speed of light
laura
I need a device which can measure the fluctuations, in a light ray,
with the speed of light.
I mean, I need to know if at second 10^-8 (ten to power minus 8) I have
a fluctuation in a light ray. I'm not interested to compute the power
of that ray. I'm just interested to know if at a given moment in time
(very, very small) it was or not a fluctuation in the intensity of that
ray.
Is this possible?
Thanks,
Laura
Rene Tschaggelar
Within limits yes. First you need a sufficiently fast
and sensitive sensor. If this sensor is delivering a
still measureable current diffeence then the electronics
can do it.
Rene
--
Ing.Buero R.Tschaggelar - http://www.ibrtses.com
& commercial newsgroups - http://www.talkto.net
laura
complicated path. Sometimes, the ray will be splitted into 2 rays and
each of them will follow some path.
All rays have the same destination, but they will reach there at
different moments in time (probably), depending on the length of the
path that they have followed.
I know the exact moment when a particular ray should get to the
destination, but I need to know if it actually got there (or it has
got stuck somewhere on the path).
This is why I need some device, which can tell me if there is a
fluctuation in the light, at the destination point, at a given moment
in time (that moment must be specified with high precision ~ 10^-9).
If I have a fluctuation in the signat at that moment I know for sure
that the particular ray which I was expecting has arrived there.
Thanks,
Laura
Phil Allison
"laura" <laura.b...@gmail.com>
** Blatant Troll.
** No problem babe !!!
There are heaps of Martian Engineers just waiting to supply you with a
missing photon detector.
Those cute, green alien dudes know all about pesky, random, micro size black
holes eating up innocent, unwary photons for several millennia.
This outrage has got to stop !!!!
When a cute photon says no - it means no.
........ Phil
Winfield Hill
Optical sensors with 1ns response time are readily available.
--
Thanks,
- Win
Anthony Fremont
"Phil Allison" <phila...@tpg.com.au> wrote in message
news:3sp45hF...@individual.net...
So you don't think she is the L. Brandusan that researches metallurgy?
Phil Allison
"Anthony Fremont"
> "Phil Allison"
>>
>> ** Blatant Troll.
>
> So you don't think she is the L. Brandusan that researches metallurgy?
** Why should I - or care ?
The post was a troll.
.......... Phil
laura
I'm a computer scientist.
best regards,
L
Fred Bloggs
Why don't you use two detectors at the receive end?
bill....@ieee.org
If you are working with bright lasers, and can expect to see lots of
photons within your critical sub-nanosecond time interval, life is
pretty straightforward.
If you are in the position to have to detect whether there was one
photon there from time to time you need a single-photon detector, and
it could be worth your while to read "Performance otimisation of active
quenching circuits for picosecond timing with single photon avalanche
diodes" by A. Lacaita, S. Cova, C, Smaori and M. Ghioni in Rev. Sci.
Instrum. volume 66 pages 4289-95(1995). Sergio Cova really does know
what he is talking about, and over the years he has published an
interesting series of papers on the subject in Rev. Sci. Instrum. and
Applied Optics. I've got his e-mail address - it is ten years since
I've used it, but he still seems to be publishing steadily.
---------
Bill Sloman, Nijmegen
redbelly
Phil Allison wrote:
> The post was a troll.
Seems pretty obvious to me too. Anybody who uses language like the OP
does not stand a chance in hell of setting up and using a laser,
optical beamsplitters, and photodetectors.
Mark
laura
Thanks for you advice.
I don't want to implement the device now.
Right now I'm looking for some possible solutions which could help me.
You say that if I use some bright lasers things are easier? Could you
give me some more details about that?
I don't plan to use only one photon.
Thanks,
L
o...@uakron.edu
laura wrote:
> Dear Bill,
>
> Thanks for you advice.
>
> I don't want to implement the device now.
> Right now I'm looking for some possible solutions which could help me.
>
> You say that if I use some bright lasers things are easier? Could you
> give me some more details about that?
Search " laser autocorrelator", and modify that technique, ie run your
two laser pulses (assuming your using a picosecond or other pulsed
laser) into a second harmonic generating crystal, when you have a
maxima from the doubled light, your pulses are in phase. This is easy
to do with common IR lasers, you havent told us about your light
source, which makes a big difference of how you go aboput this.
probably time to find a skilled physics person, too!
your really tryint to look at the leading edges of your light pulse,
aren't you?
Quantum Computing?
Steve Roberts
Winfield Hill
>
> I don't plan to use only one photon.
You could though, if you wished, at least with respect
to timing its arrival to under a nansecond.
--
Thanks,
- Win
laura
I mean, the problem is that if I use only one photon, maybe it's hard
to be detected...
And what happens if the photon is divided into 2 photons? Is this
possible?
Sometimes, in my device I need to do this. And the photons will go on
different paths. And some of them will get earlier to the destination
and others will get later....
laura
some solutions to my problem. What I know is that I send a signal
(probably a light ray) into some device... the light will be divided
into some nodes of the device and because of that I will have multiple
rays at the destination. But I know the moment when a particular ray
will arrive there. I need only to know whether that particular ray has
arrived there (or it was stuck somewhere).
Do you think that I could use another kind of signal (instead of
light). At a theoretical level I work with signals, but if I want to
make an implementation probably (???) the light is the best.
Any suggestions are welcomed !
Thanks,
L
Phil Allison
"redbelly"
** The same odd question was posted on "sci.physics" by the same "laura" a
few minutes before here.
The name and email addy have not been used on usenet before.
Walks like a duck .......
......... Phil
bill....@ieee.org
laura wrote:
> I don't mind to use only one photon.
>
> I mean, the problem is that if I use only one photon, maybe it's hard
> to be detected...
>
> And what happens if the photon is divided into 2 photons? Is this
> possible?
Not that I know of - at least not in any useful way. Non-linear
crystals allow frequency-doubling, where two photon fuse to make one
photon of twice the frequency (half the wavelength), but I don't think
that works the other way around. In theory, you could hit a molecule
with the right energy to promote it into a energy state that was two
quantum steps above the ground state, and hope that it would emit two
photons in the process of relaxing back to the ground state, but this
isn't an instantaneous process.
> Sometimes, in my device I need to do this. And the photons will go on
> different paths. And some of them will get earlier to the destination
> and others will get later....
Are you thinking about quantum cryptography? Page 18 of the review
below
discusses single-photon detectors ....
http://arxiv.org/PS_cache/quant-ph/pdf/0101/0101098.pdf
----------
Bill Sloman, Nijmegen