# Talk about cutting-edge technology! Boffins fire world's sharpest laser

A team of physicists claims to have created the world's sharpest laser, with a line width frequency of only 10 millihertz – opening up the possibility of improving the accuracy of optical clocks and radioastronomy experiments. Lasers are, ideally, a concentrated stream of photons at a single frequency. But in reality the light …

1. "approximately 200 trillion times per second" , "about 10 times the distance between the Earth and Moon."

What are you talking about? Please explain these values in proper el Reg speak.

1. baw hair

2. a) ~200THz is an unusual way to say 1.5µm

b) ~0.33EBs (~0.33 quintillion beard-seconds), I think-- but I just made up the symbol so Bs may in fact be BS, and Bob's your uncle

1. #### beard-seconds

@dbtx

I just wasted far too much time on the page you linked to!

"The light waves of the laser oscillate approximately 200 trillion times per second, and are stable for about 11 seconds before they get out of sync. By then, the wave has reached a length of approximately 3.3 million kilometres – about 10 times the distance between the Earth and Moon."

2. "key to taking measurements in radio astronomy"

Not to mention allowing me to more accurately play with my cat.

1. Wait, what? Cats can see infrared?!?

1. Wait, what? Cats can see infrared?!?

Cats can see *everything*. And back it up to long-term storage for blackmail^Wpersuasion purrposes..

3. #### Would this help?

With Hawking and Milners ideas for a laser powered set of micro seed-ships to alpha Centauri?

https://www.theregister.co.uk/2016/04/12/yuri_milner_stephen_hawking_interstellar_space_mission/

At least get the 'ball rolling'.....

Regards

F00

4. #### Of course the real question

Is when can these be mounted on sharks

1. #### Re: Of course the real question

"We're gonna need a more stable shark"

1. #### Re: Of course the real question

"We're gonna need a more stable shark"

Maybe now is a good time to retrain as a shark psychologist then?

5. #### This is confusing

"Lasers are, ideally, a concentrated stream of photons at a single frequency."

"The light waves of the laser oscillate ..."

Make your mind up. Which one is it?

1. #### Both at the same time

It's all gone a bit quantum.

2. #### Re: This is confusing

"Which one is it?"

Well, the scientifically accurate answer to this question is: Yes.

6. #### It's going to cause problems......

Oh crap! This is going to have the Vogon's reading us their poetry as a reward for lasering their spaceships as they build the hyperspace bypass.

Mine's the one with the Douglas Adams earplugs in the pocket.

7. Apparently Reg readers don't know the value of a properly tuned laser. Is everyone here just for the girly pics, and sharks?

1. Of course, don't you know that The Register is a well-known lesbian publication?

https://www.theregister.co.uk/2008/05/06/indy_reg/

8. #### What is the point?

You're all missing the point. The word 'laser' is actually an acronym - Light Amplification by the Stimulated Emission of Radiation.

If they're after particularly fine stimulation leading to emissions, I know of a certain website. It wouldn't take them 10 years either.

1. #### Re: What is the point?

If you get it to amplify light with that you *are* indeed heading for a Nobel price, because the assembled power of Internet users would give us enough light to completely overload any solar panel on the planet..

9. Paragraph 1: < 10 mHz "line width frequency" - whatever a line width frequency is.

Paragraph 8: the frequency can vary by less than 0.4 aHz

I'm confused.

1. "Paragraph 1: < 10 mHz "line width frequency" - whatever a line width frequency is.

Paragraph 8: the frequency can vary by less than 0.4 aHz

I'm confused."

El Reg is also confused. The line width frequency is essentially the variation in frequency within the laser pulse, which is correctly reported as <10 mHz (it actually says "as small as 5 mHz" in the abstract). The 4*10^-17 is not a frequency at all as El Reg suggests, it's what they call the "flicker noise floor", which is essentially the ratio of linespread to laser frequency, so ~5 mHz / 194 THz. Since it's a ratio, it has no units.

10. #### IOW it's at 200THz but deviates from the exact number by +/- 0.01 Hz

IE 1 part in 20 000 trillion.

