devices might be a
very high bandwidth possibility.

My imagination is getting ahead of me, but you could potentially have
lightbulbs+LIDAR in your roof, to track occupants and things.

~~~
CHY872
The current issue is because light is line-of-sight. Such systems
traditionally need a lanyard of some kind to provide unobstructed access, and
this is super inconvenient for the user.

Then there's the problem of means-of-detection; Phillips had a cool setup that
relied on the rolling shutter of phone cameras; but as soon as someone comes
up with a global shutter for phones, such systems are toast.

------
fiveoak
Here's a link to the actual journal article in Nature:
[http://nature.com/articles/doi:10.1038/nnano.2015.149](http://nature.com/articles/doi:10.1038/nnano.2015.149)
(unfortunately probably pay-walled)

------
userbinator
_Lasers are brighter, more energy efficient, and can potentially provide more
accurate and vivid colors for displays like computer screens and televisions_

Brighter is not necessarily a good thing. I've noticed a trend of monitors
increasing in brightness over the years, and my current pair of monitors which
is already a few years old is more than bright enough at the lowest (0)
brightness setting - I've turned it down from the eye-watering maximum it was
set to when I got them, and left it there ever since. I don't think we need
more brightness in ordinary monitors; maybe niche applications like outdoor-
readable displays would benefit. At the very extreme, it causes the eye damage
well known of high-power lasers.

~~~
vacri
> _applications like outdoor-readable displays_

A few years ago I saw Andrew Tridgell talk about his current plaything:
autopiloted model aircraft (using a linux project whose name I can't recall).
Anyway, as the aircraft were used outdoors, he needed a laptop bright enough
to use in sunlight.

After much faffing about, he settled on simply taking the plastic back and
lighting panel off a normal laptop, and simply letting the ambient sunlight
shine through the LED panel. We saw it in use later out on the field, and it
worked pretty well. Of course, it's not going to work for night use...

~~~
dharma1
That's a great idea :)

The project Tridge is working on is ardupilot -
[https://github.com/diydrones/ardupilot](https://github.com/diydrones/ardupilot)

------
fffrad
... And we are not going to show you any pictures except a 232x309 small
consolidated jpeg.

~~~
Reefersleep
So many scientific articles cause this response in me. "Invention X causes
fantastic visual product Y". Alright alright, talk at length about X all you
want, but for the love of internet kittens, show me Y!

------
logfromblammo
One application I can think of would be bouncing RGB colors off of three
digitally modulated mirrors (like the Texas Instruments DLP chip), then
combining the reflected beams into one. You could project a movie onto a
screen from a mile away.

It seems like this could also be used for cheaper tri-color (or quad-color)
holography. Such features are used as security elements in passports and
banknotes.

------
Polarity
thats racist

