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back to article Wonder substance pulses QUADRILLION lasers per second

Light covers a very wide spectrum, making its potential communications capacity nearly infinite, so why does the world stick to a few wavelengths for communications? The reason is that currently available amplifier components only work in the 1330 and 1550 nm wavelengths. However, adding yet another string to its already- …

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"Is there anything Graphene can't do?"

Make a decent cup of tea?

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Silver badge

Re: "Is there anything Graphene can't do?"

"Make a decent cup of tea?"

Glad to be of service, Share and Enjoy.

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Anonymous Coward

Re: "Is there anything Graphene can't do?"

"With no band gap, graphene can contain electrons across a continuum – meaning it can absorb light across a continuum."

Er, no. That statement is fundamentally wrong.

Any material having "no band gap" really means the Fermi energy is in a band rather than in a band gap, and if so, means the material is a metal an will reflect light below it's plasma frequency and absorb light above its plasma frequency. Whether it can be used as a laser medium depends on other attributes, which is why you don't see solid metals used as laser medium.

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Silver badge

Re: "Is there anything Graphene can't do?"

Where the hell is my space elevator? The focus needs to be on making graphene rope.

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Anonymous Coward

Is there anything Graphene can't do?

Play Crysis on full?

Beat sense into an EDL member?

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Re: Is there anything Graphene can't do?

Get a user to remember their password?

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Re: Is there anything Graphene can't do?

"Play Crysis on full?

Beat sense into an EDL member?"

Now now, we know there are machines that can play Crisis flat-out, don't be silly.

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Re: Is there anything Graphene can't do?

I think they're working on graphene-based processors, so the Crysis one might happen.

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Paris Hilton

Hold on!

These are short pulses, so how can they be "lasers?" The shortness alone guarantees that a very wide band of frequencies will be in the pulse.

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Yag

Re: Hold on!

I have trouble to understand your reasonment, especially the "short pulses = not a laser" part...

Care to elaborate a bit to enlighten a Philistine?

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Holmes

Re: Hold on!

A "laser" should work on a narrow peak of frequencies, otherwise it's just a (white) light.

As you take the signal in the time domain over to the frequency domain, you will notice quite naturally that:

Long-time-signals can have very narrow peaks in the frequency domain.

Short-time-signals necessarily have very broad bumps in the frequency domain.

Until you reach the dirac function which has no extension in one, but infinite extension in the other domain.

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Go

Re: Hold on!

Think about the short-pulse as the sum of many laser different laser frequencies, emitted from the same laser cavity. All the phase-locked frequencies sum up to a very short pulse. It's still light amplification by stimulated emission of radiation, only at more than one discrete frequency.

The trick is to get all frequency contributions phase-locked. The work described here does not actually talk about graphene as lasing material (it wouldn't work, see post below), but as a 'saturable absorber' that will eat away all non-phaselocked light contributions. Therefore, graphene is not lasing, but helps to build short pulse lasers.

The story here is highly misleading in implying that there is an actual 'graphene laser'. The referenced nature story is only mildly misleading and only says that 'Ultrashort laser pulses [are] squeezed out of graphene'. The proper scientific publications cited in nature (here and here) only mention that graphene is a saturable absorber and helps to mode-lock short-pulse lasers. Infinite dilution of information via 3 degrees of separation :).

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Happy

Re: Hold on!

I'm sure that someone called 'Yag' would know a lot about lasing.

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Thumb Up

Re: Hold on!

Indeed: the suggestion is for graphine to act within a short-pulse laser system, not to be a lasing material itself. The odd thing in such systems is that you only have to make some beam directions/frequencies/phases less easy to traverse the resonating cavity than the rest, and the lasing material (whatever that is) will put most of its energy into the easy routes (via positive feedback of the stuff that gets though most easily).

As pointed out by a few, you can't have a single frquency and be a short pulse at the same time: a short pulse requires a range of phase-locked frequencies. But the definition of a laser can cope with that.

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Yag
Happy

Re: Hold on!

No relation but...

Actually, I worked for a few month in an holographic studio, and they used a few pulsed lasers there - it's a bit less aggressive when trying to take holographic portraits of people.

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Stop

I see a little problem

Lasers require something called 'population inversion' to work. In a nutshell, you must be able to pump energy into the lasing material and the material must hold onto that energy until some light comes along and gets amplified by stimulated emission of that energy (Laser: Light Amplification by Stimulated Emission or Radiation). To store the energy, the laser material needs some stable energetic state. If there is no bandgap, I can't see how such a stable state should exist. There will be no graphene laser, you've been had.

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For this, I'm going to like carbon on Facebook

And hope it gets a few more followers on Twitter.

Now that's social.

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Re: For this, I'm going to like carbon on Facebook

"For this, I'm going to like carbon on Facebook "

Yur Carbon sux, loooser!

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Can you attach it to frickin' sharks?

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Holmes

You could. But it would cost one hundred beeeeelion dollars.

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why does the world stick to a few wavelengths for communications?

Because the low-loss wavelength ranges in silica, the primary material used in optical fibres, are at about 1330 and 1550 nm. The amplifiers are designed largely to match these.

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Bronze badge

Re: why does the world stick to a few wavelengths for communications?

THANK you. Now I don't have to add this.

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Devil

Is there anything graphene can't do?

Make it into an actual product you can buy?

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Go

Re: Is there anything graphene can't do?

good troll, well done. Would be trolled again!

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Emo
Go

Did anyone else think of Q or was it just me?

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Unhappy

So where is this wonderous stuff?

I have been hearing about graphene and how it will work wonders for so long now that I have turned skeptical of the claims being made about it. Why doesn't some stop looking at what it can do and start trying to find a way to produce it? It is time to put up or shut up!

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