

A new way to make laser-like beams - kevbin
http://ns.umich.edu/new/releases/22218-a-new-way-to-make-laser-like-beams-using-250x-less-power

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kken
Misleading title. Semiconductor lasers are in general already >30% efficient
there is no way to make a laser 250x more efficient. The researchers only
improved a special type of laser (polariton laser)

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gnoway
I didn't get that this was supposed to be 250x more efficient, just that it
required ~250x less energy and was potentially more efficient.

It reads like there is a minimum amount of energy required to establish and
maintain a laser beam using similar materials today, and they have lowered
that minimum threshold by a factor of ~250. The resulting
energy/intensity/whatever of the beam vs. the ongoing input energy is not
discussed in the article.

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smoyer
Increasing the efficiency of semi-conductor lasers has huge ramifications as
output powers increase. In the cable industry, you can put >110 channels of
analog video across a fiber optic link, but the laser has to be cooled via a
peltier device since the point heat at the die and cavity is so intense. It
will be interesting to see whether we can also improve the modulation index
with this type of device (for wideband communications like CATV, it's limited
by the linearity of the device).

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kristopolous
Fairly unimportant question about the English but wouldn't "250x less" be
-249, as in -(250x more)? If this is true, then, shouldn't the claim be
"0.996x less"?

Surely someone would say "99.6% less" and 99.6% = 0.996. 250x would then =
25,000%. 25,000% less isn't likely a valid value here.

Am I missing something?

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DavidSJ
This sort of language is routinely abused in a confusing manner. Usually when
someone means "200% more/bigger/faster", they say "3x more/bigger/faster",
instead of "3x as much/big/fast" like they should. At least in this case
there's not really any ambiguity unless you think it's possible to spend
negative energy.

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ewzimm
3x more would definitely be interpreted as 4x the original value. If a product
was advertised as three times faster when it was only three times as fast,
there would be legal issues with false advertising.

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DavidSJ
At [http://www.apple.com/mac-pro/performance/](http://www.apple.com/mac-
pro/performance/) , Apple advertises Thumderbolt 2 as 25x faster than FireWire
800. Thunderbolt 2 has bandwidth of 20 Gbps, which is 25 times FireWire 800's
800 Mbps.

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jmpe
Anyone know what material the mirrors are made from? I'm surprised that the
configuration is a horizontal device with the mirrors vertical, I'd assume a
vertical device would be easier.

Edit: hmm, on second thought, a vertical device would have the electrode
vertical as well and it's probably metal. Maybe a polysilicon electrode?

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zwieback
Is this about efficiency or threshold current? Not totally clear. It sounds
like it's about threshold but doesn't mention the efficiency so what happens
if you have lots of these lasers integrated into a circuit to replace
traditional transmission lines or connectors?

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mrfusion
Could this make laser ignition fusion practical?

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kylek
Was wondering about this too - if it scales up to something NIF-sized. The
article only talks about low-power/IC applications.

