time-nuts@lists.febo.com

Discussion of precise time and frequency measurement

View all threads

Re: [time-nuts] advice

HM
Hal Murray
Wed, Feb 22, 2017 8:54 AM

If you have a dark fiber or 2 between the surface and the lab and a pair of
sufficiently stable lasers (one at the surface and one in the underground
lab) you could look at the change in beat frequency between the lasers
(around 50Hz for a pair of red lasers).

Interesting idea.  Thanks.

How stable is a good laser and/or how hard do I have to work (or how much do
I have to pay) to get one stable enough for this experiment?  What's the line
width on a typical laser?  How much does it wander with temperature and
supply voltage and phase of the moon?

--
These are my opinions.  I hate spam.

bruce.griffiths@xtra.co.nz said: > If you have a dark fiber or 2 between the surface and the lab and a pair of > sufficiently stable lasers (one at the surface and one in the underground > lab) you could look at the change in beat frequency between the lasers > (around 50Hz for a pair of red lasers). Interesting idea. Thanks. How stable is a good laser and/or how hard do I have to work (or how much do I have to pay) to get one stable enough for this experiment? What's the line width on a typical laser? How much does it wander with temperature and supply voltage and phase of the moon? -- These are my opinions. I hate spam.
AK
Attila Kinali
Thu, Feb 23, 2017 1:19 AM

On Wed, 22 Feb 2017 00:54:34 -0800
Hal Murray hmurray@megapathdsl.net wrote:

How stable is a good laser and/or how hard do I have to work (or how much do
I have to pay) to get one stable enough for this experiment?  What's the line
width on a typical laser?  How much does it wander with temperature and
supply voltage and phase of the moon?

A normal ECDL system gets a line width sub 1MHz pretty easily, the better
ones are in the order of 10-100kHz. With the right stabilization system
sub 1Hz linewidths can be achieved [1,2]. Stability is in the order
of 10^-14 to 10^-16 (ADEV/MDEV) from 1s to a few 100s. Long term seems
to be limited by temperature stability, creep of spacer material and
mirror aging (no particular order).
I haven't had a look at this topic in a while so I cannot tell you
what the current state of the art is.

		Attila Kinali

[1] "Sub-hertz-linewidth diode laser stabilized to an ultralow-drift
high-finesse optical cavity", by Hirata, Akatsuka, Ohtake, Morinaga,
2014
http://dx.doi.org/10.7567/APEX.7.022705

[2] "A sub-40-mHz-linewidth laser based on a silicon single-crystal
optical cavity", Kessler, Hagemann, Grebing, Legero, Sterr, Riehle,
Martin, Chen, Ye, 2012
http://dx.doi.org/10.1038/nphoton.2012.217

--
It is upon moral qualities that a society is ultimately founded. All
the prosperity and technological sophistication in the world is of no
use without that foundation.
-- Miss Matheson, The Diamond Age, Neil Stephenson

On Wed, 22 Feb 2017 00:54:34 -0800 Hal Murray <hmurray@megapathdsl.net> wrote: > How stable is a good laser and/or how hard do I have to work (or how much do > I have to pay) to get one stable enough for this experiment? What's the line > width on a typical laser? How much does it wander with temperature and > supply voltage and phase of the moon? A normal ECDL system gets a line width sub 1MHz pretty easily, the better ones are in the order of 10-100kHz. With the right stabilization system sub 1Hz linewidths can be achieved [1,2]. Stability is in the order of 10^-14 to 10^-16 (ADEV/MDEV) from 1s to a few 100s. Long term seems to be limited by temperature stability, creep of spacer material and mirror aging (no particular order). I haven't had a look at this topic in a while so I cannot tell you what the current state of the art is. Attila Kinali [1] "Sub-hertz-linewidth diode laser stabilized to an ultralow-drift high-finesse optical cavity", by Hirata, Akatsuka, Ohtake, Morinaga, 2014 http://dx.doi.org/10.7567/APEX.7.022705 [2] "A sub-40-mHz-linewidth laser based on a silicon single-crystal optical cavity", Kessler, Hagemann, Grebing, Legero, Sterr, Riehle, Martin, Chen, Ye, 2012 http://dx.doi.org/10.1038/nphoton.2012.217 -- It is upon moral qualities that a society is ultimately founded. All the prosperity and technological sophistication in the world is of no use without that foundation. -- Miss Matheson, The Diamond Age, Neil Stephenson