[time-nuts] laser as clock source

Bruce Griffiths bruce.griffiths at xtra.co.nz
Sat May 7 03:45:46 EDT 2016


No, laser photon count statistics are Poissonian. There are fluctuations in photon detection rate. The distribution of photon energies is narrow (for a single spatial and temporal mode laser).
Bruce
 

    On Saturday, 7 May 2016 6:01 PM, Ilia Platone <info at iliaplatone.com> wrote:
 

 Wait... no telescopes, very close distances...

only a laser, with a photon limiter like a dark window, "close" like 
10mm or so... just the space required for the laser optics plus the 
"limiter", and a photon counting detector that can be an APD or a PMT, 
it depends on the size required and scale of integration.

The "idea" came because my professor told me that laser is a light 
source composed by a limited number of harmonics, so close the ones as 
some nm wavelengths, to get these lights can be directional and 
manouverable: if these should be the carachteristics of lasers (a laser 
expert can correct me), photons emitted by this type of light source 
should hit the detector at a constant rate. The (very dark) limiter 
serves to regulate the photon flux so a very limited number of photons 
reach the sensor part.

The question was if the photodetector could use the individual photon 
detection as clock tick, and if these ticks can be regular in frequency. 
Many have replied that it would be noisy: phase noise? I don't think a 
single photon can cause AM noise, because I was talking about single 
photon pulses into the photon counting region, not into the analog 
region. Please correct me if I'm wrong.

Ilia.


Il 05/05/2016 21:22, Hal Murray ha scritto:
> jimlux at earthlink.net said:
>> Well, in deep space optical comm, we send many photons with a laser, and  we
>> use pulse position modulation at the receiver detecting single  photons (or
>> "few photons"), by which we can send "many bits/photon"  (e.g. if you have
>> 256 possible time slots in which the photon can  arrive, you have 8 bits/
>> photon)
> Neat.  Could you please say a bit more.
>
> What sort of distance?  Bandwidth?  Error rate?
>
> How big is the laser and telescope?  What sort of optics on the receiver?
> How hard is it to point the receiver in the right direction?  How hard is it
> to point the transmitter telescope?  ...
>
> How does the receiver get timing?
>
>

-- 
Ilia Platone
via Ferrara 54
47841
Cattolica (RN), Italy
Cell +39 349 1075999

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