A new way to make laser-like beams | Hacker News Reader

A new way to make laser-like beams

ns.umich.edu

39 pointskevbin13 comments

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)

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.

Ok, we'll take that 250x bit out of the title.

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).

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?

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.

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.

At 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.

Yes you're basically right, but it is (perhaps unfortunately) a common way to express it in English. I.e. 2x fewer calories would imply 1/2 as many calories, 5x faster would imply 1/5th the time, etc.

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?

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?

Could this make laser ignition fusion practical?

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

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