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?
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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
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