Which is pretty impressive.

and they hope to get it 10x better still.

Congratulations to all concerned.

11. So you'd be able to spin a CD on the moon and read it with a pickup on Earth providing the spot size was also constrained.

1. I propose trying this with Pink Floyd's dark side of the moon.

Though I'm not going to debate the correct sound system.

1. Though I'm not going to debate the correct sound system.

I refer the Honourable Commentard the the opus from Messrs. Flanders and Swann entitled "A Song of Reproduction".

Especially the line "you get flutters in your bottom"..

2. "Though I'm not going to debate the correct sound system."

Just borrow the one Disaster Area use.

2. #### @ Doctor Syntax

Actually, you just touched on my thought upon reading this, does the linewidth have an effect on beam spread?

I would imagine that constraining the the frequencies would increase coherence, which would limit the spread; this is reinforced by the use of the adjective "sharp".

1. #### Re: @ Doctor Syntax

"I would imagine that constraining the the frequencies would increase coherence"

I interpret "Stable for up to 10x the distance from Earth to Moon" as referring to the coherence length so that appears to be the case.

The irony is, of course, that a laser should be unnecessary for reading CDs & DVDs. Interference contrast ( https://en.wikipedia.org/wiki/Differential_interference_contrast_microscopy ) microscopy resolves similar phase differences with white light.

3. "So you'd be able to spin a CD on the moon and read it with a pickup on Earth providing the spot size was also constrained."

This just triggered an intense "WOW" moment just now.

12. #### The future is here

Does this mean we will finally get a phased plasma rifle in the 40-watt range?

13. #### spukhafte Fernwirkung

I can't but wonder if this achievement will not also benefit work on creating entangled photons and sending them over large distances, as described here ?...

Henri

14. #### No coherence! Please try harder.

I think the author is actually talking about the monochromatic photons being coherent* in a laser beam and how the coherence has been improved. However the article fails to mention this or make too much sense without it. Needs to try harder is my rating.

* Given that by its nature a laser beam is monochromatic (all photons of the same frequency or wavelength, if you prefer), what makes a it a laser is that the photons are coherent (in step or in-phase with each other) and it is this that makes the beam more powerful than say a monochromatic sodium vapour bulb in front of a parabolic mirror.

1. #### Re: No coherence! Please try harder.

One of the lecturers at uni told us to picture a laser beam as "a million identical red VW beetles driving at exactly the same speed and at exactly the same distance from each other through a staight tunnel".

2. #### Re: No coherence! Please try harder.

"a laser beam is monochromatic (all photons of the same frequency or wavelength, if you prefer)"

The word linewidth itself seems to disagree. [I thought that] the original idea of the line is that small bright place on a spectrogram, which is narrower or wider, indicating how energy is spread into the nearby frequencies. If they're strictly monochromatic, the linewidth is ideally zero. Two photons with an arbitrarily small difference between their frequencies will never have the same exact trajectory after going through a prism, and that's where linewidth physically comes from. What this has to do with coherence is that if one photon and another photon are at 2 frequencies with a nonzero difference between, then they simply cannot be in step, except they can briefly appear to be in step at some intervals corresponding to the beat frequency.

disclaimer (stoopid noobie alert): once upon a time I used to skip school and read a book about lasers at the public library, but that doesn't mean I know WTF I'm talking about

1. derp! s/step/phase/

3. #### Re: No coherence! Please try harder.

"Given that by its nature a laser beam is monochromatic"

No it isn't, try actually reading the article:

"Lasers are, ideally, a concentrated stream of photons at a single frequency. But in reality the light isn't perfectly monochromatic, as components in the laser introduce flicker noise that disturbs the beam's frequency, causing it to fluctuate. Most kinds of lasers have a line width of a few kilohertz to a few megahertz."

Also, coherency has nothing whatsoever to do with power. A laser beam is not any more powerful than "a monochromatic sodium vapour bulb in front of a parabolic mirror" - if both light sources are 10W, for example, then both have exactly the same power.

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